diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 6ca6793250..36b8db388a 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -185,6 +185,7 @@ jobs:
         - "arduino_nano_33_iot"
         - "arduino_zero"
         - "bast_pro_mini_m0"
+        - "bastble"
         - "bdmicro_vina_d21"
         - "bdmicro_vina_d51"
         - "bless_dev_board_multi_sensor"
@@ -311,6 +312,7 @@ jobs:
         - "sparkfun_samd21_mini"
         - "sparkfun_samd51_thing_plus"
         - "spresense"
+        - "stackrduino_m0_pro"
         - "stm32f411ce_blackpill"
         - "stm32f411ve_discovery"
         - "stm32f412zg_discovery"
@@ -343,8 +345,8 @@ jobs:
       run: |
         sudo apt-get install -y gettext
         pip install requests sh click setuptools awscli
-        wget https://adafruit-circuit-python.s3.amazonaws.com/gcc-arm-none-eabi-9-2019-q4-major-x86_64-linux.tar.bz2
-        sudo tar -C /usr --strip-components=1 -xaf gcc-arm-none-eabi-9-2019-q4-major-x86_64-linux.tar.bz2
+        wget --no-verbose https://adafruit-circuit-python.s3.amazonaws.com/gcc-arm-none-eabi-10-2020-q4-major-x86_64-linux.tar.bz2
+        sudo tar -C /usr --strip-components=1 -xaf gcc-arm-none-eabi-10-2020-q4-major-x86_64-linux.tar.bz2
     - name: Versions
       run: |
         gcc --version
diff --git a/devices/ble_hci/common-hal/_bleio/att.c b/devices/ble_hci/common-hal/_bleio/att.c
index 6528361cb1..4573d5e9ff 100644
--- a/devices/ble_hci/common-hal/_bleio/att.c
+++ b/devices/ble_hci/common-hal/_bleio/att.c
@@ -61,7 +61,7 @@ STATIC struct {
 typedef struct __packed {
     uint8_t properties;
     uint16_t value_handle;
-    uint8_t uuid[0];  // 2 or 16 bytes
+    uint8_t uuid[];  // 2 or 16 bytes
 } characteristic_declaration_t;
 
 STATIC uint8_t bleio_properties_to_ble_spec_properties(uint8_t bleio_properties) {
@@ -1010,21 +1010,22 @@ void process_read_group_req(uint16_t conn_handle, uint16_t mtu, uint8_t dlen, ui
 }
 
 int att_read_group_req(uint16_t conn_handle, uint16_t start_handle, uint16_t end_handle, uint16_t uuid, uint8_t response_buffer[]) {
-    struct __packed {
+
+    typedef struct __packed {
         struct bt_att_hdr h;
         struct bt_att_read_group_req r;
-    } req = { {
-            .code = BT_ATT_OP_READ_GROUP_REQ,
-        }, {
-            .start_handle = start_handle,
-            .end_handle = end_handle,
-        }
-    };
-    req.r.uuid[0] = uuid & 0xff;
-    req.r.uuid[1] = uuid >> 8;
+    } req_t;
 
+    uint8_t req_bytes[sizeof(req_t) + sizeof(uuid)];
+    req_t *req = (req_t *) req_bytes;
 
-    return send_req_wait_for_rsp(conn_handle, sizeof(req), (uint8_t *) &req, response_buffer);
+    req->h.code = BT_ATT_OP_READ_GROUP_REQ;
+    req->r.start_handle = start_handle;
+    req->r.end_handle = end_handle;
+    req->r.uuid[0] = uuid & 0xff;
+    req->r.uuid[1] = uuid >> 8;
+
+    return send_req_wait_for_rsp(conn_handle, sizeof(req_bytes), req_bytes, response_buffer);
 }
 
 STATIC void process_read_group_rsp(uint16_t conn_handle, uint8_t dlen, uint8_t data[]) {
@@ -1305,20 +1306,21 @@ STATIC void process_read_type_req(uint16_t conn_handle, uint16_t mtu, uint8_t dl
 }
 
 int att_read_type_req(uint16_t conn_handle, uint16_t start_handle, uint16_t end_handle, uint16_t type, uint8_t response_buffer[]) {
-    struct __packed {
+    typedef struct __packed {
         struct bt_att_hdr h;
         struct bt_att_read_type_req r;
-    } req = { {
-            .code = BT_ATT_OP_READ_TYPE_REQ,
-        }, {
-            .start_handle = start_handle,
-            .end_handle = end_handle,
-        }
-    };
-    req.r.uuid[0] = type & 0xff;
-    req.r.uuid[1] = type >> 8;
+    } req_t;
 
-    return send_req_wait_for_rsp(conn_handle, sizeof(req), (uint8_t *) &req, response_buffer);
+    uint8_t req_bytes[sizeof(req_t) + sizeof(type)];
+    req_t *req = (req_t *) req_bytes;
+
+    req->h.code = BT_ATT_OP_READ_TYPE_REQ;
+    req->r.start_handle = start_handle;
+    req->r.end_handle = end_handle;
+    req->r.uuid[0] = type & 0xff;
+    req->r.uuid[1] = type >> 8;
+
+    return send_req_wait_for_rsp(conn_handle, sizeof(req_bytes), req_bytes, response_buffer);
 }
 
 STATIC void process_read_type_rsp(uint16_t conn_handle, uint8_t dlen, uint8_t data[]) {
diff --git a/devices/ble_hci/common-hal/_bleio/hci_include/att_internal.h b/devices/ble_hci/common-hal/_bleio/hci_include/att_internal.h
index d6a4cb79c7..b8efccaf46 100644
--- a/devices/ble_hci/common-hal/_bleio/hci_include/att_internal.h
+++ b/devices/ble_hci/common-hal/_bleio/hci_include/att_internal.h
@@ -69,7 +69,7 @@ struct bt_att_info_128 {
 #define BT_ATT_OP_FIND_INFO_RSP			0x05
 struct bt_att_find_info_rsp {
 	uint8_t  format;
-	uint8_t  info[0];
+	uint8_t  info[];
 } __packed;
 
 /* Find By Type Value Request */
@@ -78,7 +78,7 @@ struct bt_att_find_type_req {
 	uint16_t start_handle;
 	uint16_t end_handle;
 	uint16_t type;
-	uint8_t  value[0];
+	uint8_t  value[];
 } __packed;
 
 struct bt_att_handle_group {
@@ -89,7 +89,8 @@ struct bt_att_handle_group {
 /* Find By Type Value Response */
 #define BT_ATT_OP_FIND_TYPE_RSP			0x07
 struct bt_att_find_type_rsp {
-	struct bt_att_handle_group list[0];
+        uint8_t _dummy[0];
+	struct bt_att_handle_group list[];
 } __packed;
 
 /* Read By Type Request */
@@ -97,19 +98,19 @@ struct bt_att_find_type_rsp {
 struct bt_att_read_type_req {
 	uint16_t start_handle;
 	uint16_t end_handle;
-	uint8_t  uuid[0];
+	uint8_t  uuid[];
 } __packed;
 
 struct bt_att_data {
 	uint16_t handle;
-	uint8_t  value[0];
+	uint8_t  value[];
 } __packed;
 
 /* Read By Type Response */
 #define BT_ATT_OP_READ_TYPE_RSP			0x09
 struct bt_att_read_type_rsp {
 	uint8_t  len;
-	struct bt_att_data data[0];
+	struct bt_att_data data[];
 } __packed;
 
 /* Read Request */
@@ -121,7 +122,8 @@ struct bt_att_read_req {
 /* Read Response */
 #define BT_ATT_OP_READ_RSP			0x0b
 struct bt_att_read_rsp {
-	uint8_t  value[0];
+        uint8_t _dummy[0];
+	uint8_t  value[];
 } __packed;
 
 /* Read Blob Request */
@@ -134,7 +136,8 @@ struct bt_att_read_blob_req {
 /* Read Blob Response */
 #define BT_ATT_OP_READ_BLOB_RSP			0x0d
 struct bt_att_read_blob_rsp {
-	uint8_t  value[0];
+        uint8_t _dummy[0];
+	uint8_t  value[];
 } __packed;
 
 /* Read Multiple Request */
@@ -142,13 +145,15 @@ struct bt_att_read_blob_rsp {
 
 #define BT_ATT_OP_READ_MULT_REQ			0x0e
 struct bt_att_read_mult_req {
-	uint16_t handles[0];
+        uint8_t _dummy[0];
+	uint16_t handles[];
 } __packed;
 
 /* Read Multiple Respose */
 #define BT_ATT_OP_READ_MULT_RSP			0x0f
 struct bt_att_read_mult_rsp {
-	uint8_t  value[0];
+        uint8_t _dummy[0];
+	uint8_t  value[];
 } __packed;
 
 /* Read by Group Type Request */
@@ -156,27 +161,27 @@ struct bt_att_read_mult_rsp {
 struct bt_att_read_group_req {
 	uint16_t start_handle;
 	uint16_t end_handle;
-	uint8_t  uuid[0];
+	uint8_t  uuid[];
 } __packed;
 
 struct bt_att_group_data {
 	uint16_t start_handle;
 	uint16_t end_handle;
-	uint8_t  value[0];
+	uint8_t  value[];
 } __packed;
 
 /* Read by Group Type Response */
 #define BT_ATT_OP_READ_GROUP_RSP		0x11
 struct bt_att_read_group_rsp {
 	uint8_t  len;
-	struct bt_att_group_data data[0];
+	struct bt_att_group_data data[];
 } __packed;
 
 /* Write Request */
 #define BT_ATT_OP_WRITE_REQ			0x12
 struct bt_att_write_req {
 	uint16_t handle;
-	uint8_t  value[0];
+	uint8_t  value[];
 } __packed;
 
 /* Write Response */
@@ -187,7 +192,7 @@ struct bt_att_write_req {
 struct bt_att_prepare_write_req {
 	uint16_t handle;
 	uint16_t offset;
-	uint8_t  value[0];
+	uint8_t  value[];
 } __packed;
 
 /* Prepare Write Respond */
@@ -195,7 +200,7 @@ struct bt_att_prepare_write_req {
 struct bt_att_prepare_write_rsp {
 	uint16_t handle;
 	uint16_t offset;
-	uint8_t  value[0];
+	uint8_t  value[];
 } __packed;
 
 /* Execute Write Request */
@@ -214,14 +219,14 @@ struct bt_att_exec_write_req {
 #define BT_ATT_OP_NOTIFY			0x1b
 struct bt_att_notify {
 	uint16_t handle;
-	uint8_t  value[0];
+	uint8_t  value[];
 } __packed;
 
 /* Handle Value Indication */
 #define BT_ATT_OP_INDICATE			0x1d
 struct bt_att_indicate {
 	uint16_t handle;
-	uint8_t  value[0];
+	uint8_t  value[];
 } __packed;
 
 /* Handle Value Confirm */
@@ -233,14 +238,15 @@ struct bt_att_signature {
 
 #define BT_ATT_OP_READ_MULT_VL_REQ		0x20
 struct bt_att_read_mult_vl_req {
-	uint16_t handles[0];
+        uint8_t _dummy[0];
+	uint16_t handles[];
 } __packed;
 
 /* Read Multiple Respose */
 #define BT_ATT_OP_READ_MULT_VL_RSP		0x21
 struct bt_att_read_mult_vl_rsp {
 	uint16_t len;
-	uint8_t  value[0];
+	uint8_t  value[];
 } __packed;
 
 /* Handle Multiple Value Notification */
@@ -248,19 +254,19 @@ struct bt_att_read_mult_vl_rsp {
 struct bt_att_notify_mult {
 	uint16_t handle;
 	uint16_t len;
-	uint8_t  value[0];
+	uint8_t  value[];
 } __packed;
 
 /* Write Command */
 #define BT_ATT_OP_WRITE_CMD			0x52
 struct bt_att_write_cmd {
 	uint16_t handle;
-	uint8_t  value[0];
+	uint8_t  value[];
 } __packed;
 
 /* Signed Write Command */
 #define BT_ATT_OP_SIGNED_WRITE_CMD		0xd2
 struct bt_att_signed_write_cmd {
 	uint16_t handle;
-	uint8_t  value[0];
+	uint8_t  value[];
 } __packed;
diff --git a/devices/ble_hci/common-hal/_bleio/hci_include/hci.h b/devices/ble_hci/common-hal/_bleio/hci_include/hci.h
index 5213edbf0f..797278946a 100644
--- a/devices/ble_hci/common-hal/_bleio/hci_include/hci.h
+++ b/devices/ble_hci/common-hal/_bleio/hci_include/hci.h
@@ -454,7 +454,7 @@ struct bt_hci_handle_count {
 #define BT_HCI_OP_HOST_NUM_COMPLETED_PACKETS    BT_OP(BT_OGF_BASEBAND, 0x0035)
 struct bt_hci_cp_host_num_completed_packets {
 	uint8_t  num_handles;
-	struct bt_hci_handle_count h[0];
+	struct bt_hci_handle_count h[];
 } __packed;
 
 #define BT_HCI_OP_WRITE_INQUIRY_MODE            BT_OP(BT_OGF_BASEBAND, 0x0045)
@@ -1099,7 +1099,7 @@ struct bt_hci_ext_adv_set {
 struct bt_hci_cp_le_set_ext_adv_enable {
 	uint8_t  enable;
 	uint8_t  set_num;
-	struct bt_hci_ext_adv_set s[0];
+	struct bt_hci_ext_adv_set s[];
 } __packed;
 
 #define BT_HCI_OP_LE_READ_MAX_ADV_DATA_LEN      BT_OP(BT_OGF_LE, 0x003a)
@@ -1158,7 +1158,7 @@ struct bt_hci_cp_le_set_ext_scan_param {
 	uint8_t  own_addr_type;
 	uint8_t  filter_policy;
 	uint8_t  phys;
-	struct bt_hci_ext_scan_phy p[0];
+	struct bt_hci_ext_scan_phy p[];
 } __packed;
 
 /* Extends BT_HCI_LE_SCAN_FILTER_DUP */
@@ -1189,7 +1189,7 @@ struct bt_hci_cp_le_ext_create_conn {
 	uint8_t      own_addr_type;
 	bt_addr_le_t peer_addr;
 	uint8_t      phys;
-	struct bt_hci_ext_conn_phy p[0];
+	struct bt_hci_ext_conn_phy p[];
 } __packed;
 
 #define BT_HCI_OP_LE_PER_ADV_CREATE_SYNC        BT_OP(BT_OGF_LE, 0x0044)
@@ -1354,7 +1354,7 @@ struct bt_hci_evt_role_change {
 #define BT_HCI_EVT_NUM_COMPLETED_PACKETS        0x13
 struct bt_hci_evt_num_completed_packets {
 	uint8_t  num_handles;
-	struct bt_hci_handle_count h[0];
+	struct bt_hci_handle_count h[];
 } __packed;
 
 #define BT_HCI_EVT_PIN_CODE_REQ                 0x16
@@ -1510,11 +1510,11 @@ struct bt_hci_evt_le_advertising_info {
 	uint8_t      evt_type;
 	bt_addr_le_t addr;
 	uint8_t      length;
-	uint8_t      data[0];
+	uint8_t      data[];
 } __packed;
 struct bt_hci_evt_le_advertising_report {
 	uint8_t num_reports;
-	struct bt_hci_evt_le_advertising_info adv_info[0];
+	struct bt_hci_evt_le_advertising_info adv_info[];
 } __packed;
 
 #define BT_HCI_EVT_LE_CONN_UPDATE_COMPLETE      0x03
@@ -1593,7 +1593,7 @@ struct bt_hci_evt_le_direct_adv_info {
 } __packed;
 struct bt_hci_evt_le_direct_adv_report {
 	uint8_t num_reports;
-	struct bt_hci_evt_le_direct_adv_info direct_adv_info[0];
+	struct bt_hci_evt_le_direct_adv_info direct_adv_info[];
 } __packed;
 
 #define BT_HCI_EVT_LE_PHY_UPDATE_COMPLETE       0x0c
@@ -1628,11 +1628,11 @@ struct bt_hci_evt_le_ext_advertising_info {
 	uint16_t     interval;
 	bt_addr_le_t direct_addr;
 	uint8_t      length;
-	uint8_t      data[0];
+	uint8_t      data[];
 } __packed;
 struct bt_hci_evt_le_ext_advertising_report {
 	uint8_t num_reports;
-	struct bt_hci_evt_le_ext_advertising_info adv_info[0];
+	struct bt_hci_evt_le_ext_advertising_info adv_info[];
 } __packed;
 
 #define BT_HCI_EVT_LE_PER_ADV_SYNC_ESTABLISHED  0x0e
@@ -1654,7 +1654,7 @@ struct bt_hci_evt_le_per_advertising_report {
 	uint8_t  unused;
 	uint8_t  data_status;
 	uint8_t  length;
-	uint8_t  data[0];
+	uint8_t  data[];
 } __packed;
 
 #define BT_HCI_EVT_LE_PER_ADV_SYNC_LOST         0x10
diff --git a/devices/ble_hci/common-hal/_bleio/hci_include/hci_vs.h b/devices/ble_hci/common-hal/_bleio/hci_include/hci_vs.h
index e4f94b6a83..660691398e 100644
--- a/devices/ble_hci/common-hal/_bleio/hci_include/hci_vs.h
+++ b/devices/ble_hci/common-hal/_bleio/hci_include/hci_vs.h
@@ -104,7 +104,7 @@ struct bt_hci_cp_vs_set_trace_enable {
 #define BT_HCI_OP_VS_READ_BUILD_INFO            BT_OP(BT_OGF_VS, 0x0008)
 struct bt_hci_rp_vs_read_build_info {
 	uint8_t  status;
-	uint8_t  info[0];
+	uint8_t  info[];
 } __packed;
 
 struct bt_hci_vs_static_addr {
@@ -116,7 +116,7 @@ struct bt_hci_vs_static_addr {
 struct bt_hci_rp_vs_read_static_addrs {
 	uint8_t   status;
 	uint8_t   num_addrs;
-	struct bt_hci_vs_static_addr a[0];
+	struct bt_hci_vs_static_addr a[];
 } __packed;
 
 #define BT_HCI_OP_VS_READ_KEY_HIERARCHY_ROOTS   BT_OP(BT_OGF_VS, 0x000a)
@@ -143,7 +143,7 @@ struct bt_hci_vs_cmd {
 struct bt_hci_rp_vs_read_host_stack_cmds {
 	uint8_t   status;
 	uint8_t   num_cmds;
-	struct bt_hci_vs_cmd c[0];
+	struct bt_hci_vs_cmd c[];
 } __packed;
 
 #define BT_HCI_VS_SCAN_REQ_REPORTS_DISABLED     0x00
@@ -189,7 +189,7 @@ struct bt_hci_rp_vs_read_tx_power_level {
 struct bt_hci_rp_vs_read_usb_transport_mode {
 	uint8_t  status;
 	uint8_t  num_supported_modes;
-	uint8_t  supported_mode[0];
+	uint8_t  supported_mode[];
 } __packed;
 
 #define BT_HCI_VS_USB_H2_MODE                  0x00
@@ -210,7 +210,7 @@ struct bt_hci_evt_vs {
 #define BT_HCI_EVT_VS_FATAL_ERROR              0x02
 struct bt_hci_evt_vs_fatal_error {
 	uint64_t pc;
-	uint8_t  err_info[0];
+	uint8_t  err_info[];
 } __packed;
 
 #define BT_HCI_VS_TRACE_LMP_TX                 0x01
@@ -221,7 +221,7 @@ struct bt_hci_evt_vs_fatal_error {
 #define BT_HCI_EVT_VS_TRACE_INFO               0x03
 struct bt_hci_evt_vs_trace_info {
 	uint8_t  type;
-	uint8_t  data[0];
+	uint8_t  data[];
 } __packed;
 
 #define BT_HCI_EVT_VS_SCAN_REQ_RX              0x04
@@ -267,14 +267,14 @@ struct bt_hci_rp_mesh_get_opts {
 #define BT_HCI_OC_MESH_SET_SCAN_FILTER         0x01
 struct bt_hci_mesh_pattern {
 	uint8_t pattern_len;
-	uint8_t pattern[0];
+	uint8_t pattern[];
 } __packed;
 
 struct bt_hci_cp_mesh_set_scan_filter {
 	uint8_t      scan_filter;
 	uint8_t      filter_dup;
 	uint8_t      num_patterns;
-	struct    bt_hci_mesh_pattern patterns[0];
+	struct    bt_hci_mesh_pattern patterns[];
 } __packed;
 struct bt_hci_rp_mesh_set_scan_filter {
 	uint8_t      status;
@@ -365,11 +365,11 @@ struct bt_hci_evt_mesh_scan_report {
 	int8_t         rssi;
 	uint32_t        instant;
 	uint8_t         data_len;
-	uint8_t         data[0];
+	uint8_t         data[];
 } __packed;
 struct bt_hci_evt_mesh_scanning_report {
 	uint8_t num_reports;
-	struct bt_hci_evt_mesh_scan_report reports[0];
+	struct bt_hci_evt_mesh_scan_report reports[];
 } __packed;
 
 #ifdef __cplusplus
diff --git a/devices/ble_hci/common-hal/_bleio/hci_include/l2cap_internal.h b/devices/ble_hci/common-hal/_bleio/hci_include/l2cap_internal.h
index bed311cf3c..a0a2ed056c 100644
--- a/devices/ble_hci/common-hal/_bleio/hci_include/l2cap_internal.h
+++ b/devices/ble_hci/common-hal/_bleio/hci_include/l2cap_internal.h
@@ -45,7 +45,7 @@ struct bt_l2cap_sig_hdr {
 #define BT_L2CAP_CMD_REJECT             0x01
 struct bt_l2cap_cmd_reject {
 	uint16_t reason;
-	uint8_t  data[0];
+	uint8_t  data[];
 } __packed;
 
 struct bt_l2cap_cmd_reject_cid_data {
@@ -88,7 +88,7 @@ struct bt_l2cap_conn_rsp {
 struct bt_l2cap_conf_req {
 	uint16_t dcid;
 	uint16_t flags;
-	uint8_t  data[0];
+	uint8_t  data[];
 } __packed;
 
 #define BT_L2CAP_CONF_RSP               0x05
@@ -96,7 +96,7 @@ struct bt_l2cap_conf_rsp {
 	uint16_t scid;
 	uint16_t flags;
 	uint16_t result;
-	uint8_t  data[0];
+	uint8_t  data[];
 } __packed;
 
 /* Option type used by MTU config request data */
@@ -108,7 +108,7 @@ struct bt_l2cap_conf_rsp {
 struct bt_l2cap_conf_opt {
 	uint8_t type;
 	uint8_t len;
-	uint8_t data[0];
+	uint8_t data[];
 } __packed;
 
 #define BT_L2CAP_DISCONN_REQ            0x06
@@ -139,7 +139,7 @@ struct bt_l2cap_info_req {
 struct bt_l2cap_info_rsp {
 	uint16_t type;
 	uint16_t result;
-	uint8_t  data[0];
+	uint8_t  data[];
 } __packed;
 
 #define BT_L2CAP_CONN_PARAM_REQ         0x12
@@ -201,7 +201,7 @@ struct bt_l2cap_ecred_conn_req {
 	uint16_t mtu;
 	uint16_t mps;
 	uint16_t credits;
-	uint16_t scid[0];
+	uint16_t scid[];
 } __packed;
 
 #define BT_L2CAP_ECRED_CONN_RSP         0x18
@@ -210,14 +210,14 @@ struct bt_l2cap_ecred_conn_rsp {
 	uint16_t mps;
 	uint16_t credits;
 	uint16_t result;
-	uint16_t dcid[0];
+	uint16_t dcid[];
 } __packed;
 
 #define BT_L2CAP_ECRED_RECONF_REQ       0x19
 struct bt_l2cap_ecred_reconf_req {
 	uint16_t mtu;
 	uint16_t mps;
-	uint16_t scid[0];
+	uint16_t scid[];
 } __packed;
 
 #define BT_L2CAP_RECONF_SUCCESS         0x0000
diff --git a/locale/circuitpython.pot b/locale/circuitpython.pot
index 59c15027cc..d71ba29a38 100644
--- a/locale/circuitpython.pot
+++ b/locale/circuitpython.pot
@@ -8,7 +8,7 @@ msgid ""
 msgstr ""
 "Project-Id-Version: PACKAGE VERSION\n"
 "Report-Msgid-Bugs-To: \n"
-"POT-Creation-Date: 2020-12-23 15:00-0800\n"
+"POT-Creation-Date: 2020-12-23 21:58-0500\n"
 "PO-Revision-Date: YEAR-MO-DA HO:MI+ZONE\n"
 "Last-Translator: FULL NAME <EMAIL@ADDRESS>\n"
 "Language-Team: LANGUAGE <LL@li.org>\n"
diff --git a/locale/pt_BR.po b/locale/pt_BR.po
index eb73928502..8d3d54fabc 100644
--- a/locale/pt_BR.po
+++ b/locale/pt_BR.po
@@ -6,7 +6,7 @@ msgstr ""
 "Project-Id-Version: PACKAGE VERSION\n"
 "Report-Msgid-Bugs-To: \n"
 "POT-Creation-Date: 2020-12-14 12:59-0500\n"
-"PO-Revision-Date: 2020-12-11 19:08+0000\n"
+"PO-Revision-Date: 2020-12-16 17:00+0000\n"
 "Last-Translator: Wellington Terumi Uemura <wellingtonuemura@gmail.com>\n"
 "Language-Team: \n"
 "Language: pt_BR\n"
@@ -1107,7 +1107,7 @@ msgstr "Frequência PWM inválida"
 
 #: ports/esp32s2/common-hal/analogio/AnalogIn.c
 msgid "Invalid Pin"
-msgstr ""
+msgstr "Pino inválido"
 
 #: py/moduerrno.c shared-module/rgbmatrix/RGBMatrix.c
 msgid "Invalid argument"
@@ -1977,7 +1977,7 @@ msgstr "Não é possível gravar no nvm."
 
 #: shared-bindings/alarm/SleepMemory.c
 msgid "Unable to write to sleep_memory."
-msgstr ""
+msgstr "Não foi possível escrever no sleep_memory."
 
 #: ports/nrf/common-hal/_bleio/UUID.c
 msgid "Unexpected nrfx uuid type"
diff --git a/ports/atmel-samd/Makefile b/ports/atmel-samd/Makefile
index dc7b4e4c89..58c1c0d60e 100644
--- a/ports/atmel-samd/Makefile
+++ b/ports/atmel-samd/Makefile
@@ -94,21 +94,21 @@ endif
 
 ifeq ($(CHIP_FAMILY), samd51)
 PERIPHERALS_CHIP_FAMILY=sam_d5x_e5x
-OPTIMIZATION_FLAGS ?= -O2
+OPTIMIZATION_FLAGS ?= -O2 -fno-inline-functions
 # TinyUSB defines
 CFLAGS += -DCFG_TUSB_MCU=OPT_MCU_SAMD51 -DCFG_TUD_MIDI_RX_BUFSIZE=128 -DCFG_TUD_CDC_RX_BUFSIZE=256 -DCFG_TUD_MIDI_TX_BUFSIZE=128 -DCFG_TUD_CDC_TX_BUFSIZE=256 -DCFG_TUD_MSC_BUFSIZE=1024
 endif
 
 ifeq ($(CHIP_FAMILY), same51)
 PERIPHERALS_CHIP_FAMILY=sam_d5x_e5x
-OPTIMIZATION_FLAGS ?= -O2
+OPTIMIZATION_FLAGS ?= -O2 -fno-inline-functions
 # TinyUSB defines
 CFLAGS += -DCFG_TUSB_MCU=OPT_MCU_SAME5X -DCFG_TUD_MIDI_RX_BUFSIZE=128 -DCFG_TUD_CDC_RX_BUFSIZE=256 -DCFG_TUD_MIDI_TX_BUFSIZE=128 -DCFG_TUD_CDC_TX_BUFSIZE=256 -DCFG_TUD_MSC_BUFSIZE=1024
 endif
 
 ifeq ($(CHIP_FAMILY), same54)
 PERIPHERALS_CHIP_FAMILY=sam_d5x_e5x
-OPTIMIZATION_FLAGS ?= -O2
+OPTIMIZATION_FLAGS ?= -O2 -fno-inline-functions
 # TinyUSB defines
 CFLAGS += -DCFG_TUSB_MCU=OPT_MCU_SAME5X -DCFG_TUD_MIDI_RX_BUFSIZE=128 -DCFG_TUD_CDC_RX_BUFSIZE=256 -DCFG_TUD_MIDI_TX_BUFSIZE=128 -DCFG_TUD_CDC_TX_BUFSIZE=256 -DCFG_TUD_MSC_BUFSIZE=1024
 endif
@@ -116,6 +116,9 @@ endif
 # option to override default optimization level, set in boards/$(BOARD)/mpconfigboard.mk
 CFLAGS += $(OPTIMIZATION_FLAGS)
 
+# Add -ftree-vrp optimization and checking to all builds. It's not enabled for -Os by default.
+CFLAGS += -ftree-vrp
+
 $(echo PERIPHERALS_CHIP_FAMILY=$(PERIPHERALS_CHIP_FAMILY))
 #Debugging/Optimization
 ifeq ($(DEBUG), 1)
diff --git a/ports/atmel-samd/boards/bast_pro_mini_m0/mpconfigboard.mk b/ports/atmel-samd/boards/bast_pro_mini_m0/mpconfigboard.mk
index 055e6b19e2..6a2c896197 100644
--- a/ports/atmel-samd/boards/bast_pro_mini_m0/mpconfigboard.mk
+++ b/ports/atmel-samd/boards/bast_pro_mini_m0/mpconfigboard.mk
@@ -9,3 +9,5 @@ CHIP_FAMILY = samd21
 INTERNAL_FLASH_FILESYSTEM = 1
 LONGINT_IMPL = NONE
 CIRCUITPY_FULL_BUILD = 0
+
+SUPEROPT_GC = 0
diff --git a/ports/atmel-samd/boards/sparkfun_lumidrive/mpconfigboard.mk b/ports/atmel-samd/boards/sparkfun_lumidrive/mpconfigboard.mk
index 3f75d175c8..e71bb07395 100755
--- a/ports/atmel-samd/boards/sparkfun_lumidrive/mpconfigboard.mk
+++ b/ports/atmel-samd/boards/sparkfun_lumidrive/mpconfigboard.mk
@@ -16,3 +16,5 @@ CIRCUITPY_AUDIOBUSIO = 0
 CIRCUITPY_VECTORIO = 0
 
 FROZEN_MPY_DIRS += $(TOP)/frozen/Adafruit_CircuitPython_DotStar
+
+SUPEROPT_GC = 0
diff --git a/ports/atmel-samd/boards/stackrduino_m0_pro/board.c b/ports/atmel-samd/boards/stackrduino_m0_pro/board.c
new file mode 100644
index 0000000000..84960e73cf
--- /dev/null
+++ b/ports/atmel-samd/boards/stackrduino_m0_pro/board.c
@@ -0,0 +1,37 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Scott Shawcroft for Adafruit Industries
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "supervisor/board.h"
+
+void board_init(void) {
+}
+
+bool board_requests_safe_mode(void) {
+    return false;
+}
+
+void reset_board(void) {
+}
diff --git a/ports/atmel-samd/boards/stackrduino_m0_pro/mpconfigboard.h b/ports/atmel-samd/boards/stackrduino_m0_pro/mpconfigboard.h
new file mode 100644
index 0000000000..f0b2764a49
--- /dev/null
+++ b/ports/atmel-samd/boards/stackrduino_m0_pro/mpconfigboard.h
@@ -0,0 +1,33 @@
+#define MICROPY_HW_BOARD_NAME "StackRduino M0 PRO"
+#define MICROPY_HW_MCU_NAME "samd21g18"
+
+#define MICROPY_HW_LED_STATUS   (&pin_PA17)
+#define MICROPY_HW_NEOPIXEL (&pin_PA06)
+
+#define SPI_FLASH_BAUDRATE  (8000000)
+
+#define SPI_FLASH_MOSI_PIN          &pin_PB22
+#define SPI_FLASH_MISO_PIN          &pin_PB03
+#define SPI_FLASH_SCK_PIN           &pin_PB23
+#define SPI_FLASH_CS_PIN            &pin_PA27
+
+// These are pins not to reset.
+#define MICROPY_PORT_A        (PORT_PA06)
+#define MICROPY_PORT_B        (0)
+#define MICROPY_PORT_C        (0)
+
+#define BOARD_HAS_CRYSTAL 1
+
+#define DEFAULT_I2C_BUS_SCL (&pin_PA23)
+#define DEFAULT_I2C_BUS_SDA (&pin_PA22)
+
+#define DEFAULT_SPI_BUS_SCK (&pin_PB11)
+#define DEFAULT_SPI_BUS_MOSI (&pin_PB10)
+#define DEFAULT_SPI_BUS_MISO (&pin_PA12)
+
+#define DEFAULT_UART_BUS_RX (&pin_PA11)
+#define DEFAULT_UART_BUS_TX (&pin_PA10)
+
+// USB is always used internally so skip the pin objects for it.
+#define IGNORE_PIN_PA24     1
+#define IGNORE_PIN_PA25     1
diff --git a/ports/atmel-samd/boards/stackrduino_m0_pro/mpconfigboard.mk b/ports/atmel-samd/boards/stackrduino_m0_pro/mpconfigboard.mk
new file mode 100644
index 0000000000..704d265141
--- /dev/null
+++ b/ports/atmel-samd/boards/stackrduino_m0_pro/mpconfigboard.mk
@@ -0,0 +1,58 @@
+USB_VID = 0x1209
+USB_PID = 0xE3E3
+USB_PRODUCT = "StackRduino M0 PRO"
+USB_MANUFACTURER = "StackRduino"
+
+CHIP_VARIANT = SAMD21G18A
+CHIP_FAMILY = samd21
+
+SPI_FLASH_FILESYSTEM = 1
+EXTERNAL_FLASH_DEVICE_COUNT = 1
+EXTERNAL_FLASH_DEVICES = "W25Q64JV_IQ"
+LONGINT_IMPL = MPZ
+
+
+CIRCUITPY_BITBANGIO = 0
+CIRCUITPY_FREQUENCYIO = 0
+CIRCUITPY_COUNTIO = 0
+CIRCUITPY_I2CPERIPHERAL = 0
+CIRCUITPY_VECTORIO = 0
+CIRCUITPY_BUSDEVICE = 0
+
+CFLAGS_INLINE_LIMIT = 55
+SUPEROPT_GC = 0
+
+CFLAGS_BOARD = --param max-inline-insns-auto=15
+ifeq ($(TRANSLATION), ja)
+RELEASE_NEEDS_CLEAN_BUILD = 1
+CFLAGS_INLINE_LIMIT = 35
+endif
+ifeq ($(TRANSLATION), zh_Latn_pinyin)
+RELEASE_NEEDS_CLEAN_BUILD = 1
+CFLAGS_INLINE_LIMIT = 35
+endif
+ifeq ($(TRANSLATION), de_DE)
+RELEASE_NEEDS_CLEAN_BUILD = 1
+CFLAGS_INLINE_LIMIT = 35
+SUPEROPT_VM = 0
+endif
+ifeq ($(TRANSLATION), pl)
+RELEASE_NEEDS_CLEAN_BUILD = 1
+CFLAGS_INLINE_LIMIT = 35
+SUPEROPT_VM = 0
+endif
+ifeq ($(TRANSLATION), fr)
+RELEASE_NEEDS_CLEAN_BUILD = 1
+CFLAGS_INLINE_LIMIT = 35
+SUPEROPT_VM = 0
+endif
+ifeq ($(TRANSLATION), pt_BR)
+RELEASE_NEEDS_CLEAN_BUILD = 1
+CFLAGS_INLINE_LIMIT = 35
+SUPEROPT_VM = 0
+endif
+ifeq ($(TRANSLATION), es)
+RELEASE_NEEDS_CLEAN_BUILD = 1
+CFLAGS_INLINE_LIMIT = 35
+SUPEROPT_VM = 0
+endif
diff --git a/ports/atmel-samd/boards/stackrduino_m0_pro/pins.c b/ports/atmel-samd/boards/stackrduino_m0_pro/pins.c
new file mode 100644
index 0000000000..95d2eb5a3d
--- /dev/null
+++ b/ports/atmel-samd/boards/stackrduino_m0_pro/pins.c
@@ -0,0 +1,40 @@
+#include "shared-bindings/board/__init__.h"
+
+STATIC const mp_rom_map_elem_t board_global_dict_table[] = {
+    { MP_ROM_QSTR(MP_QSTR_A0), MP_ROM_PTR(&pin_PA02) },
+    { MP_ROM_QSTR(MP_QSTR_A1), MP_ROM_PTR(&pin_PB08) },
+    { MP_ROM_QSTR(MP_QSTR_A2), MP_ROM_PTR(&pin_PB09) },
+    { MP_ROM_QSTR(MP_QSTR_A3), MP_ROM_PTR(&pin_PA04) },
+    { MP_ROM_QSTR(MP_QSTR_A4), MP_ROM_PTR(&pin_PA05) },
+    { MP_ROM_QSTR(MP_QSTR_A5), MP_ROM_PTR(&pin_PB02) },
+    { MP_ROM_QSTR(MP_QSTR_SCK), MP_ROM_PTR(&pin_PB11) },
+    { MP_ROM_QSTR(MP_QSTR_MOSI), MP_ROM_PTR(&pin_PB10) },
+    { MP_ROM_QSTR(MP_QSTR_MISO), MP_ROM_PTR(&pin_PA12) },
+    { MP_ROM_QSTR(MP_QSTR_D0), MP_ROM_PTR(&pin_PA11) },
+    { MP_ROM_QSTR(MP_QSTR_RX), MP_ROM_PTR(&pin_PA11) },
+    { MP_ROM_QSTR(MP_QSTR_D1), MP_ROM_PTR(&pin_PA10) },
+    { MP_ROM_QSTR(MP_QSTR_TX), MP_ROM_PTR(&pin_PA10) },
+    { MP_ROM_QSTR(MP_QSTR_SDA), MP_ROM_PTR(&pin_PA22) },
+    { MP_ROM_QSTR(MP_QSTR_SCL), MP_ROM_PTR(&pin_PA23) },
+    { MP_ROM_QSTR(MP_QSTR_D2), MP_ROM_PTR(&pin_PA08) },
+    { MP_ROM_QSTR(MP_QSTR_D3), MP_ROM_PTR(&pin_PA09) },
+    { MP_ROM_QSTR(MP_QSTR_D4), MP_ROM_PTR(&pin_PA14) },
+    { MP_ROM_QSTR(MP_QSTR_D5), MP_ROM_PTR(&pin_PA15) },
+    { MP_ROM_QSTR(MP_QSTR_D6), MP_ROM_PTR(&pin_PA20) },
+    { MP_ROM_QSTR(MP_QSTR_D7), MP_ROM_PTR(&pin_PA21) },
+    { MP_ROM_QSTR(MP_QSTR_D8), MP_ROM_PTR(&pin_PA06) },
+	{ MP_ROM_QSTR(MP_QSTR_NEOPIXEL), MP_ROM_PTR(&pin_PA06) },
+    { MP_ROM_QSTR(MP_QSTR_D9), MP_ROM_PTR(&pin_PA07) },
+    { MP_ROM_QSTR(MP_QSTR_D10), MP_ROM_PTR(&pin_PA18) },
+    { MP_ROM_QSTR(MP_QSTR_D11), MP_ROM_PTR(&pin_PA16) },
+    { MP_ROM_QSTR(MP_QSTR_D12), MP_ROM_PTR(&pin_PA19) },
+    { MP_ROM_QSTR(MP_QSTR_D13), MP_ROM_PTR(&pin_PA17) },
+	{ MP_ROM_QSTR(MP_QSTR_D14), MP_ROM_PTR(&pin_PA28) },
+	{ MP_ROM_QSTR(MP_QSTR_BUTTON), MP_ROM_PTR(&pin_PA28) },
+	{ MP_ROM_QSTR(MP_QSTR_D15), MP_ROM_PTR(&pin_PA13) },
+	{ MP_ROM_QSTR(MP_QSTR_CHRG_EN), MP_ROM_PTR(&pin_PA13) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
+    { MP_ROM_QSTR(MP_QSTR_SPI), MP_ROM_PTR(&board_spi_obj) },
+    { MP_ROM_QSTR(MP_QSTR_UART), MP_ROM_PTR(&board_uart_obj) },
+};
+MP_DEFINE_CONST_DICT(board_module_globals, board_global_dict_table);
diff --git a/ports/atmel-samd/common-hal/frequencyio/FrequencyIn.c b/ports/atmel-samd/common-hal/frequencyio/FrequencyIn.c
index 02d0482dca..f973db90b0 100644
--- a/ports/atmel-samd/common-hal/frequencyio/FrequencyIn.c
+++ b/ports/atmel-samd/common-hal/frequencyio/FrequencyIn.c
@@ -82,7 +82,8 @@ void frequencyin_emergency_cancel_capture(uint8_t index) {
     #ifdef SAM_D5X_E5X
     NVIC_EnableIRQ(EIC_0_IRQn + self->channel);
     #endif
-    mp_raise_RuntimeError(translate("Frequency captured is above capability. Capture Paused."));
+    // Frequency captured is above capability. Capture paused.
+    // We can't raise an error here; we're in an interrupt handler.
 }
 
 void frequencyin_interrupt_handler(uint8_t index) {
diff --git a/ports/cxd56/Makefile b/ports/cxd56/Makefile
index 5201f0db56..1c48a23ca5 100644
--- a/ports/cxd56/Makefile
+++ b/ports/cxd56/Makefile
@@ -122,7 +122,7 @@ CFLAGS += \
 	-fdata-sections \
 	-Wall \
 
-OPTIMIZATION_FLAGS ?= -O2
+OPTIMIZATION_FLAGS ?= -O2 -fno-inline-functions
 
 # option to override compiler optimization level, set in boards/$(BOARD)/mpconfigboard.mk
 CFLAGS += $(OPTIMIZATION_FLAGS)
diff --git a/ports/esp32s2/Makefile b/ports/esp32s2/Makefile
index e496a61a46..e08b8a7928 100644
--- a/ports/esp32s2/Makefile
+++ b/ports/esp32s2/Makefile
@@ -106,6 +106,8 @@ INC += -isystem esp-idf/components/heap/include
 INC += -isystem esp-idf/components/esp_system/include
 INC += -isystem esp-idf/components/spi_flash/include
 INC += -isystem esp-idf/components/nvs_flash/include
+INC += -isystem esp-idf/components/app_update/include
+INC += -isystem esp-idf/components/bootloader_support/include
 INC += -I$(BUILD)/esp-idf/config
 
 CFLAGS += -DHAVE_CONFIG_H \
@@ -334,10 +336,10 @@ $(BUILD)/firmware.uf2: $(BUILD)/circuitpython-firmware.bin
 	$(Q)$(PYTHON3) $(TOP)/tools/uf2/utils/uf2conv.py -f 0xbfdd4eee -b 0x0000 -c -o $@ $^
 
 flash: $(BUILD)/firmware.bin
-	esptool.py --chip esp32s2 -p $(PORT) --no-stub -b 460800 --before=default_reset --after=no_reset write_flash $(FLASH_FLAGS) 0x0000 $^
+	esptool.py --chip esp32s2 -p $(PORT) -b 460800 --before=default_reset --after=no_reset write_flash $(FLASH_FLAGS) 0x0000 $^
 
 flash-circuitpython-only: $(BUILD)/circuitpython-firmware.bin
-	esptool.py --chip esp32s2 -p $(PORT) --no-stub -b 460800 --before=default_reset --after=no_reset write_flash $(FLASH_FLAGS) 0x10000 $^
+	esptool.py --chip esp32s2 -p $(PORT) -b 460800 --before=default_reset --after=no_reset write_flash $(FLASH_FLAGS) 0x10000 $^
 
 include $(TOP)/py/mkrules.mk
 
diff --git a/ports/esp32s2/boards/adafruit_magtag_2.9_grayscale/mpconfigboard.h b/ports/esp32s2/boards/adafruit_magtag_2.9_grayscale/mpconfigboard.h
index be376e5a94..8dfe912712 100644
--- a/ports/esp32s2/boards/adafruit_magtag_2.9_grayscale/mpconfigboard.h
+++ b/ports/esp32s2/boards/adafruit_magtag_2.9_grayscale/mpconfigboard.h
@@ -26,7 +26,7 @@
 
 //Micropython setup
 
-#define MICROPY_HW_BOARD_NAME       "MagTag"
+#define MICROPY_HW_BOARD_NAME       "Adafruit MagTag"
 #define MICROPY_HW_MCU_NAME         "ESP32S2"
 
 #define MICROPY_HW_NEOPIXEL (&pin_GPIO1)
diff --git a/ports/esp32s2/boards/adafruit_metro_esp32s2/mpconfigboard.h b/ports/esp32s2/boards/adafruit_metro_esp32s2/mpconfigboard.h
index 7280aab9c2..b25d7d1169 100644
--- a/ports/esp32s2/boards/adafruit_metro_esp32s2/mpconfigboard.h
+++ b/ports/esp32s2/boards/adafruit_metro_esp32s2/mpconfigboard.h
@@ -26,7 +26,7 @@
 
 //Micropython setup
 
-#define MICROPY_HW_BOARD_NAME       "Metro ESP32S2"
+#define MICROPY_HW_BOARD_NAME       "Adafruit Metro ESP32S2"
 #define MICROPY_HW_MCU_NAME         "ESP32S2"
 
 #define MICROPY_HW_NEOPIXEL (&pin_GPIO45)
diff --git a/ports/esp32s2/common-hal/dualbank/__init__.c b/ports/esp32s2/common-hal/dualbank/__init__.c
new file mode 100644
index 0000000000..0f468a036b
--- /dev/null
+++ b/ports/esp32s2/common-hal/dualbank/__init__.c
@@ -0,0 +1,139 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2020 microDev
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "common-hal/dualbank/__init__.h"
+#include "shared-bindings/dualbank/__init__.h"
+
+#include <string.h>
+
+#include "esp_log.h"
+#include "esp_ota_ops.h"
+
+static const esp_partition_t *update_partition = NULL;
+static esp_ota_handle_t update_handle = 0;
+
+static const char *TAG = "dualbank";
+
+void dualbank_reset(void) {
+    // should use `abort` instead of `end`
+    // but not in idf v4.2
+    // esp_ota_abort(update_handle);
+    if (esp_ota_end(update_handle) == ESP_OK) {
+        update_handle = 0;
+        update_partition = NULL;
+    }
+}
+
+static void __attribute__((noreturn)) task_fatal_error(void) {
+    ESP_LOGE(TAG, "Exiting task due to fatal error...");
+    mp_raise_RuntimeError(translate("Update Failed"));
+}
+
+void common_hal_dualbank_flash(const void *buf, const size_t len, const size_t offset) {
+    esp_err_t err;
+
+    const esp_partition_t *running = esp_ota_get_running_partition();
+    const esp_partition_t *last_invalid = esp_ota_get_last_invalid_partition();
+
+    if (update_partition == NULL) {
+        update_partition = esp_ota_get_next_update_partition(NULL);
+
+        ESP_LOGI(TAG, "Running partition type %d subtype %d (offset 0x%08x)",
+                running->type, running->subtype, running->address);
+
+        ESP_LOGI(TAG, "Writing partition type %d subtype %d (offset 0x%08x)\n",
+                update_partition->type, update_partition->subtype, update_partition->address);
+
+        assert(update_partition != NULL);
+    }
+
+    if (update_handle == 0) {
+        if (len > sizeof(esp_image_header_t) + sizeof(esp_image_segment_header_t) + sizeof(esp_app_desc_t)) {
+            esp_app_desc_t new_app_info;
+            memcpy(&new_app_info, &((char *)buf)[sizeof(esp_image_header_t) + sizeof(esp_image_segment_header_t)], sizeof(esp_app_desc_t));
+            ESP_LOGI(TAG, "New firmware version: %s", new_app_info.version);
+
+            esp_app_desc_t running_app_info;
+            if (esp_ota_get_partition_description(running, &running_app_info) == ESP_OK) {
+                ESP_LOGI(TAG, "Running firmware version: %s", running_app_info.version);
+            }
+
+            esp_app_desc_t invalid_app_info;
+            if (esp_ota_get_partition_description(last_invalid, &invalid_app_info) == ESP_OK) {
+                ESP_LOGI(TAG, "Last invalid firmware version: %s", invalid_app_info.version);
+            }
+
+            // check new version with running version
+            if (memcmp(new_app_info.version, running_app_info.version, sizeof(new_app_info.version)) == 0) {
+                ESP_LOGW(TAG, "New version is the same as running version.");
+                task_fatal_error();
+            }
+
+            // check new version with last invalid partition
+            if (last_invalid != NULL) {
+                if (memcmp(new_app_info.version, invalid_app_info.version, sizeof(new_app_info.version)) == 0) {
+                    ESP_LOGW(TAG, "New version is the same as invalid version.");
+                    task_fatal_error();
+                }
+            }
+
+            err = esp_ota_begin(update_partition, OTA_WITH_SEQUENTIAL_WRITES, &update_handle);
+            if (err != ESP_OK) {
+                ESP_LOGE(TAG, "esp_ota_begin failed (%s)", esp_err_to_name(err));
+                task_fatal_error();
+            }
+        } else {
+            ESP_LOGE(TAG, "received package is not fit len");
+            task_fatal_error();
+        }
+    }
+
+    if (offset == 0) {
+        err = esp_ota_write(update_handle, buf, len);
+    } else {
+        err = esp_ota_write_with_offset(update_handle, buf, len, offset);
+    }
+    if (err != ESP_OK) {
+        ESP_LOGE(TAG, "esp_ota_write failed (%s)", esp_err_to_name(err));
+        task_fatal_error();
+    }
+}
+
+void common_hal_dualbank_switch(void) {
+    if (esp_ota_end(update_handle) == ESP_OK) {
+        update_handle = 0;
+        update_partition = NULL;
+    }
+    esp_err_t err = esp_ota_set_boot_partition(esp_ota_get_next_update_partition(NULL));
+    if (err != ESP_OK) {
+        if (err == ESP_ERR_OTA_VALIDATE_FAILED) {
+            ESP_LOGE(TAG, "Image validation failed, image is corrupted");
+            mp_raise_RuntimeError(translate("Firmware image is invalid"));
+        }
+        ESP_LOGE(TAG, "esp_ota_set_boot_partition failed (%s)!", esp_err_to_name(err));
+        task_fatal_error();
+    }
+}
diff --git a/ports/esp32s2/common-hal/dualbank/__init__.h b/ports/esp32s2/common-hal/dualbank/__init__.h
new file mode 100644
index 0000000000..8b18336c94
--- /dev/null
+++ b/ports/esp32s2/common-hal/dualbank/__init__.h
@@ -0,0 +1,32 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2020 microDev
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef MICROPY_INCLUDED_ESP32S2_COMMON_HAL_DUALBANK___INIT___H
+#define MICROPY_INCLUDED_ESP32S2_COMMON_HAL_DUALBANK___INIT___H
+
+extern void dualbank_reset(void);
+
+#endif //MICROPY_INCLUDED_ESP32S2_COMMON_HAL_DUALBANK___INIT___H
diff --git a/ports/esp32s2/mpconfigport.mk b/ports/esp32s2/mpconfigport.mk
index b3b2a6d700..2ad8afb51c 100644
--- a/ports/esp32s2/mpconfigport.mk
+++ b/ports/esp32s2/mpconfigport.mk
@@ -19,6 +19,7 @@ CIRCUITPY_AUDIOBUSIO = 0
 CIRCUITPY_AUDIOIO = 0
 CIRCUITPY_CANIO = 1
 CIRCUITPY_COUNTIO = 1
+CIRCUITPY_DUALBANK = 1
 CIRCUITPY_FREQUENCYIO = 1
 CIRCUITPY_I2CPERIPHERAL = 0
 CIRCUITPY_ROTARYIO = 1
diff --git a/ports/esp32s2/supervisor/port.c b/ports/esp32s2/supervisor/port.c
index 17a413a2ed..ff35845f71 100644
--- a/ports/esp32s2/supervisor/port.c
+++ b/ports/esp32s2/supervisor/port.c
@@ -41,6 +41,7 @@
 #include "common-hal/busio/I2C.h"
 #include "common-hal/busio/SPI.h"
 #include "common-hal/busio/UART.h"
+#include "common-hal/dualbank/__init__.h"
 #include "common-hal/ps2io/Ps2.h"
 #include "common-hal/pulseio/PulseIn.h"
 #include "common-hal/pwmio/PWMOut.h"
@@ -144,6 +145,10 @@ void reset_port(void) {
     analogout_reset();
 #endif
 
+#if CIRCUITPY_DUALBANK
+    dualbank_reset();
+#endif
+
 #if CIRCUITPY_PS2IO
     ps2_reset();
 #endif
diff --git a/ports/litex/Makefile b/ports/litex/Makefile
index 612953daaf..f384f24577 100644
--- a/ports/litex/Makefile
+++ b/ports/litex/Makefile
@@ -80,7 +80,7 @@ ifeq ($(DEBUG), 1)
   OPTIMIZATION_FLAGS ?= -Og
 else
   CFLAGS += -DNDEBUG -ggdb3
-  OPTIMIZATION_FLAGS ?= -O2
+  OPTIMIZATION_FLAGS ?= -O2 -fno-inline-functions
   # TODO: Test with -flto
   ### CFLAGS += -flto
 endif
diff --git a/ports/mimxrt10xx/Makefile b/ports/mimxrt10xx/Makefile
index a17e5f7030..04949bf01c 100644
--- a/ports/mimxrt10xx/Makefile
+++ b/ports/mimxrt10xx/Makefile
@@ -75,7 +75,7 @@ INC += \
 
 # NDEBUG disables assert() statements. This reduces code size pretty dramatically, per tannewt.
 
-CFLAGS += -Os -DNDEBUG -ffreestanding
+CFLAGS += -Os -ftree-vrp -DNDEBUG -ffreestanding
 
 # TinyUSB defines
 CFLAGS += -DCFG_TUSB_MCU=OPT_MCU_MIMXRT10XX -DCFG_TUD_MIDI_RX_BUFSIZE=512 -DCFG_TUD_CDC_RX_BUFSIZE=512 -DCFG_TUD_MIDI_TX_BUFSIZE=512 -DCFG_TUD_CDC_TX_BUFSIZE=512 -DCFG_TUD_MSC_BUFSIZE=1024
@@ -108,7 +108,7 @@ CFLAGS += \
 	-g3 -Wno-unused-parameter \
 	-ffunction-sections -fdata-sections -fstack-usage
 
-OPTIMIZATION_FLAGS ?= -O2
+OPTIMIZATION_FLAGS ?= -O2 -fno-inline-functions
 
 # option to override compiler optimization level, set in boards/$(BOARD)/mpconfigboard.mk
 CFLAGS += $(OPTIMIZATION_FLAGS)
diff --git a/ports/mimxrt10xx/boards/feather_m7_1011/mpconfigboard.h b/ports/mimxrt10xx/boards/feather_m7_1011/mpconfigboard.h
index e96ec13dd9..e027e2b5ee 100644
--- a/ports/mimxrt10xx/boards/feather_m7_1011/mpconfigboard.h
+++ b/ports/mimxrt10xx/boards/feather_m7_1011/mpconfigboard.h
@@ -1,4 +1,4 @@
-#define MICROPY_HW_BOARD_NAME "Feather MIMXRT1011"
+#define MICROPY_HW_BOARD_NAME "Adafruit Feather MIMXRT1011"
 #define MICROPY_HW_MCU_NAME "IMXRT1011DAE5A"
 
 #define MICROPY_HW_NEOPIXEL (&pin_GPIO_00)
diff --git a/ports/nrf/Makefile b/ports/nrf/Makefile
index 3fef68e88e..278625e92d 100755
--- a/ports/nrf/Makefile
+++ b/ports/nrf/Makefile
@@ -89,7 +89,7 @@ ifeq ($(DEBUG), 1)
   CFLAGS += -ggdb3
   OPTIMIZATION_FLAGS = -Og
 else
-  OPTIMIZATION_FLAGS ?= -O2
+  OPTIMIZATION_FLAGS ?= -O2 -fno-inline-functions
   CFLAGS += -DNDEBUG -ggdb3
   CFLAGS += -flto -flto-partition=none
 endif
diff --git a/ports/nrf/boards/bastble/README.md b/ports/nrf/boards/bastble/README.md
new file mode 100644
index 0000000000..0af6209bdb
--- /dev/null
+++ b/ports/nrf/boards/bastble/README.md
@@ -0,0 +1,4 @@
+# Electronic Cats BastBLE
+
+The [BastBLE](https://electroniccats.com/store/bast-ble/) based on Nordic nRF 52840 and containing
+a powerful Cortex M4F. This board include a external memory QSPI flash.
diff --git a/ports/nrf/boards/bastble/board.c b/ports/nrf/boards/bastble/board.c
new file mode 100644
index 0000000000..b6fb04f06c
--- /dev/null
+++ b/ports/nrf/boards/bastble/board.c
@@ -0,0 +1,41 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2017 Scott Shawcroft for Adafruit Industries
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "supervisor/board.h"
+#include "nrf.h"
+#include "nrf_rtc.h"
+
+void board_init(void) {
+
+}
+
+bool board_requests_safe_mode(void) {
+  return false;
+}
+
+void reset_board(void) {
+
+}
diff --git a/ports/nrf/boards/bastble/mpconfigboard.h b/ports/nrf/boards/bastble/mpconfigboard.h
new file mode 100644
index 0000000000..e36227c6bc
--- /dev/null
+++ b/ports/nrf/boards/bastble/mpconfigboard.h
@@ -0,0 +1,25 @@
+#include "nrfx/hal/nrf_gpio.h"
+
+#define MICROPY_HW_BOARD_NAME       "BastBLE"
+#define MICROPY_HW_MCU_NAME         "nRF52840"
+
+#define CIRCUITPY_AUTORELOAD_DELAY_MS 500
+
+#if QSPI_FLASH_FILESYSTEM
+#define MICROPY_QSPI_DATA0                NRF_GPIO_PIN_MAP(0, 30)
+#define MICROPY_QSPI_DATA1                NRF_GPIO_PIN_MAP(0, 29)
+#define MICROPY_QSPI_DATA2                NRF_GPIO_PIN_MAP(0, 28)
+#define MICROPY_QSPI_DATA3                NRF_GPIO_PIN_MAP(0, 2)
+#define MICROPY_QSPI_SCK                  NRF_GPIO_PIN_MAP(0, 3)
+#define MICROPY_QSPI_CS                   NRF_GPIO_PIN_MAP(0, 26)
+#endif
+
+#define DEFAULT_I2C_BUS_SCL         (&pin_P1_10)
+#define DEFAULT_I2C_BUS_SDA         (&pin_P1_11)
+
+#define DEFAULT_SPI_BUS_SCK         (&pin_P1_00)
+#define DEFAULT_SPI_BUS_MOSI        (&pin_P1_06)
+#define DEFAULT_SPI_BUS_MISO        (&pin_P0_15)
+
+#define DEFAULT_UART_BUS_RX         (&pin_P0_09)
+#define DEFAULT_UART_BUS_TX         (&pin_P0_10)
diff --git a/ports/nrf/boards/bastble/mpconfigboard.mk b/ports/nrf/boards/bastble/mpconfigboard.mk
new file mode 100644
index 0000000000..eca900de77
--- /dev/null
+++ b/ports/nrf/boards/bastble/mpconfigboard.mk
@@ -0,0 +1,10 @@
+USB_VID = 0x1209
+USB_PID = 0x805A
+USB_PRODUCT = "BastBLE"
+USB_MANUFACTURER = "ElectronicCats"
+
+MCU_CHIP = nrf52840
+
+QSPI_FLASH_FILESYSTEM = 1
+EXTERNAL_FLASH_DEVICE_COUNT = 1
+EXTERNAL_FLASH_DEVICES = "GD25Q16C"
diff --git a/ports/nrf/boards/bastble/pins.c b/ports/nrf/boards/bastble/pins.c
new file mode 100644
index 0000000000..b35dad43de
--- /dev/null
+++ b/ports/nrf/boards/bastble/pins.c
@@ -0,0 +1,47 @@
+#include "shared-bindings/board/__init__.h"
+
+STATIC const mp_rom_map_elem_t board_module_globals_table[] = {
+    { MP_ROM_QSTR(MP_QSTR_D2), MP_ROM_PTR(&pin_P1_11) },
+    { MP_ROM_QSTR(MP_QSTR_D3), MP_ROM_PTR(&pin_P1_10) },
+    { MP_ROM_QSTR(MP_QSTR_D4), MP_ROM_PTR(&pin_P1_00) },
+    { MP_ROM_QSTR(MP_QSTR_D5), MP_ROM_PTR(&pin_P1_02) },
+    { MP_ROM_QSTR(MP_QSTR_D6), MP_ROM_PTR(&pin_P1_13) },
+    { MP_ROM_QSTR(MP_QSTR_D7), MP_ROM_PTR(&pin_P1_06) },
+    { MP_ROM_QSTR(MP_QSTR_D8), MP_ROM_PTR(&pin_P0_15) },
+    { MP_ROM_QSTR(MP_QSTR_D9), MP_ROM_PTR(&pin_P0_06) },
+    { MP_ROM_QSTR(MP_QSTR_D10), MP_ROM_PTR(&pin_P1_09) },
+    { MP_ROM_QSTR(MP_QSTR_D11), MP_ROM_PTR(&pin_P0_08) },
+    { MP_ROM_QSTR(MP_QSTR_D12), MP_ROM_PTR(&pin_P0_26) },
+    { MP_ROM_QSTR(MP_QSTR_D13), MP_ROM_PTR(&pin_P0_07) },
+
+    { MP_ROM_QSTR(MP_QSTR_A0), MP_ROM_PTR(&pin_P0_02) },
+    { MP_ROM_QSTR(MP_QSTR_A1), MP_ROM_PTR(&pin_P0_28) },
+    { MP_ROM_QSTR(MP_QSTR_A2), MP_ROM_PTR(&pin_P0_05) },
+    { MP_ROM_QSTR(MP_QSTR_A3), MP_ROM_PTR(&pin_P0_03) },
+
+    { MP_ROM_QSTR(MP_QSTR_A4), MP_ROM_PTR(&pin_P0_30) },
+    { MP_ROM_QSTR(MP_QSTR_SDA), MP_ROM_PTR(&pin_P1_11) },
+
+    { MP_ROM_QSTR(MP_QSTR_A5), MP_ROM_PTR(&pin_P0_29) },
+    { MP_ROM_QSTR(MP_QSTR_SCL), MP_ROM_PTR(&pin_P1_10) },
+
+    { MP_ROM_QSTR(MP_QSTR_MOSI), MP_ROM_PTR(&pin_P1_06) },
+    { MP_ROM_QSTR(MP_QSTR_MISO), MP_ROM_PTR(&pin_P0_15) },
+
+    { MP_ROM_QSTR(MP_QSTR_SCK), MP_ROM_PTR(&pin_P1_00) },
+    { MP_ROM_QSTR(MP_QSTR_LED), MP_ROM_PTR(&pin_P0_24)  },
+
+    { MP_ROM_QSTR(MP_QSTR_AREF), MP_ROM_PTR(&pin_P0_31) },
+
+    // voltage sense battery
+    { MP_ROM_QSTR(MP_QSTR_VBAT), MP_ROM_PTR(&pin_P0_26)  },
+
+    { MP_ROM_QSTR(MP_QSTR_TX), MP_ROM_PTR(&pin_P0_10) },
+    { MP_ROM_QSTR(MP_QSTR_RX), MP_ROM_PTR(&pin_P0_09) },
+
+    { MP_ROM_QSTR(MP_QSTR_UART), MP_ROM_PTR(&board_uart_obj) },
+    { MP_ROM_QSTR(MP_QSTR_SPI), MP_ROM_PTR(&board_spi_obj) },
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
+};
+
+MP_DEFINE_CONST_DICT(board_module_globals, board_module_globals_table);
diff --git a/ports/nrf/boards/simmel/mpconfigboard.mk b/ports/nrf/boards/simmel/mpconfigboard.mk
index 704881b3c4..dd6b1fbfdf 100644
--- a/ports/nrf/boards/simmel/mpconfigboard.mk
+++ b/ports/nrf/boards/simmel/mpconfigboard.mk
@@ -16,12 +16,14 @@ CIRCUITPY_AUDIOMP3 = 0
 CIRCUITPY_BUSIO = 1
 CIRCUITPY_DISPLAYIO = 0
 CIRCUITPY_FRAMEBUFFERIO = 0
+CIRCUITPY_GAMEPAD = 0
 CIRCUITPY_NEOPIXEL_WRITE = 0
 CIRCUITPY_NVM = 0
 CIRCUITPY_PIXELBUF  = 0
 CIRCUITPY_RGBMATRIX = 0
 CIRCUITPY_ROTARYIO = 0
 CIRCUITPY_RTC = 1
+CIRCUITPY_SDCARDIO = 0
 CIRCUITPY_TOUCHIO = 0
 CIRCUITPY_ULAB = 0
 CIRCUITPY_WATCHDOG = 1
diff --git a/ports/nrf/common-hal/_bleio/Adapter.c b/ports/nrf/common-hal/_bleio/Adapter.c
index 537f43f237..53a40f9a67 100644
--- a/ports/nrf/common-hal/_bleio/Adapter.c
+++ b/ports/nrf/common-hal/_bleio/Adapter.c
@@ -470,7 +470,16 @@ mp_obj_t common_hal_bleio_adapter_start_scan(bleio_adapter_obj_t *self, uint8_t*
     ble_drv_add_event_handler(scan_on_ble_evt, self->scan_results);
 
     uint32_t nrf_timeout = SEC_TO_UNITS(timeout, UNIT_10_MS);
-    if (timeout <= 0.0001) {
+    if (nrf_timeout > UINT16_MAX) {
+        // 0xffff / 100
+        mp_raise_ValueError(translate("timeout must be < 655.35 secs"));
+    }
+    if (nrf_timeout == 0 && timeout > 0.0f) {
+        // Make sure converted timeout is > 0 if original timeout is > 0.
+        mp_raise_ValueError(translate("non-zero timeout must be > 0.01"));
+    }
+
+    if (nrf_timeout) {
         nrf_timeout = BLE_GAP_SCAN_TIMEOUT_UNLIMITED;
     }
 
diff --git a/ports/stm/Makefile b/ports/stm/Makefile
index b9426e07ec..e09fe736cc 100755
--- a/ports/stm/Makefile
+++ b/ports/stm/Makefile
@@ -86,7 +86,7 @@ ifeq ($(DEBUG), 1)
 	CFLAGS += -fno-inline -fno-ipa-sra
 else
 	CFLAGS += -DNDEBUG
-	OPTIMIZATION_FLAGS ?= -O2
+	OPTIMIZATION_FLAGS ?= -O2 -fno-inline-functions
 	CFLAGS += -ggdb3
 	# TODO: Test with -flto
 	# CFLAGS += -flto
@@ -95,6 +95,9 @@ endif
 # to override compiler optimization level, set in boards/$(BOARD)/mpconfigboard.mk
 CFLAGS += $(OPTIMIZATION_FLAGS)
 
+# Add -ftree-vrp optimization and checking to all builds. It's not enabled for -Os by default.
+CFLAGS += -ftree-vrp
+
 # MCU Series is defined by the HAL package and doesn't need to be specified here
 C_DEFS = -D$(MCU_PACKAGE) -DUSE_HAL_DRIVER -DUSE_FULL_LL_DRIVER -D$(MCU_VARIANT)
 
diff --git a/ports/stm/boards/espruino_pico/mpconfigboard.mk b/ports/stm/boards/espruino_pico/mpconfigboard.mk
index 556ff35c45..14f9323fde 100644
--- a/ports/stm/boards/espruino_pico/mpconfigboard.mk
+++ b/ports/stm/boards/espruino_pico/mpconfigboard.mk
@@ -20,3 +20,5 @@ LD_FILE = boards/STM32F401xd_fs.ld
 # lto for this port, and if other stuff hasn't been added in the
 # meantime
 CIRCUITPY_ULAB = 0
+
+SUPEROPT_GC = 0
diff --git a/ports/stm/boards/feather_stm32f405_express/mpconfigboard.h b/ports/stm/boards/feather_stm32f405_express/mpconfigboard.h
index 0d49748c84..e69be6cf95 100644
--- a/ports/stm/boards/feather_stm32f405_express/mpconfigboard.h
+++ b/ports/stm/boards/feather_stm32f405_express/mpconfigboard.h
@@ -26,7 +26,7 @@
 
 //Micropython setup
 
-#define MICROPY_HW_BOARD_NAME       "Feather STM32F405 Express"
+#define MICROPY_HW_BOARD_NAME       "Adafruit Feather STM32F405 Express"
 #define MICROPY_HW_MCU_NAME         "STM32F405RG"
 
 #define FLASH_SIZE                  (0x100000)
diff --git a/ports/stm/boards/stm32f411ce_blackpill/mpconfigboard.h b/ports/stm/boards/stm32f411ce_blackpill/mpconfigboard.h
index 83a8bded39..4351339540 100644
--- a/ports/stm/boards/stm32f411ce_blackpill/mpconfigboard.h
+++ b/ports/stm/boards/stm32f411ce_blackpill/mpconfigboard.h
@@ -42,6 +42,9 @@
 // #define SPI_FLASH_SCK_PIN           (&pin_PA05)
 // #define SPI_FLASH_CS_PIN            (&pin_PA04)
 
+#define DEFAULT_I2C_BUS_SCL (&pin_PB06)
+#define DEFAULT_I2C_BUS_SDA (&pin_PB07)
+
 #define CIRCUITPY_AUTORELOAD_DELAY_MS (500)
 
 #define BOARD_FLASH_SIZE (FLASH_SIZE - 0x2000 - 0xC000)
diff --git a/ports/stm/boards/stm32f411ce_blackpill/pins.c b/ports/stm/boards/stm32f411ce_blackpill/pins.c
index 2f8aab6e8e..16946b8bee 100644
--- a/ports/stm/boards/stm32f411ce_blackpill/pins.c
+++ b/ports/stm/boards/stm32f411ce_blackpill/pins.c
@@ -35,5 +35,10 @@ STATIC const mp_rom_map_elem_t board_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_C14), MP_ROM_PTR(&pin_PC14) },
     { MP_ROM_QSTR(MP_QSTR_C13), MP_ROM_PTR(&pin_PC13) },
     { MP_ROM_QSTR(MP_QSTR_LED), MP_ROM_PTR(&pin_PC13) },
+
+    { MP_ROM_QSTR(MP_QSTR_SDA), MP_ROM_PTR(&pin_PB07) },
+    { MP_ROM_QSTR(MP_QSTR_SCL), MP_ROM_PTR(&pin_PB06) },
+
+    { MP_ROM_QSTR(MP_QSTR_I2C), MP_ROM_PTR(&board_i2c_obj) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_module_globals_table);
diff --git a/py/circuitpy_defns.mk b/py/circuitpy_defns.mk
index 1eafce2595..94f8ba42e7 100644
--- a/py/circuitpy_defns.mk
+++ b/py/circuitpy_defns.mk
@@ -205,6 +205,9 @@ endif
 ifeq ($(CIRCUITPY_OS),1)
 SRC_PATTERNS += os/%
 endif
+ifeq ($(CIRCUITPY_DUALBANK),1)
+SRC_PATTERNS += dualbank/%
+endif
 ifeq ($(CIRCUITPY_PIXELBUF),1)
 SRC_PATTERNS += _pixelbuf/%
 endif
@@ -348,6 +351,7 @@ SRC_COMMON_HAL_ALL = \
 	nvm/ByteArray.c \
 	nvm/__init__.c \
 	os/__init__.c \
+	dualbank/__init__.c \
 	ps2io/Ps2.c \
 	ps2io/__init__.c \
 	pulseio/PulseIn.c \
diff --git a/py/circuitpy_mpconfig.h b/py/circuitpy_mpconfig.h
index 0bd889ccdf..08c92a77ef 100644
--- a/py/circuitpy_mpconfig.h
+++ b/py/circuitpy_mpconfig.h
@@ -539,6 +539,13 @@ extern const struct _mp_obj_module_t os_module;
 #define OS_MODULE_ALT_NAME
 #endif
 
+#if CIRCUITPY_DUALBANK
+extern const struct _mp_obj_module_t dualbank_module;
+#define DUALBANK_MODULE           { MP_OBJ_NEW_QSTR(MP_QSTR_dualbank), (mp_obj_t)&dualbank_module },
+#else
+#define DUALBANK_MODULE
+#endif
+
 #if CIRCUITPY_PEW
 extern const struct _mp_obj_module_t pew_module;
 #define PEW_MODULE          { MP_OBJ_NEW_QSTR(MP_QSTR__pew),(mp_obj_t)&pew_module },
@@ -827,6 +834,7 @@ extern const struct _mp_obj_module_t wifi_module;
     NETWORK_MODULE \
       SOCKET_MODULE \
       WIZNET_MODULE \
+    DUALBANK_MODULE \
     PEW_MODULE \
     PIXELBUF_MODULE \
     PS2IO_MODULE \
diff --git a/py/circuitpy_mpconfig.mk b/py/circuitpy_mpconfig.mk
index 370f133739..e588c41e0d 100644
--- a/py/circuitpy_mpconfig.mk
+++ b/py/circuitpy_mpconfig.mk
@@ -96,7 +96,7 @@ CFLAGS += -DCIRCUITPY_BLEIO=$(CIRCUITPY_BLEIO)
 CIRCUITPY_BOARD ?= 1
 CFLAGS += -DCIRCUITPY_BOARD=$(CIRCUITPY_BOARD)
 
-CIRCUITPY_BUSDEVICE ?= $(CIRCUITPY_FULL_BUILD)
+CIRCUITPY_BUSDEVICE = 0
 CFLAGS += -DCIRCUITPY_BUSDEVICE=$(CIRCUITPY_BUSDEVICE)
 
 CIRCUITPY_BUILTINS_POW3 ?= $(CIRCUITPY_FULL_BUILD)
@@ -179,6 +179,9 @@ CFLAGS += -DCIRCUITPY_NVM=$(CIRCUITPY_NVM)
 CIRCUITPY_OS ?= 1
 CFLAGS += -DCIRCUITPY_OS=$(CIRCUITPY_OS)
 
+CIRCUITPY_DUALBANK ?= 0
+CFLAGS += -DCIRCUITPY_DUALBANK=$(CIRCUITPY_DUALBANK)
+
 CIRCUITPY_PIXELBUF ?= $(CIRCUITPY_FULL_BUILD)
 CFLAGS += -DCIRCUITPY_PIXELBUF=$(CIRCUITPY_PIXELBUF)
 
diff --git a/py/py.mk b/py/py.mk
index 1a8f1219a5..3f94aa67a0 100644
--- a/py/py.mk
+++ b/py/py.mk
@@ -19,7 +19,7 @@ endif
 QSTR_GLOBAL_DEPENDENCIES += $(PY_SRC)/mpconfig.h mpconfigport.h
 
 # some code is performance bottleneck and compiled with other optimization options
-_CSUPEROPT = -O3
+CSUPEROPT = -O3
 
 # this sets the config file for FatFs
 CFLAGS_MOD += -DFFCONF_H=\"lib/oofatfs/ffconf.h\"
diff --git a/shared-bindings/_bleio/Adapter.c b/shared-bindings/_bleio/Adapter.c
index 682177093d..7d7076aab6 100644
--- a/shared-bindings/_bleio/Adapter.c
+++ b/shared-bindings/_bleio/Adapter.c
@@ -33,8 +33,8 @@
 #include "shared-bindings/_bleio/Address.h"
 #include "shared-bindings/_bleio/Adapter.h"
 
-#define ADV_INTERVAL_MIN (0.0020f)
-#define ADV_INTERVAL_MIN_STRING "0.0020"
+#define ADV_INTERVAL_MIN (0.02001f)
+#define ADV_INTERVAL_MIN_STRING "0.02001"
 #define ADV_INTERVAL_MAX (10.24f)
 #define ADV_INTERVAL_MAX_STRING "10.24"
 // 20ms is recommended by Apple
@@ -307,7 +307,7 @@ STATIC mp_obj_t bleio_adapter_start_scan(size_t n_args, const mp_obj_t *pos_args
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
 
-    mp_float_t timeout = 0;
+    mp_float_t timeout = 0.0f;
     if (args[ARG_timeout].u_obj != mp_const_none) {
         timeout = mp_obj_get_float(args[ARG_timeout].u_obj);
     }
@@ -325,6 +325,13 @@ STATIC mp_obj_t bleio_adapter_start_scan(size_t n_args, const mp_obj_t *pos_args
         mp_raise_ValueError_varg(translate("interval must be in range %s-%s"), INTERVAL_MIN_STRING, INTERVAL_MAX_STRING);
     }
 
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wfloat-equal"
+    if (timeout != 0.0f && timeout < interval) {
+        mp_raise_ValueError(translate("non-zero timeout must be >= interval"));
+    }
+#pragma GCC diagnostic pop
+
     const mp_float_t window = mp_obj_float_get(args[ARG_window].u_obj);
     if (window > interval) {
         mp_raise_ValueError(translate("window must be <= interval"));
diff --git a/shared-bindings/_bleio/Characteristic.c b/shared-bindings/_bleio/Characteristic.c
index 5e384a44ca..a0751b7e34 100644
--- a/shared-bindings/_bleio/Characteristic.c
+++ b/shared-bindings/_bleio/Characteristic.c
@@ -110,8 +110,8 @@ STATIC mp_obj_t bleio_characteristic_add_to_service(size_t n_args, const mp_obj_
     common_hal_bleio_attribute_security_mode_check_valid(write_perm);
 
     const mp_int_t max_length_int = args[ARG_max_length].u_int;
-    if (max_length_int <= 0) {
-        mp_raise_ValueError(translate("max_length must be > 0"));
+    if (max_length_int < 0) {
+        mp_raise_ValueError(translate("max_length must be >= 0"));
     }
     const size_t max_length = (size_t) max_length_int;
     const bool fixed_length =  args[ARG_fixed_length].u_bool;
diff --git a/shared-bindings/_bleio/Descriptor.c b/shared-bindings/_bleio/Descriptor.c
index c313007c6d..60f0acf44b 100644
--- a/shared-bindings/_bleio/Descriptor.c
+++ b/shared-bindings/_bleio/Descriptor.c
@@ -101,8 +101,8 @@ STATIC mp_obj_t bleio_descriptor_add_to_characteristic(size_t n_args, const mp_o
     common_hal_bleio_attribute_security_mode_check_valid(write_perm);
 
     const mp_int_t max_length_int = args[ARG_max_length].u_int;
-    if (max_length_int <= 0) {
-        mp_raise_ValueError(translate("max_length must be > 0"));
+    if (max_length_int < 0) {
+        mp_raise_ValueError(translate("max_length must be >= 0"));
     }
     const size_t max_length = (size_t) max_length_int;
     const bool fixed_length =  args[ARG_fixed_length].u_bool;
diff --git a/shared-bindings/adafruit_bus_device/I2CDevice.c b/shared-bindings/adafruit_bus_device/I2CDevice.c
index 4c9086162d..a4c04e198c 100644
--- a/shared-bindings/adafruit_bus_device/I2CDevice.c
+++ b/shared-bindings/adafruit_bus_device/I2CDevice.c
@@ -163,7 +163,7 @@ STATIC MP_DEFINE_CONST_FUN_OBJ_KW(adafruit_bus_device_i2cdevice_readinto_obj, 2,
 //|         """
 //|         ...
 //|
-STATIC void write(adafruit_bus_device_i2cdevice_obj_t *self, mp_obj_t buffer, int32_t start, mp_int_t end) {
+STATIC void write(adafruit_bus_device_i2cdevice_obj_t *self, mp_obj_t buffer, int32_t start, mp_int_t end, bool transmit_stop_bit) {
     mp_buffer_info_t bufinfo;
     mp_get_buffer_raise(buffer, &bufinfo, MP_BUFFER_READ);
 
@@ -173,7 +173,7 @@ STATIC void write(adafruit_bus_device_i2cdevice_obj_t *self, mp_obj_t buffer, in
         mp_raise_ValueError(translate("Buffer must be at least length 1"));
     }
 
-    uint8_t status = common_hal_adafruit_bus_device_i2cdevice_write(MP_OBJ_TO_PTR(self), ((uint8_t*)bufinfo.buf) + start, length);
+    uint8_t status = common_hal_adafruit_bus_device_i2cdevice_write(MP_OBJ_TO_PTR(self), ((uint8_t*)bufinfo.buf) + start, length, transmit_stop_bit);
     if (status != 0) {
         mp_raise_OSError(status);
     }
@@ -191,7 +191,7 @@ STATIC mp_obj_t adafruit_bus_device_i2cdevice_write(size_t n_args, const mp_obj_
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
 
-    write(self, args[ARG_buffer].u_obj, args[ARG_start].u_int, args[ARG_end].u_int);
+    write(self, args[ARG_buffer].u_obj, args[ARG_start].u_int, args[ARG_end].u_int, true);
     return mp_const_none;
 }
 MP_DEFINE_CONST_FUN_OBJ_KW(adafruit_bus_device_i2cdevice_write_obj, 2, adafruit_bus_device_i2cdevice_write);
@@ -233,7 +233,7 @@ STATIC mp_obj_t adafruit_bus_device_i2cdevice_write_then_readinto(size_t n_args,
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args - 1, pos_args + 1, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
 
-    write(self, args[ARG_out_buffer].u_obj, args[ARG_out_start].u_int, args[ARG_out_end].u_int);
+    write(self, args[ARG_out_buffer].u_obj, args[ARG_out_start].u_int, args[ARG_out_end].u_int, false);
 
     readinto(self, args[ARG_in_buffer].u_obj, args[ARG_in_start].u_int, args[ARG_in_end].u_int);
 
diff --git a/shared-bindings/adafruit_bus_device/I2CDevice.h b/shared-bindings/adafruit_bus_device/I2CDevice.h
index 7b2182ff03..cf7b1321a0 100644
--- a/shared-bindings/adafruit_bus_device/I2CDevice.h
+++ b/shared-bindings/adafruit_bus_device/I2CDevice.h
@@ -45,7 +45,7 @@ extern const mp_obj_type_t adafruit_bus_device_i2cdevice_type;
 // Initializes the hardware peripheral.
 extern void common_hal_adafruit_bus_device_i2cdevice_construct(adafruit_bus_device_i2cdevice_obj_t *self, busio_i2c_obj_t *i2c, uint8_t device_address);
 extern uint8_t common_hal_adafruit_bus_device_i2cdevice_readinto(adafruit_bus_device_i2cdevice_obj_t *self, mp_obj_t buffer, size_t length);
-extern uint8_t common_hal_adafruit_bus_device_i2cdevice_write(adafruit_bus_device_i2cdevice_obj_t *self, mp_obj_t buffer, size_t length);
+extern uint8_t common_hal_adafruit_bus_device_i2cdevice_write(adafruit_bus_device_i2cdevice_obj_t *self, mp_obj_t buffer, size_t length, bool transmit_stop_bit);
 extern void common_hal_adafruit_bus_device_i2cdevice_lock(adafruit_bus_device_i2cdevice_obj_t *self);
 extern void common_hal_adafruit_bus_device_i2cdevice_unlock(adafruit_bus_device_i2cdevice_obj_t *self);
 extern void common_hal_adafruit_bus_device_i2cdevice_probe_for_device(adafruit_bus_device_i2cdevice_obj_t *self);
diff --git a/shared-bindings/camera/ImageFormat.c b/shared-bindings/camera/ImageFormat.c
index d4bdddc562..9f2f9617f6 100644
--- a/shared-bindings/camera/ImageFormat.c
+++ b/shared-bindings/camera/ImageFormat.c
@@ -38,7 +38,6 @@
 //|     RGB565: ImageFormat
 //|     """RGB565 format."""
 //|
-const mp_obj_type_t camera_imageformat_type;
 
 const camera_imageformat_obj_t camera_imageformat_jpg_obj = {
     { &camera_imageformat_type },
diff --git a/shared-bindings/camera/ImageFormat.h b/shared-bindings/camera/ImageFormat.h
index 8abc88438d..32a36354fc 100644
--- a/shared-bindings/camera/ImageFormat.h
+++ b/shared-bindings/camera/ImageFormat.h
@@ -35,7 +35,7 @@ typedef enum {
     IMAGEFORMAT_RGB565,
 } camera_imageformat_t;
 
-const mp_obj_type_t camera_imageformat_type;
+extern const mp_obj_type_t camera_imageformat_type;
 
 camera_imageformat_t camera_imageformat_obj_to_type(mp_obj_t obj);
 mp_obj_t camera_imageformat_type_to_obj(camera_imageformat_t mode);
diff --git a/shared-bindings/dualbank/__init__.c b/shared-bindings/dualbank/__init__.c
new file mode 100644
index 0000000000..8021ab18b9
--- /dev/null
+++ b/shared-bindings/dualbank/__init__.c
@@ -0,0 +1,115 @@
+/*
+ * This file is part of the Micro Python project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2020 microDev
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "shared-bindings/dualbank/__init__.h"
+
+//| """DUALBANK Module
+//|
+//| The `dualbank` module adds ability to update and switch
+//| between the two app partitions.
+//|
+//| There are two identical partitions, these contain different
+//| firmware versions.
+//| Having two partitions enables rollback functionality.
+//|
+//| The two partitions are defined as boot partition and
+//| next-update partition. Calling `dualbank.flash()` writes
+//| the next-update partition.
+//|
+//| After the next-update partition is written a validation
+//| check is performed and on a successful validation this
+//| partition is set as the boot partition. On next reset,
+//| firmware will be loaded from this partition.
+//|
+//| Here is the sequence of commands to follow:
+//|
+//| .. code-block:: python
+//|
+//|     import dualbank
+//|
+//|     dualbank.flash(buffer, offset)
+//|     dualbank.switch()
+//| """
+//| ...
+//|
+
+//| def flash(*buffer: ReadableBuffer, offset: int=0) -> None:
+//|     """Writes one of two app partitions at the given offset.
+//|
+//|     This can be called multiple times when flashing the firmware
+//|     in small chunks.
+//|     """
+//|     ...
+//|
+STATIC mp_obj_t dualbank_flash(size_t n_args, const mp_obj_t *pos_args, mp_map_t *kw_args) {
+    enum { ARG_buffer, ARG_offset };
+    static const mp_arg_t allowed_args[] = {
+        { MP_QSTR_buffer, MP_ARG_OBJ | MP_ARG_REQUIRED },
+        { MP_QSTR_offset, MP_ARG_INT | MP_ARG_KW_ONLY, {.u_int = 0} },
+    };
+
+    mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
+    mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
+
+    if (args[ARG_offset].u_int < 0) {
+        mp_raise_ValueError(translate("offset must be >= 0"));
+    }
+
+    mp_buffer_info_t bufinfo;
+    mp_get_buffer_raise(args[ARG_buffer].u_obj, &bufinfo, MP_BUFFER_READ);
+
+    common_hal_dualbank_flash(bufinfo.buf, bufinfo.len, args[ARG_offset].u_int);
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_KW(dualbank_flash_obj, 0, dualbank_flash);
+
+//| def switch() -> None:
+//|     """Switches the boot partition.
+//|
+//|     On next reset, firmware will be loaded from the partition
+//|     just switched over to.
+//|     """
+//|     ...
+//|
+STATIC mp_obj_t dualbank_switch(void) {
+    common_hal_dualbank_switch();
+    return mp_const_none;
+}
+STATIC MP_DEFINE_CONST_FUN_OBJ_0(dualbank_switch_obj, dualbank_switch);
+
+STATIC const mp_rom_map_elem_t dualbank_module_globals_table[] = {
+    // module name
+    { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_dualbank) },
+    // module functions
+    { MP_ROM_QSTR(MP_QSTR_flash), MP_ROM_PTR(&dualbank_flash_obj) },
+    { MP_ROM_QSTR(MP_QSTR_switch), MP_ROM_PTR(&dualbank_switch_obj) },
+};
+STATIC MP_DEFINE_CONST_DICT(dualbank_module_globals, dualbank_module_globals_table);
+
+const mp_obj_module_t dualbank_module = {
+    .base = { &mp_type_module },
+    .globals = (mp_obj_dict_t*)&dualbank_module_globals,
+};
diff --git a/shared-bindings/dualbank/__init__.h b/shared-bindings/dualbank/__init__.h
new file mode 100644
index 0000000000..7edbc6d68a
--- /dev/null
+++ b/shared-bindings/dualbank/__init__.h
@@ -0,0 +1,35 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2020 microDev
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#ifndef MICROPY_INCLUDED_SHARED_BINDINGS_DUALBANK___INIT___H
+#define MICROPY_INCLUDED_SHARED_BINDINGS_DUALBANK___INIT___H
+
+#include "py/runtime.h"
+
+extern void common_hal_dualbank_switch(void);
+extern void common_hal_dualbank_flash(const void *buf, const size_t len, const size_t offset);
+
+#endif  // MICROPY_INCLUDED_SHARED_BINDINGS_DUALBANK___INIT___H
diff --git a/shared-module/adafruit_bus_device/I2CDevice.c b/shared-module/adafruit_bus_device/I2CDevice.c
index ee4b4fa554..83abe80d64 100644
--- a/shared-module/adafruit_bus_device/I2CDevice.c
+++ b/shared-module/adafruit_bus_device/I2CDevice.c
@@ -57,8 +57,8 @@ uint8_t common_hal_adafruit_bus_device_i2cdevice_readinto(adafruit_bus_device_i2
     return common_hal_busio_i2c_read(self->i2c, self->device_address, buffer, length);
 }
 
-uint8_t common_hal_adafruit_bus_device_i2cdevice_write(adafruit_bus_device_i2cdevice_obj_t *self, mp_obj_t buffer, size_t length) {
-    return common_hal_busio_i2c_write(self->i2c, self->device_address, buffer, length, true);
+uint8_t common_hal_adafruit_bus_device_i2cdevice_write(adafruit_bus_device_i2cdevice_obj_t *self, mp_obj_t buffer, size_t length, bool transmit_stop_bit) {
+    return common_hal_busio_i2c_write(self->i2c, self->device_address, buffer, length, transmit_stop_bit);
 }
 
 void common_hal_adafruit_bus_device_i2cdevice_probe_for_device(adafruit_bus_device_i2cdevice_obj_t *self) {
diff --git a/shared-module/displayio/ColorConverter.c b/shared-module/displayio/ColorConverter.c
index 80558d037a..40dcd9d167 100644
--- a/shared-module/displayio/ColorConverter.c
+++ b/shared-module/displayio/ColorConverter.c
@@ -29,6 +29,8 @@
 #include "py/misc.h"
 #include "py/runtime.h"
 
+#define NO_TRANSPARENT_COLOR (0x1000000)
+
 uint32_t displayio_colorconverter_dither_noise_1 (uint32_t n)
 {
   n = (n >> 13) ^ n;
@@ -42,6 +44,7 @@ uint32_t displayio_colorconverter_dither_noise_2(uint32_t x, uint32_t y) {
 
 void common_hal_displayio_colorconverter_construct(displayio_colorconverter_t* self, bool dither) {
     self->dither = dither;
+    self->transparent_color = NO_TRANSPARENT_COLOR;
 }
 
 uint16_t displayio_colorconverter_compute_rgb565(uint32_t color_rgb888) {
@@ -130,7 +133,7 @@ bool common_hal_displayio_colorconverter_get_dither(displayio_colorconverter_t*
 }
 
 void common_hal_displayio_colorconverter_make_transparent(displayio_colorconverter_t* self, uint32_t transparent_color) {
-    if (self->transparent_color >= 0x1000000) {
+    if (self->transparent_color != NO_TRANSPARENT_COLOR) {
         mp_raise_RuntimeError(translate("Only one color can be transparent at a time"));
     }
     self->transparent_color = transparent_color;
@@ -138,8 +141,8 @@ void common_hal_displayio_colorconverter_make_transparent(displayio_colorconvert
 
 void common_hal_displayio_colorconverter_make_opaque(displayio_colorconverter_t* self, uint32_t transparent_color) {
     (void) transparent_color;
-    // 0x1000000 will never equal a valid color
-    self->transparent_color = 0x1000000;
+    // NO_TRANSPARENT_COLOR will never equal a valid color
+    self->transparent_color = NO_TRANSPARENT_COLOR;
 }
 
 void displayio_colorconverter_convert(displayio_colorconverter_t *self, const _displayio_colorspace_t* colorspace, const displayio_input_pixel_t *input_pixel, displayio_output_pixel_t *output_color) {
diff --git a/shared-module/displayio/OnDiskBitmap.c b/shared-module/displayio/OnDiskBitmap.c
index 993fc03de6..c1a0ddeb7e 100644
--- a/shared-module/displayio/OnDiskBitmap.c
+++ b/shared-module/displayio/OnDiskBitmap.c
@@ -57,7 +57,7 @@ void common_hal_displayio_ondiskbitmap_construct(displayio_ondiskbitmap_t *self,
     uint32_t compression = read_word(bmp_header, 15);
     uint32_t number_of_colors = read_word(bmp_header, 23);
 
-    bool indexed = ((bits_per_pixel <= 8) && (number_of_colors != 0));
+    bool indexed = bits_per_pixel <= 8;
     self->bitfield_compressed  = (compression == 3);
     self->bits_per_pixel = bits_per_pixel;
     self->width = read_word(bmp_header, 9);
@@ -75,6 +75,9 @@ void common_hal_displayio_ondiskbitmap_construct(displayio_ondiskbitmap_t *self,
             self->b_bitmask = 0x1f;
         }
     } else if (indexed && self->bits_per_pixel != 1) {
+        if (number_of_colors == 0) {
+            number_of_colors = 1 << bits_per_pixel;
+        }
         uint16_t palette_size = number_of_colors * sizeof(uint32_t);
         uint16_t palette_offset = 0xe + header_size;
 
diff --git a/supervisor/shared/external_flash/devices.h b/supervisor/shared/external_flash/devices.h
index a874dbd4fd..c8c941adf8 100644
--- a/supervisor/shared/external_flash/devices.h
+++ b/supervisor/shared/external_flash/devices.h
@@ -94,6 +94,26 @@ typedef struct {
     .single_status_byte = false, \
 }
 
+// Settings for the Adesto Tech AT25DF641-SSHD-T 8MiB SPI flash
+// for the Oak Dev Tech Icy Tree M0 (SAMD21) feather board.
+// Source: https://www.digikey.com/product-detail/en/adesto-technologies/AT25SF641-SDHD-T/1265-1180-1-ND/
+// Datasheet: https://www.adestotech.com/wp-content/uploads/doc8693.pdf
+#define AT25DF641A {\
+    .total_size = (1 << 23), /* 8 MiB */ \
+    .start_up_time_us = 10000, \
+    .manufacturer_id = 0x1f, \
+    .memory_type = 0x48, \
+    .capacity = 0x00, \
+    .max_clock_speed_mhz = 85, \
+    .quad_enable_bit_mask = 0x00, \
+    .has_sector_protection = true, \
+    .supports_fast_read = true, \
+    .supports_qspi = false, \
+    .supports_qspi_writes = false, \
+    .write_status_register_split = false, \
+    .single_status_byte = false, \
+}
+
 // Settings for the Adesto Tech AT25SF161-SSHD-T 2MiB SPI flash
 // for the StringCar M0 (SAMD21) Express board.
 // Source: https://www.digikey.com/product-detail/en/adesto-technologies/AT25SF161-SDHD-T/1265-1230-1-ND/
@@ -114,6 +134,7 @@ typedef struct {
     .single_status_byte = false, \
 }
 
+
 // Settings for the Adesto Tech AT25SF041 1MiB SPI flash. It's on the SparkFun
 // SAMD51 Thing Plus board
 // Datasheet: https://www.adestotech.com/wp-content/uploads/DS-AT25SF041_044.pdf
@@ -363,6 +384,24 @@ typedef struct {
     .write_status_register_split = false, \
 }
 
+// Settings for the Winbond W25Q64FV 8MiB SPI flash.
+// Datasheet: https://www.winbond.com/resource-files/w25q64fv%20revs%2007182017.pdf
+#define W25Q64FV {\
+    .total_size = (1 << 23), /* 8 MiB */ \
+    .start_up_time_us = 5000, \
+    .manufacturer_id = 0xef, \
+    .memory_type = 0x40, \
+    .capacity = 0x17, \
+    .max_clock_speed_mhz = 104, \
+    .quad_enable_bit_mask = 0x02, \
+    .has_sector_protection = false, \
+    .supports_fast_read = true, \
+    .supports_qspi = true, \
+    .supports_qspi_writes = true, \
+    .write_status_register_split = false, \
+    .single_status_byte = false, \
+}
+
 // Settings for the Winbond W25Q64JV-IM 8MiB SPI flash. Note that JV-IQ has a different .memory_type (0x40)
 // Datasheet: http://www.winbond.com/resource-files/w25q64jv%20revj%2003272018%20plus.pdf
 #define W25Q64JV_IM {\
@@ -537,7 +576,7 @@ typedef struct {
     .start_up_time_us = 800, \
     .manufacturer_id = 0xc2, \
     .memory_type = 0x28, \
-    .capacity = 0x18, \
+    .capacity = 0x15, \
     .max_clock_speed_mhz = 33, /* 8 mhz for dual/quad */ \
     .quad_enable_bit_mask = 0x80, \
     .has_sector_protection = false, \
@@ -566,6 +605,43 @@ typedef struct {
     .single_status_byte = true, \
 }
 
+// Settings for the Macronix MX25L51245G 64MiB SPI flash.
+// Datasheet: https://www.macronix.com/Lists/Datasheet/Attachments/7437/MX25L51245G,%203V,%20512Mb,%20v1.6.pdf
+#define MX25L25645G  {\
+    .total_size = (1 << 25), /* 32 MiB */ \
+    .start_up_time_us = 5000, \
+    .manufacturer_id = 0x9f, \
+    .memory_type = 0xab, \
+    .capacity = 0x90, \
+    .max_clock_speed_mhz = 133, \
+   .quad_enable_bit_mask = 0xaf, \
+    .has_sector_protection = false, \
+    .supports_fast_read = true, \
+    .supports_qspi = true, \
+    .supports_qspi_writes = true, \
+    .write_status_register_split = false, \
+    .single_status_byte = true, \
+}
+
+// Settings for the Macronix MX25L12833F 16MiB SPI flash
+// Datasheet: https://www.macronix.com/Lists/Datasheet/Attachments/7447/MX25L12833F,%203V,%20128Mb,%20v1.0.pdf
+
+#define MX25L12833F {\
+    .total_size = (1UL << 24), /* 16 MiB */ \
+    .start_up_time_us = 5000, \
+    .manufacturer_id = 0xc2, \
+    .memory_type = 0x20, \
+    .capacity = 0x18, \
+    .max_clock_speed_mhz = 133, \
+    .quad_enable_bit_mask = 0x40, \
+    .has_sector_protection = true, \
+    .supports_fast_read = true, \
+    .supports_qspi = true, \
+    .supports_qspi_writes = true, \
+    .write_status_register_split = false, \
+    .single_status_byte = true, \
+  }
+
 // Settings for the Winbond W25Q128JV-PM 16MiB SPI flash. Note that JV-IM has a different .memory_type (0x70)
 // Datasheet: https://www.winbond.com/resource-files/w25q128jv%20revf%2003272018%20plus.pdf
 #define W25Q128JV_PM {\
diff --git a/supervisor/shared/usb/usb_msc_flash.c b/supervisor/shared/usb/usb_msc_flash.c
index b39f60dcd2..7532b6aead 100644
--- a/supervisor/shared/usb/usb_msc_flash.c
+++ b/supervisor/shared/usb/usb_msc_flash.c
@@ -39,7 +39,7 @@
 
 #define MSC_FLASH_BLOCK_SIZE    512
 
-static bool ejected[1] = {false};
+static bool ejected[1] = {true};
 
 void usb_msc_mount(void) {
     // Reset the ejection tracking every time we're plugged into USB. This allows for us to battery