diff --git a/ports/raspberrypi/Makefile b/ports/raspberrypi/Makefile
index 455672d617..55093eaeea 100644
--- a/ports/raspberrypi/Makefile
+++ b/ports/raspberrypi/Makefile
@@ -198,7 +198,7 @@ else
 endif
 
 # Remove -Wno-stringop-overflow after we can test with CI's GCC 10. Mac's looks weird.
-DISABLE_WARNINGS = -Wno-stringop-overflow -Wno-unused-variable -Wno-strict-overflow -Wno-cast-align -Wno-strict-prototypes -Wno-nested-externs -Wno-double-promotion -Wno-sign-compare
+DISABLE_WARNINGS = -Wno-stringop-overflow -Wno-unused-variable -Wno-strict-overflow -Wno-cast-align
 
 CFLAGS += $(INC) -Wall -Werror -std=gnu11 -nostdlib -fshort-enums $(BASE_CFLAGS) $(CFLAGS_MOD) $(COPT) $(DISABLE_WARNINGS) -Werror=missing-prototypes
 
@@ -256,7 +256,7 @@ SRC_SDK := \
 	$(SRC_SDK_CYW43) \
 
 SRC_SDK := $(addprefix sdk/, $(SRC_SDK))
-$(patsubst %.c,$(BUILD)/%.o,$(SRC_SDK) $(SRC_CYW43)): CFLAGS += -Wno-missing-prototypes -Wno-undef -Wno-unused-function
+$(patsubst %.c,$(BUILD)/%.o,$(SRC_SDK) $(SRC_CYW43)): CFLAGS += -Wno-missing-prototypes -Wno-undef -Wno-unused-function -Wno-nested-externs -Wno-strict-prototypes -Wno-double-promotion -Wno-sign-compare
 
 SRC_C += \
 	boards/$(BOARD)/board.c \
diff --git a/ports/raspberrypi/common-hal/busio/I2C.c b/ports/raspberrypi/common-hal/busio/I2C.c
index 6b15bee512..c68499591c 100644
--- a/ports/raspberrypi/common-hal/busio/I2C.c
+++ b/ports/raspberrypi/common-hal/busio/I2C.c
@@ -190,7 +190,7 @@ STATIC uint8_t _common_hal_busio_i2c_write(busio_i2c_obj_t *self, uint16_t addr,
         return status;
     }
 
-    int result = i2c_write_timeout_us(self->peripheral, addr, data, len, !transmit_stop_bit, BUS_TIMEOUT_US);
+    size_t result = i2c_write_timeout_us(self->peripheral, addr, data, len, !transmit_stop_bit, BUS_TIMEOUT_US);
     if (result == len) {
         return 0;
     }
@@ -211,7 +211,7 @@ uint8_t common_hal_busio_i2c_write(busio_i2c_obj_t *self, uint16_t addr,
 
 uint8_t common_hal_busio_i2c_read(busio_i2c_obj_t *self, uint16_t addr,
     uint8_t *data, size_t len) {
-    int result = i2c_read_timeout_us(self->peripheral, addr, data, len, false, BUS_TIMEOUT_US);
+    size_t result = i2c_read_timeout_us(self->peripheral, addr, data, len, false, BUS_TIMEOUT_US);
     if (result == len) {
         return 0;
     }
diff --git a/ports/raspberrypi/common-hal/rp2pio/StateMachine.c b/ports/raspberrypi/common-hal/rp2pio/StateMachine.c
index 78703351d7..d24e9b2b7c 100644
--- a/ports/raspberrypi/common-hal/rp2pio/StateMachine.c
+++ b/ports/raspberrypi/common-hal/rp2pio/StateMachine.c
@@ -71,7 +71,7 @@ STATIC void *_interrupt_arg[NUM_PIOS][NUM_PIO_STATE_MACHINES];
 STATIC void rp2pio_statemachine_interrupt_handler(void);
 
 static void rp2pio_statemachine_set_pull(uint32_t pull_pin_up, uint32_t pull_pin_down, uint32_t pins_we_use) {
-    for (int i = 0; i < TOTAL_GPIO_COUNT; i++) {
+    for (size_t i = 0; i < TOTAL_GPIO_COUNT; i++) {
         bool used = pins_we_use & (1 << i);
         if (used) {
             bool pull_up = pull_pin_up & (1 << i);
@@ -231,7 +231,7 @@ bool rp2pio_statemachine_construct(rp2pio_statemachine_obj_t *self,
         program_offset = 32;
     }
 
-    int state_machine = -1;
+    size_t state_machine = NUM_PIO_STATE_MACHINES;
     if (pio_index < NUM_PIOS) {
         PIO pio = pio_instances[pio_index];
         for (size_t i = 0; i < NUM_PIOS; i++) {
diff --git a/ports/raspberrypi/common-hal/rp2pio/__init__.c b/ports/raspberrypi/common-hal/rp2pio/__init__.c
index 8b8101fbe5..61a77e021c 100644
--- a/ports/raspberrypi/common-hal/rp2pio/__init__.c
+++ b/ports/raspberrypi/common-hal/rp2pio/__init__.c
@@ -33,7 +33,7 @@ bool common_hal_rp2pio_pins_are_sequential(size_t len, mp_obj_t *items) {
         return true;
     }
     const mcu_pin_obj_t *last_pin = validate_obj_is_pin(items[0]);
-    for (int i = 1; i < len; i++) {
+    for (size_t i = 1; i < len; i++) {
         const mcu_pin_obj_t *pin = validate_obj_is_pin(items[i]);
         if (pin->number != last_pin->number + 1) {
             return false;
diff --git a/ports/raspberrypi/common-hal/socketpool/Socket.c b/ports/raspberrypi/common-hal/socketpool/Socket.c
index fb777a3f04..6ea2dc2c3c 100644
--- a/ports/raspberrypi/common-hal/socketpool/Socket.c
+++ b/ports/raspberrypi/common-hal/socketpool/Socket.c
@@ -409,7 +409,7 @@ STATIC mp_uint_t lwip_raw_udp_receive(socketpool_socket_obj_t *socket, byte *buf
         // Wait for data to arrive on UDP socket.
         mp_uint_t start = mp_hal_ticks_ms();
         while (socket->incoming.pbuf == NULL) {
-            if (socket->timeout != -1 && mp_hal_ticks_ms() - start > socket->timeout) {
+            if (socket->timeout != (unsigned)-1 && mp_hal_ticks_ms() - start > socket->timeout) {
                 *_errno = MP_ETIMEDOUT;
                 return -1;
             }
@@ -479,7 +479,7 @@ STATIC mp_uint_t lwip_tcp_send(socketpool_socket_obj_t *socket, const byte *buf,
         // Avoid sending too small packets, so wait until at least 16 bytes available
         while (socket->state >= STATE_CONNECTED && (available = tcp_sndbuf(socket->pcb.tcp)) < 16) {
             MICROPY_PY_LWIP_EXIT
-            if (socket->timeout != -1 && mp_hal_ticks_ms() - start > socket->timeout) {
+            if (socket->timeout != (unsigned)-1 && mp_hal_ticks_ms() - start > socket->timeout) {
                 *_errno = MP_ETIMEDOUT;
                 return MP_STREAM_ERROR;
             }
@@ -546,7 +546,7 @@ STATIC mp_uint_t lwip_tcp_receive(socketpool_socket_obj_t *socket, byte *buf, mp
 
         mp_uint_t start = mp_hal_ticks_ms();
         while (socket->state == STATE_CONNECTED && socket->incoming.pbuf == NULL) {
-            if (socket->timeout != -1 && mp_hal_ticks_ms() - start > socket->timeout) {
+            if (socket->timeout != (unsigned)-1 && mp_hal_ticks_ms() - start > socket->timeout) {
                 *_errno = MP_ETIMEDOUT;
                 return -1;
             }
@@ -778,7 +778,7 @@ socketpool_socket_obj_t *common_hal_socketpool_socket_accept(socketpool_socket_o
             MICROPY_PY_LWIP_EXIT
             m_del_obj(socketpool_socket_obj_t, socket2);
             mp_raise_OSError(MP_EAGAIN);
-        } else if (socket->timeout != -1) {
+        } else if (socket->timeout != (unsigned)-1) {
             mp_uint_t retries = socket->timeout / 100;
             while (*incoming_connection == NULL) {
                 MICROPY_PY_LWIP_EXIT
@@ -952,7 +952,7 @@ void common_hal_socketpool_socket_connect(socketpool_socket_obj_t *socket,
             MICROPY_PY_LWIP_EXIT
 
             // And now we wait...
-            if (socket->timeout != -1) {
+            if (socket->timeout != (unsigned)-1) {
                 for (mp_uint_t retries = socket->timeout / 100; retries--;) {
                     mp_hal_delay_ms(100);
                     if (socket->state != STATE_CONNECTING) {
@@ -1048,7 +1048,7 @@ mp_uint_t common_hal_socketpool_socket_recvfrom_into(socketpool_socket_obj_t *so
             ret = lwip_raw_udp_receive(socket, (byte *)buf, len, ip, port, &_errno);
             break;
     }
-    if (ret == -1) {
+    if (ret == (unsigned)-1) {
         mp_raise_OSError(_errno);
     }
 
@@ -1097,7 +1097,7 @@ int socketpool_socket_send(socketpool_socket_obj_t *socket, const uint8_t *buf,
             ret = lwip_raw_udp_send(socket, buf, len, NULL, 0, &_errno);
             break;
     }
-    if (ret == -1) {
+    if (ret == (unsigned)-1) {
         return -_errno;
     }
     return ret;
@@ -1134,7 +1134,7 @@ mp_uint_t common_hal_socketpool_socket_sendto(socketpool_socket_obj_t *socket,
             ret = lwip_raw_udp_send(socket, buf, len, &ip, port, &_errno);
             break;
     }
-    if (ret == -1) {
+    if (ret == (unsigned)-1) {
         mp_raise_OSError(_errno);
     }
 
diff --git a/ports/raspberrypi/common-hal/wifi/ScannedNetworks.c b/ports/raspberrypi/common-hal/wifi/ScannedNetworks.c
index 3488fc0eb5..97299e2f74 100644
--- a/ports/raspberrypi/common-hal/wifi/ScannedNetworks.c
+++ b/ports/raspberrypi/common-hal/wifi/ScannedNetworks.c
@@ -52,7 +52,7 @@ static void scan_result_put(const cyw43_ev_scan_result_t *result) {
     }
 }
 
-static bool scan_result_available() {
+static bool scan_result_available(void) {
     return scan_full || (scan_get != scan_put);
 }
 
@@ -83,7 +83,7 @@ static int scan_result(void *env, const cyw43_ev_scan_result_t *result) {
 
 mp_obj_t common_hal_wifi_scannednetworks_next(wifi_scannednetworks_obj_t *self) {
     // no results available, wait for some
-    while (!scan_result_available(self) && cyw43_wifi_scan_active(&cyw43_state)) {
+    while (!scan_result_available() && cyw43_wifi_scan_active(&cyw43_state)) {
         RUN_BACKGROUND_TASKS;
         if (mp_hal_is_interrupted()) {
             return mp_const_none;
@@ -91,7 +91,7 @@ mp_obj_t common_hal_wifi_scannednetworks_next(wifi_scannednetworks_obj_t *self)
         cyw43_arch_poll();
     }
 
-    if (!scan_result_available(self)) {
+    if (!scan_result_available()) {
         common_hal_wifi_radio_obj.current_scan = NULL;
         return mp_const_none;
     }