diff --git a/main.c b/main.c
index 7bfa565df4..7df6e293aa 100755
--- a/main.c
+++ b/main.c
@@ -69,6 +69,19 @@
 #include "shared-bindings/alarm/__init__.h"
 #endif
 
+#if CIRCUITPY_BLEIO
+#include "shared-bindings/_bleio/__init__.h"
+#include "supervisor/shared/bluetooth.h"
+#endif
+
+#if CIRCUITPY_BOARD
+#include "shared-module/board/__init__.h"
+#endif
+
+#if CIRCUITPY_CANIO
+#include "common-hal/canio/CAN.h"
+#endif
+
 #if CIRCUITPY_DISPLAYIO
 #include "shared-module/displayio/__init__.h"
 #endif
@@ -81,17 +94,8 @@
 #include "shared-module/network/__init__.h"
 #endif
 
-#if CIRCUITPY_BOARD
-#include "shared-module/board/__init__.h"
-#endif
-
-#if CIRCUITPY_BLEIO
-#include "shared-bindings/_bleio/__init__.h"
-#include "supervisor/shared/bluetooth.h"
-#endif
-
-#if CIRCUITPY_CANIO
-#include "common-hal/canio/CAN.h"
+#if CIRCUITPY_USB_CDC
+#include "shared-module/usb_cdc/__init__.h"
 #endif
 
 #if CIRCUITPY_WIFI
diff --git a/ports/atmel-samd/Makefile b/ports/atmel-samd/Makefile
index 58c1c0d60e..48724af0c8 100644
--- a/ports/atmel-samd/Makefile
+++ b/ports/atmel-samd/Makefile
@@ -122,7 +122,7 @@ CFLAGS += -ftree-vrp
 $(echo PERIPHERALS_CHIP_FAMILY=$(PERIPHERALS_CHIP_FAMILY))
 #Debugging/Optimization
 ifeq ($(DEBUG), 1)
-  CFLAGS += -ggdb3 -Og
+  CFLAGS += -ggdb3 -Og -Os
   # You may want to disable -flto if it interferes with debugging.
   CFLAGS += -flto -flto-partition=none
   # You may want to enable these flags to make setting breakpoints easier.
diff --git a/ports/raspberrypi/common-hal/pwmio/PWMOut.c b/ports/raspberrypi/common-hal/pwmio/PWMOut.c
index 6e23e236be..e861bab5a9 100644
--- a/ports/raspberrypi/common-hal/pwmio/PWMOut.c
+++ b/ports/raspberrypi/common-hal/pwmio/PWMOut.c
@@ -165,7 +165,6 @@ void common_hal_pwmio_pwmout_deinit(pwmio_pwmout_obj_t* self) {
 extern void common_hal_pwmio_pwmout_set_duty_cycle(pwmio_pwmout_obj_t* self, uint16_t duty) {
     self->duty_cycle = duty;
     uint16_t actual_duty = duty * self->top / ((1 << 16) - 1);
-    mp_printf(&mp_plat_print, "actual_duty: %d, self->top: %d\n", actual_duty, top); /// ***
     pwm_set_chan_level(self->slice, self->channel, actual_duty);
 }
 
@@ -209,7 +208,6 @@ void common_hal_pwmio_pwmout_set_frequency(pwmio_pwmout_obj_t* self, uint32_t fr
     } else {
         uint32_t top = common_hal_mcu_processor_get_frequency() / frequency;
         self->actual_frequency = common_hal_mcu_processor_get_frequency() / top;
-        mp_printf(&mp_plat_print, "high speed self->top: %d\n", top); /// ***
         self->top = top;
         pwm_set_clkdiv_int_frac(self->slice, 1, 0);
         pwm_set_wrap(self->slice, self->top - 1);
diff --git a/shared-bindings/usb_cdc/__init__.c b/shared-bindings/usb_cdc/__init__.c
index d6a70b177a..6ded44c4f7 100644
--- a/shared-bindings/usb_cdc/__init__.c
+++ b/shared-bindings/usb_cdc/__init__.c
@@ -38,18 +38,17 @@
 //|
 //| The `usb_cdc` module allows access to USB CDC (serial) communications.
 //|
-//| serial: Tuple[Serial, ...]
+//| serials: Tuple[Serial, ...]
 //| """Tuple of all CDC streams. Each item is a `Serial`."""
 //|
 
-mp_map_elem_t usb_cdc_module_globals_table[] = {
+static const mp_map_elem_t usb_cdc_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR___name__), MP_ROM_QSTR(MP_QSTR_usb_cdc) },
     { MP_ROM_QSTR(MP_QSTR_Serial),   MP_OBJ_FROM_PTR(&usb_cdc_serial_type) },
-    { MP_ROM_QSTR(MP_QSTR_serial),   mp_const_empty_tuple },
+    { MP_ROM_QSTR(MP_QSTR_serials),  MP_OBJ_FROM_PTR(&usb_cdc_serials_tuple) },
 };
 
-// This isn't const so we can set the streams dynamically.
-MP_DEFINE_MUTABLE_DICT(usb_cdc_module_globals, usb_cdc_module_globals_table);
+static MP_DEFINE_CONST_DICT(usb_cdc_module_globals, usb_cdc_module_globals_table);
 
 const mp_obj_module_t usb_cdc_module = {
     .base = { &mp_type_module },
diff --git a/shared-bindings/usb_cdc/__init__.h b/shared-bindings/usb_cdc/__init__.h
index 7938e91722..e81d243e6c 100644
--- a/shared-bindings/usb_cdc/__init__.h
+++ b/shared-bindings/usb_cdc/__init__.h
@@ -27,8 +27,6 @@
 #ifndef MICROPY_INCLUDED_SHARED_BINDINGS_USB_CDC___INIT___H
 #define MICROPY_INCLUDED_SHARED_BINDINGS_USB_CDC___INIT___H
 
-#include "py/obj.h"
-
-extern mp_obj_dict_t usb_cdc_module_globals;
+#include "shared-module/usb_cdc/__init__.h"
 
 #endif  // MICROPY_INCLUDED_SHARED_BINDINGS_USB_CDC___INIT___H
diff --git a/shared-module/usb_cdc/Serial.h b/shared-module/usb_cdc/Serial.h
index 7e3c53e8a4..60a1d1922c 100644
--- a/shared-module/usb_cdc/Serial.h
+++ b/shared-module/usb_cdc/Serial.h
@@ -3,7 +3,7 @@
  *
  * The MIT License (MIT)
  *
- * Copyright (c) 2020 Dan Halbert for Adafruit Industries
+ * Copyright (c) 2021 Dan Halbert 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
diff --git a/shared-module/usb_cdc/__init__.c b/shared-module/usb_cdc/__init__.c
index ae2412cddb..ecb5777b26 100644
--- a/shared-module/usb_cdc/__init__.c
+++ b/shared-module/usb_cdc/__init__.c
@@ -3,7 +3,7 @@
  *
  * The MIT License (MIT)
  *
- * Copyright (c) 2018 hathach for Adafruit Industries
+ * Copyright (c) 2021 Dan Halbert 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
@@ -24,32 +24,34 @@
  * THE SOFTWARE.
  */
 
-#include "shared-bindings/usb_cdc/__init__.h"
-
 #include "genhdr/autogen_usb_descriptor.h"
+#include "py/gc.h"
 #include "py/obj.h"
 #include "py/mphal.h"
 #include "py/runtime.h"
 #include "py/objtuple.h"
+#include "shared-bindings/usb_cdc/__init__.h"
 #include "shared-bindings/usb_cdc/Serial.h"
 #include "tusb.h"
 
-supervisor_allocation* usb_cdc_allocation;
+#if CFG_TUD_CDC != 2
+#error CFG_TUD_CDC must be exactly 2
+#endif
 
-static usb_cdc_serial_obj_t serial_objs[CFG_TUD_CDC];
-
-void usb_cdc_init(void) {
-
-    serial_obj_ptrs *usb_cdc_serial_obj_t[CFG_TUD_CDC];
-
-    for (size_t i = 0; i < CFG_TUD_CDC; i++) {
-        serial_objs[i].base.type = &usb_cdc_serial_type;
-        serial_objs[i].idx = i;
-        serial_obj_ptrs[i] = &serial_objs[i];
+static const usb_cdc_serial_obj_t serial_objs[CFG_TUD_CDC] = {
+    {   .base.type = &usb_cdc_serial_type,
+        .idx = 0,
+    }, {
+        .base.type = &usb_cdc_serial_type,
+        .idx = 1,
     }
+};
 
-    serials_tuple->base.type = mp_obj_new_tuple(CFG_TUD_CDC, serials);
-
-    repl->base.type =
-    repl->idx = 0;    mp_map_lookup(&usb_cdc_module_globals.map, MP_ROM_QSTR(MP_QSTR_serial), MP_MAP_LOOKUP)->value = MP_OBJ_FROM_PTR(serials_tuple);
-}
+const mp_rom_obj_tuple_t usb_cdc_serials_tuple = {
+    .base.type = &mp_type_tuple,
+    .len = CFG_TUD_CDC,
+    .items = {
+        &serial_objs[0],
+        &serial_objs[1],
+    },
+};
diff --git a/shared-module/usb_cdc/__init__.h b/shared-module/usb_cdc/__init__.h
index 02b48e1165..9de3eb2faa 100644
--- a/shared-module/usb_cdc/__init__.h
+++ b/shared-module/usb_cdc/__init__.h
@@ -27,6 +27,8 @@
 #ifndef SHARED_MODULE_USB_CDC___INIT___H
 #define SHARED_MODULE_USB_CDC___INIT___H
 
-void usb_cdc_init(void);
+#include "py/objtuple.h"
+
+extern const mp_rom_obj_tuple_t usb_cdc_serials_tuple;
 
 #endif /* SHARED_MODULE_USB_CDC___INIT___H */
diff --git a/supervisor/shared/usb/usb.c b/supervisor/shared/usb/usb.c
index 43564d5d5c..af48f46737 100644
--- a/supervisor/shared/usb/usb.c
+++ b/supervisor/shared/usb/usb.c
@@ -26,7 +26,6 @@
 
 #include "py/objstr.h"
 #include "shared-bindings/microcontroller/Processor.h"
-#include "shared-module/usb_midi/__init__.h"
 #include "supervisor/background_callback.h"
 #include "supervisor/port.h"
 #include "supervisor/serial.h"
@@ -35,6 +34,10 @@
 #include "lib/utils/interrupt_char.h"
 #include "lib/mp-readline/readline.h"
 
+#if CIRCUITPY_USB_MIDI
+#include "shared-module/usb_midi/__init__.h"
+#endif
+
 #include "tusb.h"
 
 #if CIRCUITPY_USB_VENDOR