Datasheet

TX and SDA (Digital pins 1 and 20)

analogWrite() PWM range

On AVR, if you set a pin's PWM with analogWrite(pin, 255) it will turn the pin fully HIGH. On the ARM cortex, it will set it

to be 255/256 so there will be very slim but still-existing pulses-to-0V. If you need the pin to be fully on, add test code

that checks if you are trying to analogWrite(pin, 255) and, instead, does a digitalWrite(pin, HIGH)

analogWrite() DAC on A0

If you are trying to use analogWrite() to control the DAC output on A0, make sure you do not have a line that sets the

pin to output.

Remove

: pinMode(A0, OUTPUT) .

Missing header files

there might be code that uses libraries that are not supported by the M0 core. For example if you have a line with

#include <util/delay.h>

you'll get an error that says

fatal error: util/delay.h: No such file or directory

#include <util/delay.h>

compilation terminated.

Error compiling.

In which case you can simply locate where the line is (the error will give you the file name and line number) and 'wrap

it' with #ifdef's so it looks like:

The above will also make sure that header file isn't included for other architectures

If the #include is in the arduino sketch itself, you can try just removing the line.

Bootloader Launching

For most other AVRs, clicking reset while plugged into USB will launch the bootloader manually, the bootloader will

time out after a few seconds. For the M0, you'll need to

double click

the button. You will see a pulsing red LED to let

you know you're in bootloader mode. Once in that mode, it wont time out! Click reset again if you want to go back to

launching code

Aligned Memory Access

This is a little less likely to happen to you but it happened to me! If you're used to 8-bit platforms, you can do this nice

thing where you can typecast variables around. e.g.

uint8_t mybuffer[4];

float f = (float)mybuffer;

#if !defined(ARDUINO_ARCH_SAM) && !defined(ARDUINO_ARCH_SAMD) && !defined(ESP8266) && !defined(ARDUINO_ARCH_STM32F2)

#include <util/delay.h>

#endif

https://learn.adafruit.com/adafruit-feather-m0-express-designed-for-circuit-python-

circuitpython

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