Summary

Schematic & Reference Design

EAGLE files: arduino-M0-reference-design.zip

Schematic: arduino-M0-schematic.pdf

Power

Memory

The ATSAMD21G18 has 256 KB of flash program memory (with 4 KB used for the bootloader). The bootloader is factory pre burnt by Atmel and is stored in a dedicated ROM memory. The bootloader is protected using the NVM fuse.

It also carries 32 KB of SRAM and up to 16KB by emulation of EEPROM (which can be read and written with the EEPROM library).

Input and Output

Each of the 14 digital i/o pins on the M0 can be used as an input or output, using pinMode(), digitalWrite(), and digitalRead() functions. They operate at 3.3 volts. 7mA as maximum DC current for I/O pins and an internal pull-up resistor (disconnected by default) of 20-60 kOhms. In addition, some pins have specialized functions:

• Serial: 0 (RX) and 1 (TX). Used to receive (RX) and transmit (TX) TTL serial data using the ATSAMD21G18 hardware serial capability. Note that on the M0, the Serial class refers to USB (CDC) communication; for serial on pins 0 and 1, use the Serial1 class.
• TWI: SDA and SCL. Support TWI communication using the Wire library.
• PWM: Pins 2 to 13 Provide 8-bit PWM output with the analogWrite() function. The resolution of the PWM can be changed with the analogWriteResolution() function.
  Note1 The pins 4 and 10 can not be used simultaneously as PWM.
  Note2 The pins 5 and 12 can not be used simultaneously as PWM.
• SPI: on the ICSP header. These pins support SPI communication using the SPI library. Note that the SPI pins are not connected to any of the digital I/O pins as they are on the Uno, They are only available on the ICSP connector. This means that if you have a shield that uses SPI, but does NOT have a 6-pin ICSP connector that connects to the M0's 6-pin ICSP header, the shield will not work.
• LED: 13. There is a built-in LED connected to digital pin 13. When the pin is HIGH value, the LED is on, when the pin is LOW, it's off.
• Analog Inputs: A0-A5. The M0 has 6 analog inputs, labeled A0 through A5. Pins A0-A5 appear in the same locations as on the Uno; Each analog input provides 12 bits of resolution (i.e. 4096 different values). By default the analog inputs measure from ground to 3.3 volts, though is it possible to change the upper end of their range using the AREF pin and the analogReference() function.
• DAC: pin A0 provides true analog outputs with 10-bits resolution (1023 levels) with the analogWrite() function. This pin can be used to create an audio output using the Audio library.
• Reset: Bring this line LOW to reset the microcontroller. This is typically used to add a reset button when shields are used that block the one already present on the board.

Communication

The Arduino M0 has a number of facilities for communicating with a computer, with another Arduino or other microcontrollers, and with different devices like phones, tablets, cameras and so on. The SAMD21 provides one hardware UART and three hardware USARTs for 3.3V serial communication.

The Arduino software includes a serial monitor allowing simple textual data to be sent to and from the board. The RX and TX LEDs on the board will flash when data is being transmitted via the ATSAMD21G18 chip and USB connection to the computer (but not for serial communication on pins 0 and 1).

The Native USB port is connected to the SAMD21. It allows for serial (CDC) communication over USB. This provides a serial connection to the Serial Monitor or other applications on your computer.

The SAMD21 also supports TWI and SPI communication. The Arduino software includes a Wire library to simplify use of the TWI bus. For SPI communication, you can use the SPI library.

Programming

The Arduino M0 can be programmed with the Arduino software (download).  
If you use Linux-based OS follow the guide Arduino IDE on Linux-based OS.

Uploading sketches to the SAMD21 is different from how it works with the AVR microcontrollers found in other Arduino boards: the flash memory needs to be erased before being re-programmed. Upload operation is managed by a dedicated ROM area on the SAMD21.

USB port: To use this port, select "Arduino M0 (Native USB Port)" as your board in the Arduino IDE. The Native USB port is connected directly to the SAMD21. Connect the M0 Native USB port (the one closest to the reset button) to your computer. Opening and closing the Native port at 1200bps triggers a 'soft erase' procedure: the flash memory is erased and the board is restarted with the boot loader. Opening and closing the native port at a different baudrate will not reset the SAMD21.

USB Overcurrent Protection

The M0 has a resettable polyfuse that protects your computer's USB ports from shorts and overcurrent. Although most computers provide their own internal protection, the fuse provides an extra layer of protection. If more than 500 mA flows through to the USB port, the fuse will automatically break the connection until the short or overload is removed.

Physical Characteristics

The maximum length and width of the M0  PCB are 2.7 and 2.1 inches respectively, with the USB connector and power jack extending beyond the former dimension. Four screw holes allow the board to be attached to a surface or case. Note that the distance between digital pins 7 and 8 is 160 mil (0.16"), not an even multiple of the 100 mil spacing of the other pins.

Conformity Declaration

FCC

RoHS

CE