SercomSPISlave

Introduction

This is a Sercom SPI library used for ATSAMD21 boards, such as the Arduino Zero, Arduino MKR Zero and Adafruit Feather M0. It provides functions to setup SPI Slaves using Sercom0, Sercom1, Sercom2, Sercom3, Sercom4 and Sercom5.

To use the library with the Arduino IDE, simply install it via the Arduino Library Manager or clone or copy the the folder into the Arduino library folder.

Examples are provided to set up a:

• Sercom0 SPI Slave
• Sercom1 SPI Slave
• Sercom4 SPI Slave

Why would I set up a board as an SPI slave?

Setting up a board as an SPI slave can be used to for instance communicate over SPI between a Raspberry Pi (SPI master) and an ATSAMD21-based board (SPI slave).

Hardware implementation

Any Sercom pin on an ATSAMD21 board is supported by this library.

The pins available for each Sercom are easily seen using Visual Studio Code. Please try it out by modifying the example Sercom4SPISlave in Visual Studio Code. Remove ::PA12 and type :: instead. You will find all pins that can be used for this Sercom PAD listed for autocompletion.

Note Not all pins are physically available on each ATSAMD21-based board.

Note Not all Sercom may be available to set up an SPI slave on each ATSAMD21-based board, as some Sercom may already be used by default for other communication interfaces.

The pins used in the examples are:

Sercom0

SPI pin	description	ATSAMD21 pin
MOSI	Master Out Slave In	PA08
SCK	Serial Clock	PA09
SS	Slave Select	PA10
MISO	Master In Slave Out	PA11

Sercom1

SPI pin	description	ATSAMD21 pin
MOSI	Master Out Slave In	PA16
SCK	Serial Clock	PA17
SS	Slave Select	PA18
MISO	Master In Slave Out	PA19

Sercom4

SPI pin	description	ATSAMD21 pin
MOSI	Master Out Slave In	PA12
SCK	Serial Clock	PB09
SS	Slave Select	PB10
MISO	Master In Slave Out	PB11

Example: Adafruit Feather M0

To setup a Sercom4 SPI slave on an Adafruit Feather M0, connect the pins as follows:

SPI pin	ATSAMD21 pin	Arduino pin	Sercom#/PAD[#]
MOSI	PA12	PIN22	Sercom4/PAD[0]
SCK	PB09	PIN16	Sercom4/PAD[1]
SS	PB10	PIN23	Sercom4/PAD[2]
MISO	PB11	PIN24	Sercom4/PAD[3]

The pinout of the Adafruit Feather M0 is found here.

Note On the Adafruit Feather M0 the pin descriptions on the board do not match the names of the Sercom4 pins.

References

• The development of this code was made possible with the support I received on the Arduino Forum in the following topic. My username is Maverick123.

• The datasheet of the Atmel SAM D21G microcontroller is found here. See Table 6-1 "PORT Function Multiplexing" to find the pins that can be used for Sercom0, Sercom1, Sercom2, Sercom3, Sercom4 and Sercom5.

• A detailed description how to use the table is found here.

Further references

• This repository aims to follow the Arduino CLI library specification.

• This repository aims to follow the Google C++ Style Guide.

• This repository adheres to Semantic Versioning Specification 2.0.0.