SAM D21 Xplained Pro Evaluation Kit

Overview

The SAM D21 Xplained Pro evaluation kit is ideal for evaluation and prototyping with the SAM D21 Cortex®-M0+ processor-based microcontrollers. The kit includes Atmel’s Embedded Debugger (EDBG), which provides a full debug interface without the need for additional hardware.

ATSAMD21-XPRO

ATSAMD21-XPRO (Credit: Microchip Technology [1])

Hardware

  • ATSAMD21J18 ARM Cortex-M0+ processor at 48 MHz

  • 32.768 kHz crystal oscillator

  • 256 KiB flash memory and 32 KiB of RAM

  • One yellow user LED

  • One mechanical user push button

  • One reset button

  • On-board USB based EDBG unit with serial console

Supported Features

The atsamd21_xpro board configuration supports the following hardware features:

Interface

Controller

Driver / Component

NVIC

on-chip

nested vector interrupt controller

Flash

on-chip

Can be used with LittleFS to store files

SYSTICK

on-chip

systick

WDT

on-chip

Watchdog

ADC

on-chip

Analog to Digital Converter

GPIO

on-chip

I/O ports

PWM

on-chip

Pulse Width Modulation

USART

on-chip

Serial ports

I2C

on-chip

I2C ports

SPI

on-chip

Serial Peripheral Interface ports

USB

on-chip

Universal Serial Bus device ports

Other hardware features are not currently supported by Zephyr.

The default configuration can be found in the Kconfig boards/arm/atsamd21_xpro/atsamd21_xpro_defconfig.

Pin Mapping

The SAM D21 Xplained Pro evaluation kit has 3 GPIO controllers. These controllers are responsible for pin muxing, input/output, pull-up, etc.

For more details please refer to SAM D21 Family Datasheet [2] and the SAM D21 Xplained Pro Schematic [3].

ATSAMD21-XPRO-pinout

Default Zephyr Peripheral Mapping:

  • SERCOM0 USART TX : PA10

  • SERCOM0 USART RX : PA11

  • SERCOM1 USART TX : PA16

  • SERCOM1 USART RX : PA19

  • SERCOM2 I2C SDA : PA08

  • SERCOM2 I2C SCL : PA09

  • SERCOM3 USART TX : PA22

  • SERCOM3 USART RX : PA23

  • SERCOM5 SPI MISO : PB16

  • SERCOM5 SPI MOSI : PB22

  • SERCOM5 SPI SCK : PB23

  • USB DP : PA25

  • USB DM : PA24

  • GPIO SPI CS : PB17

  • GPIO/PWM LED0 : PB30

System Clock

The SAMD21 MCU is configured to use the 32.768 kHz external oscillator with the on-chip PLL generating the 48 MHz system clock.

Serial Port

The SAMD21 MCU has six SERCOM based USARTs with three configured as USARTs in this BSP. SERCOM3 is the default Zephyr console.

  • SERCOM0 9600 8n1

  • SERCOM1 115200 8n1

  • SERCOM3 115200 8n1 connected to the onboard Atmel Embedded Debugger (EDBG)

PWM

The SAMD21 MCU has 3 TCC based PWM units with up to 4 outputs each and a period of 24 bits or 16 bits. If CONFIG_PWM_SAM0_TCC is enabled then LED0 is driven by TCC0 instead of by GPIO.

SPI Port

The SAMD21 MCU has 6 SERCOM based SPIs. On the SAM D21 Xplained Pro, SERCOM5 is connected to an 8 megabit SPI flash.

Programming and Debugging

The SAM D21 Xplained Pro comes with a Atmel Embedded Debugger (EDBG). This provides a debug interface to the SAMD21 chip and is supported by OpenOCD.

Flashing

  1. Build the Zephyr kernel and the hello_world sample application:

    west build -b atsamd21_xpro samples/hello_world

  2. Connect the SAM D21 Xplained Pro to your host computer using the USB debug port.

  3. Run your favorite terminal program to listen for output. Under Linux the terminal should be /dev/ttyACM0. For example:

    $ minicom -D /dev/ttyACM0 -o

    The -o option tells minicom not to send the modem initialization string. Connection should be configured as follows:

    • Speed: 115200

    • Data: 8 bits

    • Parity: None

    • Stop bits: 1

  4. To flash an image:

    west build -b atsamd21_xpro samples/hello_world
west flash

    You should see “Hello World! atsamd21_xpro” in your terminal.

References