SAM L21 Xplained Pro Evaluation Kit

Overview

The SAM L21 Xplained Pro evaluation kit is ideal for evaluation and prototyping with the SAM L21 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.

Hardware

SAML21J18 ARM Cortex-M0+ processor at 48 MHz
32.768 kHz crystal oscillator
256 KiB flash memory, 32 KiB of SRAM, 8KB Low Power SRAM
One yellow user LED
One mechanical user push button
One reset button
On-board USB based EDBG unit with serial console

Supported Features

The saml21_xpro board supports the hardware features listed below.

on-chip / on-board: Feature integrated in the SoC / present on the board.
2 / 2: Number of instances that are enabled / disabled.
Click on the label to see the first instance of this feature in the board/SoC DTS files.
vnd,foo: Compatible string for the Devicetree binding matching the feature.
Click on the link to view the binding documentation.

`saml21_xpro/saml21j18b` target

Type	Location	Description	Compatible
CPU	on-chip	ARM Cortex-M0+ CPU1	`arm,cortex-m0+`
ADC	on-chip	Atmel SAM0 family ADC1	`atmel,sam0-adc`
ARM architecture	on-chip	For locating the Device ID (serial number) on Atmel SAM0 devices1	`atmel,sam0-id`
Clock control	on-chip	Atmel SAM0 Main Clock Controller (MCLK)1	`atmel,sam0-mclk`
	on-chip	Atmel SAM0 32kHz Oscillator Controller (OSC32KCTRL)1	`atmel,sam0-osc32kctrl`
	on-chip	Atmel SAMD0 Generic Clock Controller (GCLK)1	`atmel,sam0-gclk`
Counter	on-chip	Atmel SAM0 basic timer counter (TC) operating in 32-bit wide mode1	`atmel,sam0-tc32`
DAC	on-chip	Atmel SAM0 family DAC1	`atmel,sam0-dac`
DMA	on-chip	Atmel SAM0 DMA controller1	`atmel,sam0-dmac`
Flash controller	on-chip	Atmel SAM0 NVMC (Non-Volatile Memory Controller)1	`atmel,sam0-nvmctrl`
GPIO & Headers	on-chip	SAM0 GPIO PORT node2	`atmel,sam0-gpio`
I2C	on-chip	Atmel SAM0 series SERCOM I2C1	`atmel,sam0-i2c`
Input	on-board	Group of GPIO-bound input keys1	`gpio-keys`
Interrupt controller	on-chip	ARMv6-M NVIC (Nested Vectored Interrupt Controller) controller1	`arm,v6m-nvic`
Interrupt controller	on-chip	Atmel SAM0 series External Interrupt Controller1	`atmel,sam0-eic`
LED	on-board	Group of GPIO-controlled LEDs1	`gpio-leds`
LED	on-board	Group of PWM-controlled LEDs1	`pwm-leds`
MTD	on-chip	Flash node1	`soc-nv-flash`
Pin control	on-chip	Atmel SAM0 Pinctrl Container1	`atmel,sam0-pinctrl`
PWM	on-chip	Atmel SAM0 TCC in PWM mode1	`atmel,sam0-tcc-pwm`
RNG	on-chip	Atmel SAM RNG1	`atmel,sam-trng`
RTC	on-chip	Atmel SAM0 RTC1	`atmel,sam0-rtc`
Serial controller	on-chip	Atmel SAM0 SERCOM UART driver3	`atmel,sam0-uart`
SPI	on-chip	Atmel SAM0 SERCOM SPI controller2	`atmel,sam0-spi`
SRAM	on-chip	Generic on-chip SRAM description1	`mmio-sram`
Timer	on-chip	ARMv6-M System Tick1	`arm,armv6m-systick`
USB	on-chip	Atmel SAM0 USB in device mode1	`atmel,sam0-usb`
Watchdog	on-chip	Atmel SAM0 watchdog1	`atmel,sam0-watchdog`

Pin Mapping

The SAM L21 Xplained Pro evaluation kit has 2 GPIO controllers. These controllers are responsible for pin muxing, input/output, pull-up, etc.

For more details please refer to SAM L21 Family Datasheet [1] and the SAM L21 Xplained Pro Schematic [2].

Default Zephyr Peripheral Mapping:

SERCOM0 SPI MISO : PA04
SERCOM0 SPI MOSI : PA06
SERCOM0 SPI SCK : PA07
SERCOM1 USART TX : PA18
SERCOM1 USART RX : PA19
SERCOM2 I2C SDA : PA08
SERCOM2 I2C SCL : PA09
SERCOM3 USART TX : PA22
SERCOM3 USART RX : PA23
SERCOM4 USART TX : PB08
SERCOM4 USART RX : PB09
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 : PB10

System Clock

The SAML21 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 SAML21 MCU has six SERCOM based USARTs with two configured as USARTs in this BSP. SERCOM3 is the default Zephyr console.

SERCOM1 115200 8n1 - connected to EXT2 and EXT3
SERCOM3 115200 8n1 - connected to the onboard Atmel Embedded Debugger (EDBG)
SERCOM4 115200 8n1 - connected to EXT1

PWM

The SAML21 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 SAML21 MCU has 6 SERCOM based SPIs, with two configured as SPI in this BSP.

SERCOM0 - connected to EXT1
SERCOM5 - connected to EXT2 and EXT3

Programming and Debugging

The SAM L21 Xplained Pro comes with a Atmel Embedded Debugger (EDBG). This provides a debug interface to the SAML21 chip and is supported by OpenOCD.

Flashing

Build the Zephyr kernel and the hello_world sample application:
```
west build -b saml21_xpro samples/hello_world
```
Connect the SAM L21 Xplained Pro to your host computer using the USB debug port.
Run your favorite terminal program to listen for output. Under Linux the terminal should be /dev/ttyACM0. For example:
```
$ picocom -b 115200 /dev/ttyACM0
```
- Speed: 115200
- Data: 8 bits
- Parity: None
- Stop bits: 1
To flash an image:
```
west build -b saml21_xpro samples/hello_world
west flash
```
You should see “Hello World! saml21_xpro” in your terminal.