Sparkfun SAMD21 Dev Breakout

Overview

The SparkFun SAMD21 dev breakout board is an arduino form factor development board. Designed to be a more powerful arduino. It shares the arduino form factor and gpio footprint. Based on the ATSAMD21G18 MCU, it runs a 32-Bit Arm Cortex-M0+ at up to 48MHz. More information can be found on the SAMD21 dev breakout specification website [1].

Hardware

ATSAMD21G18 32-bit/48MHz ARM Cortex-M0+
256KB Flash Memory
32KB SRAM
32KB of EEPROM (emulated in Flash)
30 GPIO Count with Arduino R3 footprint
6x Configurable SERCOM ports
- USART with full-duplex and single-wire half-duplex configuration
- I2C up to 3.4 MHz
- SPI
- LIN client
One 12-bit, 350ksps Analog-to-Digital Converter (ADC) with up to 20 channels
- Differential and single-ended input
- 1/2x to 16x programmable gain stage
- Automatic offset and gain error compensation
- Oversampling and decimation in hardware to support 13-bit, 14-bit, 15-bit, or 16-bit resolution
One two-channel Inter-IC Sound (I2S) interface
32-bit Real Time Counter (RTC) with clock/calendar function
Watchdog Timer (WDT)
CRC-32 generator
One full-speed (12 Mbps) Universal Serial Bus (USB) 2.0 interface
- Embedded host and device function
- Eight endpoint

Supported Features

The sparkfun_samd21_breakout 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.

`sparkfun_samd21_breakout/samd21g18a` 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	Atmel SAM0 multi-protocol (UART, SPI, I2C) SERCOM unit3	`atmel,sam0-sercom`
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`
Clock control	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 mode2	`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`
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`
MTD	on-chip	Flash node1	`soc-nv-flash`
MTD	on-board	Fixed partitions of a flash (or other non-volatile storage) memory1	`fixed-partitions`
Pin control	on-chip	Atmel SAM0 PINMUX2	`atmel,sam0-pinmux`
Pin control	on-chip	Atmel SAM0 Pinctrl Container1	`atmel,sam0-pinctrl`
RTC	on-chip	Atmel SAM0 RTC1	`atmel,sam0-rtc`
Serial controller	on-chip	Atmel SAM0 SERCOM UART driver1	`atmel,sam0-uart`
SPI	on-chip	Atmel SAM0 SERCOM SPI controller1	`atmel,sam0-spi`
SRAM	on-chip	Generic on-chip SRAM1	`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`

Connections and IOs

LED

Led0 (blue) = D13

Serial IO

sparkfun_spi = sercom4
sparkfun_i2c = sercom3
sparkfun_serial = sercom0
sparkfun_dac = dac0
sparkfun_adc = adc

Programming and Debugging

The sparkfun_samd21_breakout board supports the runners and associated west commands listed below.

	flash	debug	attach	rtt	debugserver
blackmagicprobe	✅	✅	✅
bossac	✅ (default)
openocd	✅	✅ (default)	✅	✅	✅

Applications for the sparkfun_samd21_breakout/samd21g18a board target can be built, flashed, and debugged in the usual way. See Building an Application and Run an Application for more details on building and running.

Flashing

To enter flash mode, connect the board via the micro USB to the host, press the reset button twice. The onboard blue led should slowly fade, indicating flash mode.

Flashing Application

This board utilizes the UF2 bootloader, which flashes firmware via uploaded a file to board via mass-storage device. See uf2-samdx1 bootloader info [3].

Flashing Bootloader

If flashing the bootloader you can use a Jeff Probe/Black Magic Debugger to connect via SWD. Note this can also be used to recover a bricked board. Bootloader source code repo is available at: uf2-samdx1 bootloader repo [2].

Build bootloader for sparkfun samd21 dev board:

git clone https://github.com/adafruit/uf2-samdx1
cd uf2-samdx1
make BOARD=sparkfun-samd21-dev

Place commands to flash bootloader into a gdb_init file:

target extended-remote /dev/ttyACM<num> # check in dmesg
monitor swdp_scan # make sure this works too, cable could be upside down
attach 1
load

Connect the debug probe and run:

# Run gdb with your gdb_init script:
arm-none-eabi-gdb bootloader-sparkfun-samd21-dev-<bootloader-version>.elf -x gdb_init

Debugging

Using the Jeff Probe/Black Magic Debugger, you can connect SWD and run gdb through the serial connection. See above for example instructions for flashing the bootloader. Otherwise, use west to debug.

Debug with west:

west debug -r blackmagicprobe