Grand Central M4 Express

Overview

The Adafruit Grand Central M4 Express is an ARM development board with the form factor of an Arduino Mega. It features 70 GPIO pins, a microSDHC slot and 8MiB of QSPI Flash.

Hardware

ATSAMD51P20A ARM Cortex-M4F processor at 120 MHz
1024 KiB of flash memory and 256 KiB of RAM
8 MiB of QSPI flash
A red user LED
A RGB “NeoPixel” / WS2812B LED
A microSDHC slot (connected via SPI)
Native USB port

Supported Features

The adafruit_grand_central_m4_express 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.

`adafruit_grand_central_m4_express/samd51p20a` target

Type	Location	Description	Compatible
CPU	on-chip	ARM Cortex-M4F CPU1	`arm,cortex-m4f`
ADC	on-chip	Atmel SAM0 family ADC2	`atmel,sam0-adc`
ARM architecture	on-chip	For locating the Device ID (serial number) on Atmel SAM0 devices1	`atmel,sam0-id`
ARM architecture	on-chip	Atmel SAM0 multi-protocol (UART, SPI, I2C) SERCOM unit4	`atmel,sam0-sercom`
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 mode4	`atmel,sam0-tc32`
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 node4	`atmel,sam0-gpio`
I2C	on-chip	Atmel SAM0 series SERCOM I2C1	`atmel,sam0-i2c`
Interrupt controller	on-chip	ARMv7-M NVIC (Nested Vectored Interrupt Controller)1	`arm,v7m-nvic`
Interrupt controller	on-chip	Atmel SAM0 series External Interrupt Controller1	`atmel,sam0-eic`
LED	on-board	Group of GPIO-controlled LEDs1	`gpio-leds`
MMU / MPU	on-chip	ARMv7-M Memory Protection Unit (MPU)1	`arm,armv7m-mpu`
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 PINMUX4	`atmel,sam0-pinmux`
Pin control	on-chip	Atmel SAM0 Pinctrl Container1	`atmel,sam0-pinctrl`
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 driver1	`atmel,sam0-uart`
SPI	on-chip	Atmel SAM0 SERCOM SPI controller2	`atmel,sam0-spi`
SRAM	on-chip	Generic on-chip SRAM description2	`mmio-sram`
Timer	on-chip	ARMv7-M System Tick1	`arm,armv7m-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

The Adafruit Learning System [1] has detailed information about the board including pinouts [2] and the schematics [3].

System Clock

The SAMD51 MCU is configured to use the 32.768 kHz external oscillator with the on-chip PLL generating the 120 MHz system clock.

Serial Port

The SAMD51 MCU has 8 SERCOM based UARTs. On the Grand Central, SERCOM0 is the Zephyr console and is available on RX(PB25) and TX(PB24).

SPI Port

The SAMD51 MCU has 8 SERCOM based SPIs. On the Grand Central, SERCOM7 has been set into SPI mode to connect to devices over the SCK(PD09), MOSI(PD08), and MISO(PD11) pins. Additionally SERCOM2 has been configured as SPI to access the microSDHC card.

I2C Port

The SAMD51 MCU has 8 SERCOM based I2Cs. On the Grand Central, SERCOM3 has been configured as I2C to connect to devices over the SCL(PB21) and SDA(PB20) pins.

USB Device Port

The SAMD51 MCU has a USB device port that can be used to communicate with a host PC. See the USB device support sample applications for more, such as the USB CDC-ACM sample which sets up a virtual serial port that echos characters back to the host PC.

Programming and Debugging

The Grand Central ships with a BOSSA compatible UF2 bootloader. The bootloader can be entered by quickly tapping the reset button twice.

Flashing

Build the Zephyr kernel and the Hello World sample application:
```
west build -b adafruit_grand_central_m4_express samples/hello_world
```
Connect the Grand Central to your host computer using USB.
Connect a 3.3 V USB to serial adapter to the board and to the host. See the Serial Port section above for the board’s pin connections.
Run your favorite terminal program to listen for output. Under Linux the terminal should be /dev/ttyUSB0. For example:
```
$ minicom -D /dev/ttyUSB0 -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
Tap the reset button twice quickly to enter bootloader mode
Flash the image:
```
west build -b adafruit_grand_central_m4_express samples/hello_world
west flash
```
You should see “Hello World! adafruit_grand_central_m4_express” in your terminal.

Debugging

In addition to the built-in bootloader, the Grand Central can be flashed and debugged using a SWD probe such as the Segger J-Link.

Connect the probe to the board using the 10-pin SWD interface.

Flash the image:

west build -b adafruit_grand_central_m4_express samples/hello_world
west flash -r openocd

Start debugging:

west build -b adafruit_grand_central_m4_express samples/hello_world
west debug