XIAO nRF52840

The Seeed Studio XIAO nRF52840 is a general purpose board supplied by Seeed Studio and it is compatible with the Nordic nRF52840 ecosystem as they share the same MCU.

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Features

  • Nordic nRF52840, ARM® Cortex®-M4 32-bit processor with FPU, 64 MHz

  • 256 KB RAM,1MB Flash 2MB onboard Flash

  • Bluetooth 5.0/BLE/NFC

  • 1xUART, 1xI2C, 1xSPI, 1xNFC, 1xSWD, 11xGPIO(PWM)

  • USB Type-C interface

  • 1 RGB LED, 1 charge LED

  • 1 RESET button

Serial Console

By default, a serial console appears on pins 6 (TX P1.11) and pin 7 (RX P1.12). This console runs a 115200-8N1. The board can be configured to use the USB connection as the serial console.

User LED

The RGB LED is connected as follows:

Color

Pin

RED

P0.26

GREEN

P0.30

BLUE

P0.6

Buttons

The Reset button can be used to enter bootloader mode by rapidly clicking it twice. Then, it will enumerate as a storage device to a computer connected via USB. Saving a .UF2 file to this device will replace the Flash ROM contents on the nRF52840.

Pin Mapping

Pads numbered anticlockwise from USB connector.

Pad

Signal

Notes

0

P0.02

D0/A0

1

P0.03

D1/A1

2

P0.28

D2/A2

3

P0.29

D3/A3

4

P0.04

D4/SDA

5

P0.05

D5/SCL

6

P1.11

Default TX for UART0 serial console

7

P1.12

Default RX for UART0 serial console

8

P1.13

D8/SCK

9

P1.14

D9/MISO

10

P1.15

D10/MOSI

11

3V3

Power output to peripherals

12

Ground

13

VIN

+5V Supply to board

Power Supply

The working voltage of the MCU is 3.3V. Voltage input connected to general I/O pins may cause chip damage if it’s higher than 3.3V.

Installation

  1. Download UF2 Tools:

$ git clone https://github.com/microsoft/uf2.git

  1. Configure and build NuttX:

$ git clone https://github.com/apache/nuttx.git nuttx
$ git clone https://github.com/apache/nuttx-apps.git apps
$ cd nuttx
$ make distclean
$ ./tools/configure.sh xiao-nrf52840:nsh
$ make V=1

  1. Convert nuttx.hex to UF2 format using U2F Tools:

$ python3 uf2/utils/uf2conv.py -c -f 0xADA52840 -i nuttx.hex -o nuttx.uf2

4. Connect the Seeed Studio XIAO nRF52840, and enter bootloader mode by rapidly clicking it twice. The board will be detected as a USB Mass Storage Device. Then copy “nuttx.uf2” into the device.

  1. To access the console, TX and RX pins must be connected to the device such as USB-serial converter.

Configurations

nsh

Basic NuttShell configuration (console enabled in UART0, at 115200 bps).

usbnsh

Basic NuttShell configuration using CDC/ACM serial (console enabled in USB Port, at 115200 bps).

jumbo

This configuration enabled NuttShell via USB and enabled leds and gpio examples:

Testing leds:

$nsh> leds
leds_main: Starting the led_daemon
leds_main: led_daemon started

led_daemon (pid# 3): Running
led_daemon: Opening /dev/userleds
led_daemon: Supported LEDs 0x07
led_daemon: LED set 0x01
$nsh> led_daemon: LED set 0x02
led_daemon: LED set 0x03
led_daemon: LED set 0x04
led_daemon: LED set 0x05
led_daemon: LED set 0x06
led_daemon: LED set 0x07

Testing gpios:

PIN/GPIO

Mode

Device

D0/P0.02

Input

/dev/gpio0

D2/P0.28

Output

/dev/gpio1

D1/P0.03

Input

/dev/gpio2

 
$nsh> gpio /dev/gpio0
Driver: /dev/gpio0
  Input pin:     Value=0
$nsh> gpio /dev/gpio0
Driver: /dev/gpio0
  Input pin:     Value=1

$nsh> gpio -o 0 /dev/gpio1
Driver: /dev/gpio1
  Output pin:    Value=1
  Writing:       Value=0
  Verify:        Value=0

$nsh> gpio -w 1 /dev/gpio2
Driver: /dev/gpio2
  Interrupt pin: Value=0
  Verify:        Value=1