Adafruit Feather nRF52840 Express

This is a beta release of support for the Adafruit Feather nRF52840 Express (https://www.adafruit.com/product/4062)

Supported mbed-os version: 6.3.0

The following features have been tested:

• LED's
• SPI and SPIM
• Console output

Features not specifically tested:

• I2C
• QSPI
• QSPI Flash
• anything else I have missed

Example application

This repository includes blinky.cpp as an example application to demonstrate how to use the Adafruit nrf52840 Feather custom board. It's expected to work out of the box using both Mbed CLI and Mbed Studio. Note this test application can be ignored using the MBED_BLINKY_EXAMPLE macro in mbed_app.json, so you can add your own files and application on top of this project.

You can follow these steps to import and compile with Mbed CLI:

mbed import https://github.com/winneymj/mbed-os-ADAFRUIT-NRF52840-FEATHER.git
mbed compile -t GCC_ARM -m ADAFRUIT_NRF52840_FEATHER

I suggest you rename the created directory "mbed-os-ADAFRUIT-NRF52840-FEATHER" to be more reflective of your project.

Building and Flash board in Visual Studio Code

prerequisites:

• python3

Installation (Windows only):

• Install adafruit-nrfutil

pip3 install --user adafruit-nrfutil

• Locate the adafruit-nrfutil.exe and add to path

To build and flash under Visual Studio Code

• update Visual Studio Code tasks.json to include following configuration inside the tasks array:

    "tasks": [
        {
            "label": "compile release",
            "group": "build",
            "command": "mbed",
            "args": [
                "compile",
                "--profile=release",
                "-v",
                "-t",
                "GCC_ARM",
                "-m",
                "ADAFRUIT_NRF52840_FEATHER"
            ]
        },
        {
            "label": "ada-nrfutil app hex to DFU zip",
            "group": "build",
            "command": "adafruit-nrfutil",
            "args": [
                "dfu",
                "genpkg",
                "--dev-type",
                "0x0052",
                "--sd-req",
                "0x00B6",
                "--application",
                "${workspaceFolder}\\BUILD\\ADAFRUIT_NRF52840_FEATHER\\GCC_ARM-RELEASE\\${workspaceFolderBasename}_application.hex",
                "${workspaceFolder}\\BUILD\\ADAFRUIT_NRF52840_FEATHER\\GCC_ARM-RELEASE\\${workspaceFolderBasename}_application.hex.zip"
            ],
            "presentation": {
                "echo": true,
                "reveal": "always",
                "focus": false,
                "panel": "shared",
                "showReuseMessage": true,
                "clear": false
            },
        },
        {
            "label": "ada-nrfutil flash DFU pkg",
            "group": "build",
            "command": "adafruit-nrfutil",
            "args": [
                "--verbose",
                "dfu",
                "serial",
                "-pkg",
                "${workspaceFolder}\\BUILD\\ADAFRUIT_NRF52840_FEATHER\\GCC_ARM-RELEASE\\${workspaceFolderBasename}_application.hex.zip",
                "-p",
                "COM7",
                "-b",
                "115200",
                "--singlebank"
            ]
        },
        {
            "label": "Build Release",
            "group": {
                "kind": "build",
                "isDefault": true
            },
            "dependsOrder": "sequence",
            "dependsOn": ["compile release", "ada-nrfutil app hex to DFU zip", "ada-nrfutil flash DFU pkg"]
        }
    ]

Compiling and Building

• Connect Adafruit board to computer via USB cable.
• Check the virtual COM port it opened (on my laptop was COM7) but may be different on yours. If it is not COM7 then make sure to change the tasks.json file "ada-nrfutil flash DFU pkg" section port to match.
• In Visual Studio Code execute a build. (SHIFT + CTRL + B).
• Whilst waiting for build press the reset button on Adafruit twice quickly to enter DFU programming mode. Neopixel LED will be green.
• Watch Console output for compile, hex to DFU zip and eventual upload to board.

Enabling console printf back to host computer via USB

To use debug printf statements and see them on your host computer you need to include into your main.cpp the header file USBConsole.h as below:

#include "USBConsole.h"

you can then use the standard printf:

printf("main: ENTER\r\n");

To view the output you will need to use a terminal/telnet client such as Putty. When the Adafruit board is running with the USBConsole enabled program a virtual COM port will be opened (COM8 on my computer) and the output streamed. The program suspends until the COM port is opened....so remember to do this if you have used the USBConsole, otherwise it will look like you program is not working.

You can remove the header file (USBConsole.h)...and leave the printf's in place to allow the program to run as normal and not suspend, and of course without the output.