View source for Nordic nRF52840

I have an nRF52840-DK developer board ($49) and 2 of the Nordic tiny dev boards in the USB form factor, [https://www.nordicsemi.com/Products/Development-hardware/nrf52840-dongle NRF52840-DONGLE] from Digikey, about $10 each.

Nordic [https://infocenter.nordicsemi.com/index.jsp?topic=/ug_nrf52840_dongle/UG/nrf52840_Dongle/getting_started.html Getting started]guide

They can do Zigbee, which is why I got them and of course have done nothing with so far.

== Loading Circuit Python ==

The nrf52840 supports USB making it easy to program. 

I can put CircuitPython on it.
Install the dev tools: [https://www.nordicsemi.com/Software-and-Tools/Development-Tools/nRF-Connect-for-desktop nRF Connect for desktop]
Use that to install the [https://infocenter.nordicsemi.com/index.jsp?topic=%2Fug_nc_programmer%2FUG%2Fnrf_connect_programmer%2Fncp_introduction.html programmer].

I think it's now possible to use an Adafruit fork of the Nordic utility to get the Circuit Python bootloader installed.

The other option is to use either a very expensive Segger J-Link (+$800) or the $49 Nordic nRF52840-DK development board. I got one of the $49 boards, here we go. Alas it has a weird tiny connector so, another cable? Oy.

=== Install bootloader ===

https://github.com/adafruit/Adafruit_nRF52_Bootloader/blob/master/README.md

 conda create -n adafruit-nrf
 conda activate adafruit-nrf
 pip3 install adafruit-nrfutil

Download a bootloader from https://github.com/adafruit/Adafruit_nRF52_Bootloader/releases
I used https://github.com/adafruit/Adafruit_nRF52_Bootloader/releases/download/0.6.4/mdk_nrf52840_dongle_bootloader-0.6.4_s140_6.1.1.zip

 adafruit-nrfutil dfu serial -p com3 -pkg *hex

After getting the board to connect as a mass storage device then I can put
[https://circuitpython.org/board/pca10059/ Circuit Python] onto it.
I think for this board, I will need to install their bootloader too.

== My first project: HID Keyboard ==

When I got CircuitPython running I put the "Hello world" app on there and changed it to 
playback my long and complex password. That's it for this project!

It powers on and becomes an HID keyboard in about 2 seconds and then on each button press it plays my password. Ta-da!

Other ways I could do this: I could use a Adafruit RP2040 Feather for $10. I already got it going on an Adafruit Circuit Playground Express $25. 

It's about what's in my <s>junk drawer</s> inventory, not what it costs. The nRF is a handy form factor. A Pi Zero for $5 would work but I don't own one and it would require booting Linux so it would be too slow. I did try out the HID keyboard thing on a Pi Zero W. Too complicated. A $4 Pico would work but does it have a button? (No.)

== JTAG ==
The DK board has a J-Link Segger JTAG built in. The drivers install as part of the toolkit that's now installed on [[Pearl]].

== Resources ==

https://www.nordicsemi.com/Products/Development-hardware/nRF52840-DK/GetStarted#infotabs

RIOT operating system https://doc.riot-os.org/group__boards__nrf52840-mdk-dongle.html

Nordic documentation https://docs.nordicsemi.com/