Has anyone seen a set of variant files that allow the nrf52840 development board that you can get at low cost on sites like ali;
With the Adafruit NRF52 core;
https://github.com/adafruit/Adafruit_nRF52_Arduino
The changes to variant.h and variant.cpp dont look too difficult, but the appropriate settings in boards.txt dont look very obvious.
I have bought some of these. If there is any knowledge out there that I need to learn to get these working please let us know.
I have found that this is something called a nice!nano and can be programmed as a keyboard with little effort. I would like to know how this works with arduino, I would like to make a gamepad with it, so very similar but not quite right. I found the appropriate bootloader: GitHub - adafruit/Adafruit_nRF52_Bootloader: USB-enabled bootloaders for the nRF52 BLE SoC chips and that's where i get a little lost.
There is no published variant files for Arduino, as far as I know, hence my question.
The clone nice!nano boards are used with the Meshtastic software, but that runs under PlatformIO.
How do you make variant.h files? I will learn it if there are resources available but my searches are coming up short.
You look at the structure of a known working variant.h file and copy it ?
The name of these well designed cheap boards:
Super mini nrf52840, similar Nice!Nano.
Perfect support for arduino Ide using:
The bootloader loads by connecting RESET Pin to GND two times within 500ms. You see a USB Drive with the name supermini (direct use for uf2 files and e.g. Circuitpython) and a usb serial port. In the Arduino IDE 2.3.3 switch to the super mini board and burn the according bootloader.
I used the 2.3.3 Arduino IDE and installed directly from github into the sketches folder.
The red led on the board ist defined as LED_BUILDIN or BLUE_LED, there is no RED_LED defined.
Pin VCC_EXT set to LOW switches the external LDO off.
I reached 5 microamps on NRF_POWER->SYSTEMOFF = 1
and
9 microamps on delay().
at 2.4V on powering direct via VCCH (on the bottom of the board VCC)
So a 2032 cab with 230mAh last for 2-3 years of delay().
The newer boards are well designed. The older ones have a resistor of 5.6k instead of 10M with causes a leakage of 700ma. You can easily remove this 5.6k resistor. This resistor is between VCCH and CE of the LDO and switches the LDO on at startup until the POWER_PIN (P0.13) ist set to LOW.
Further information:
Via lipo charger you have an additional leakage of around 20-30 microamps if you use the a lipo cell.