Need help loading micropython onto Adafruit Feather nRF52840

[JDRBoston]

Can someone please give me advice/instructions on how to load Micropython onto the Adafruit Feather nRF52840? There are no instructions at https://micropython.org/download/FEATHER52/. I've used urf2conv.py / uf2families.json and the nrf/FEATERH52 micropython v1.23.0 hex to make a uf2-compatible file, firmware.uf2.zip. But when I dragged it onto the UF2 bootloader folder, it failed. The board serial port disappeared, and when I rebooted it, I saw that this method erased the SoftDevice. The UF2 Bootloader version is 0.9.0.

I needed to re-load the SoftDevice (S140 6.1.1) using the Arduino IDE onto the board to flash Circuitpython onto it. But I'd like to load it with Micropython instead. I'd appreciate instructions/advice.

I'm using a Mac OS 12.6.

Thank you, Jay

[andrewleech]

Yes the nrf port hasn't had as much development as some others so gaps in docs like this are common.

Many of the default builds for nrf generally don't include SD support at all so flash straight over it looks you saw.

It can be recompiled for SD at which point the SD can be flashed automatically too:

https://github.com/micropython/micropython/tree/master/ports/nrf#compile-and-flash-with-bluetooth-stack

It would certainly be helpful if the uf2 conversion could be done automatically for boards like this that need it by default, that would be a worthwhile addition to the Makefile.

[rkompass]

I had the same/similar problem. See this discussion.

[jkorte-dev]

If the board uses the Adafruit UF2 Bootloader with SoftDevice (S140 6.1.1) and you convert the firmware.hex with urf2conv.py
uf2conv.py -c -f 0xADA52840 -o firmware.uf2 firmware.hex
it should report the start address as 0x26000. (see https://github.com/adafruit/Adafruit_nRF52_Bootloader for details). U2F_INO.TXT shows all version information of the bootloader.

If uf2conv.py does not report 0x26000 linking is not correct. I had a similar problem with a Supermini nrf52840 an solved it by adding
LD_FILES += boards/[MY_BOARD_NAME]/bootloader.ld boards/nrf52840_1M_256k.ld
to mpconfigboard.mk
plus the the linker script (I found in the boards directory of SEEED_XIAO_NRF52)
https://github.com/micropython/micropython/blob/master/ports/nrf/boards/SEEED_XIAO_NRF52/XIAO_bootloader.ld

[JDRBoston]

Thank you for all the suggestions! It is taking me a while to digest them, as I do not have experience in making micropython binary. I have worked primarily with micropython on the ESP32 and relied on the kind micropython builds made by others and their easy loading using esptool. These are my first tentative steps in building micropython using the Mac...

Thank you, jkorte-dev! I tried your suggestion - the Adafruit Feather nRF2 express board has a UF2 Bootloader 0.9.0 with SoftDevice S140 6.1.1 - using the indicated uf2conv.py instruction with the FEATHER52-20240602-v1.23.0.hex build. But Terminal reported the resulting uf2 start address at 0x0 and not 0x26000. So the linking is probably not correct as you indicated. By any chance, can I have a zip copy of your firmware.uf2 file just to test whether it can load onto the device? If it does, then I'll do a deep dive into how to build microsoft with the instructions you all mentioned.

[jkorte-dev]

The micropython firmware you tried is for the nRF528320 version of the Feather (Adafruit Feather nRF52). I have overseen that. Here you can find a build for a nrRF52840 board using UF2 Bootloader 0.9.0 with SoftDevice S140:
https://github.com/jkorte-dev/micropython-board-NRF52840/tree/main/firmware/
Please let me know if it works for your Feather board. If your board features a NeoPixel rgb LED please test it with the neopixel module included in the firmware. If your test was successful you can do me a favor and report you result in my PR (#15482) which was the base for the build. Thank you very much

[JDRBoston]

Thank you! You are right, its a nRF52840 version of the feather - https://www.adafruit.com/product/4062 .

[jkorte-dev]

Then we have good chance that the build will work, though default led pin assignment will be wrong. When using thonny there will be a message that RTC is missing. Thats because nrf port lacks RTC support.

[JDRBoston]

I downloaded your kindly provided uf2 file and dropped in onto the boot folder. This caused a transfer and the folder to close. But then the device no longer exposes a port for me to connect via Terminal / Thonny, even with a power cycle. But this time when I put the board back into boot mode, the SoftDevice is preserved, showing version S 140 6.1.1. When I tried to copy my uf2 file before, it seemed to overwtie the SoftDevice. When entering boot mode, the device reveals an usbmodem401 port. When I connect to that port, there is no response from the device - I cannot get to REPL.

Do you have other suggestions? Thank you.

[jkorte-dev]

If no usbmodem device shows up when you are using my uf2 file it is very likely that the firmware could not boot. when you still can enter boot mode I would try the a circuitpython build for your board to see if it boots. because if it works soft device and bootloader are ok.
what do you mean with the "uf2 file before" is it the one with the wrong start address ?

[JDRBoston]

Thank you, jkorte-dev - I was able to load your uf2 build onto the nRF52! I was successful after reloading the bootloader using the Arduino IDE. I can now get to REPL via Terminal and Thonny. I appreciate you letting me borrow your code to test this. This is great - now I will learn how to build the hex on the Mac, incorporating your tips, generating the uf2 using your instructions, and see if I can do it myself.

[jkorte-dev]

I am happy to hear that you had success loading the firmware. The Neopixel Pin on your board is P0.16 which resolves to CPU Pin 16.
Unfortunately I did not define the Pin because it is not layout on my board. I'll make a new build for you.

[jkorte-dev]

I have updated the firmware file micropython-NRF52840-supermini-v1.24.0-preview.uf2 . It should now define all pins of your board

[JDRBoston]

Thank you, jkorte. I can toggle the blue led but I am unable to fire the neopixel or toggle the red led on the Adafruit nRF52840 express. Below is my script and I've attached the pin mappings for the board. Do you have suggestions? Should I more this to a new discussion? J

# Test NeoPixel illumination on Adafruit nRF52840 Express Feather
#  running v1.24.0-preview.51.g91717a4f9.dirty

from machine import Pin
from neopixel import NeoPixel
import time

# ESP8226-style
#  docs.micropython.org/en/latest/esp8266/tutorial/neopixel.html
pixel = NeoPixel(Pin(16, Pin.OUT), 1)

pixel[0] = (255, 0, 0)
pixel.write()

# latest style
#  docs.micropython.org/en/latest/library/neopixel.html#output-methods
#  bbp is 3 for RGB LEDs
#  timing is 1 for 800kHz LEDs
pixel1 = NeoPixel(Pin(16, Pin.OUT), bpp=3, timing=1)

pixel1[0] = (255, 0, 0)
pixel1.write()

# Result: No illumination

#  timing is 1 for 400kHz LEDs
pixel2 = NeoPixel(Pin(16, Pin.OUT), 3, 0)

pixel2[0] = (255, 0, 0)
pixel2.write()

# Result: No illumination

# Test Blue LED illumination
#  Pin 42 / P1.10

blue_led = Pin(42, Pin.OUT)
blue_led.value(1)
time.sleep(4)
blue_led.value(0)

# Result: blue led illuminates

# Test Red LED illumination
#  Pin 47 / P1.15

red_led = Pin(47, Pin.OUT)
red_led.value(1)
time.sleep(4)
red_led.value(0)

# Result: ValueError: not a valid pin identifier

Adafruit Feather nRF52840 express pins.pdf

[jkorte-dev]

from neopixel import NeoPixel
from machine import Pin

p = Pin(16) # or Pin.board.P0_16
np = NeoPixel(p, 1)
np[0] = (255,0,0)
np.write()

is correct and the way I tested it (timing (400, 850, 800, 450)). I have no idea why it does not work. I checked the schematic of your board and it shows a WS2812B on Pin 16 (P0_16). Maybe the neopixel on your board uses different timings, but that is unlikely. I tested four different neopixel leds and the all showed slightly different timing tolerances. Some were labeled as WS2812B others as WS2812, but they all worked after tweaking the timing.

That your script fails to initialize Pin 47 (P1_15) is strange because it is defined. You can have a look at the defined pins with

help(Pin.board) .

is must show P0_16 -- Pin(16, mode=IN, pull=PULL_DISABLED) and P1_15 -- Pin(47, mode=IN, pull=PULL_DISABLED) among other Pins

Did you use the latest build? os.uname() should show:
(sysname='nrf52', nodename='nrf52', release='1.24.0-preview', version='v1.24.0-preview.84.g788c2082a.dirty on 2024-07-29', machine='SuperMini / Nice!Nano / Pro Micro nRF52840 with NRF52840')