nrf51 flashing

[gaalb]

Dear Bitcraze team!

I'd like to attach a u.FL antenna to my crazyflie 2.1. I've read here, that in order to make the crazyflie use this antenna instead of the chip antenna, I need to modify and re-compile the firmware of the nrf51 chip.
To this end, I cloned the latest version of the nrf51 firmware, and after installing the arm-none-eabi toolchain, I could compile the firmware like so:

aimotion-i9@aimotioni9-MS-7D25:~/Projects/crazyflie2-nrf-firmware$ make PLATFORM=cf2 BLE=0
Generating version.h
python3 tools/build/generateVersionHeader.py --crazyflie-base /home/aimotion-i9/Projects/crazyflie2-nrf-firmware --output _build/version.h
/home/aimotion-i9/Projects/crazyflie2-nrf-firmware
Compiling file: main.c
Linking target: _build/cf2_nrf.out

   text	   data	    bss	    dec	    hex	filename
  24844	    164	   4584	  29592	   7398	_build/cf2_nrf.out

Preparing: _build/cf2_nrf.hex
Preparing: _build/cf2_nrf.bin
BLE  Disabled
Built for platform cf2

I flashed this firmware to my crazyflie 2.1 via crazyradio, and it appears to go through fine:

aimotion-i9@aimotioni9-MS-7D25:~/Projects/crazyflie2-nrf-firmware$ make cload
Generating version.h
python3 tools/build/generateVersionHeader.py --crazyflie-base /home/aimotion-i9/Projects/crazyflie2-nrf-firmware --output _build/version.h
/home/aimotion-i9/Projects/crazyflie2-nrf-firmware
Compiling file: main.c
Linking target: _build/cf2_nrf.out

   text	   data	    bss	    dec	    hex	filename
  46012	    256	   6272	  52540	   cd3c	_build/cf2_nrf.out

Preparing: _build/cf2_nrf.bin
python3 -m cfloader flash _build/cf2_nrf.bin nrf51-fw
Restart the Crazyflie you want to bootload in the next
 10 seconds ...
Flashing 1 of 1 to nrf51 (fw): 46267 bytes (46 pages) .1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1.1

However, after the flashing is over, the drone's M2 blue light stays on, solid without blinking. The drone cannot be turned off via the on/off button, only via unplugging the battery. It cannot connect to my computer using a crazyradio, although I can put it into bootloader mode again by long pressing the on/off button. In order to make it usable again, I need to do a cold boot recovery. Regarding the solid blue light, I read here, that this may indicate corrupted nrf51 firmware, but I'm not sure where it could've got corrupted, as I haven't yet modified anything about the firmware, and used the latest version.
In addition, in order to root out the issue, I tried to build with the bluetooth enabled, and/or flash with the following command, but had the same result:

python3 -m cfloader flash cf2_nrf.bin nrf51-fw

Could you provide some pointers on achieving my goal of using an external u.FL antenna, and compiling/flashing firmware to the nrf51 over crazyradio?

Thanks a lot for your help!
Botond Gaál

[gemenerik]

Have you already attached the antenna, or is this happening with a completely stock Crazyflie—radio, antenna, and firmware (both STM and NRF) unchanged?

It looks like the firmware flashed fully. Does the drone restart normally, or does it go straight into the solid blue LED state? No red blinking bursts indicating an assert?

[gaalb]

This happens whether the antenna is attached or not. I first wanted to make sure I can compile and flash the stock firmware before making any modifications.
The drone does not restart after the flash (or at least I don't think it does, it surely doesn't spin each propeller to imitate a tune). It goes straight into the solid blue LED state, no red blinking.