Flash nRF52840 via USBD virtual COM port

[Ethan Fischer]

Hello, I have an Adafruit nRF52840 Feather Express, and I'd like to be able to flash the micro through the USB virtual COM port because it has to go in a case and the SEGGER 10 pin connector will not fit. I also need BLE (specifically buttonless DFU) working as well, so to start I've gotten the usbd_ble_uart_pca10056_s140 example from nRF5_SDK_17.1.0 flashed and working on the micro. This is a good start, I can connect to it via bluetooth using the nrf connect app and it shows up as a COM port device on my WIndows 11 computer. I'll have to stitch in the buttonless DFU stuff, but right now I want to figure out how to flash the micro through the USB virtual COM port. Right now, when I open up the nRF Connect for Desktop (v5.0.0) Programmer app (v4.3.0), the micro shows up as nRF52 USB CDC BLE Demo but after selecting the micro I get an orange caution message that reads "No operation possible. If the device is a MCUboot device make sure it is in the bootloader mode or enable MCUboot."  I use Segger Embedded Studio v8.12, and I can't find a way to flash the micro via a COM port, SES appears to require a J-Link programmer.

[Hieu]

Hi Ethan,

You cannot flash the device in the sense of accessing the entire flash memory and write at any address you want.

What you can do is setting up a bootloader that allows updating the application via USBD. The Secure Bootloader in the nRF5 SDK supports that.

The reason the nRF Connect for Desktop - Programmer app gives you an error is because it is intended to talk with the bootloader in DFU mode, not usbd_ble_uart_pca10056_s140.

Please refer to the Bootloader/DFU documentation for more information: https://infocenter.nordicsemi.com/topic/sdk_nrf5_v17.1.0/lib_bootloader_modules.html 

Please also remember that to get the bootloader onto the device, you still need to first do so by the debugger interface.

Hieu

[Ethan Fischer]

Ok I gotcha, so then is it possible to use the USB bootloader and the BLE bootloader in one? Would be nice to be able to update the firmware via USB or BLE.

[Hieu]

Yes, using enable both USB and BLE transport for DFU is possible. You could also refer to this case:  Secure DFU with both BLE + USB transport .