A Post For Posterity and a PSA: How To Not Go Down A Rabbit Hole When the PCA10056 (aka nRF52840 Dongle) Will Not Program w/nRF Connect for Desktop (currently circa v3.10.0) (BLE App)

[johnwest]

Hello All,

First, thanks for this post:  https://devzone.nordicsemi.com/f/nordic-q-a/40924/how-can-i-restore-the-original-bootloader-of-a-pca10059 ; I'm attaching the file here again JIC.

7242.pca10059_bootloader_mbr_v1.0.1.hex

And, in case anyone else thinks they've bricked their nRF52840 dongle when all looks well trying to load the Bluetooth Low Energy scanner and getting the 'can't open serial port error':

Apparently, if the virtual com port opened is greater than 15??? (Not verified - but == 20 -> fails) - you'll need to remap it under device manager to be ideally less than 10.
After reading a lot of posts; including one that said the dongle was 'bricked' (and after putting the programming header on it) - I tried reducing the com port from 20 to 6 and it worked.  

So, apparently, nRF Connect for Desktop (currently circa v3.10.0 at the time of this writing) can't handle a com port setting of 20 or greater when programming the nRF52840 dongle - just like when this bug was originally seen on PC's +20 years ago when com ports > 9 were first possible under the host operating system.

Regards,
johnwest

[Susheel Nuguru]

Thanks for this report John, I will talk to the nRF Connect for Desktop team to confirm this and will come back and report here.

[mrono]

johnwest said:

So, apparently, nRF Connect for Desktop (currently circa v3.10.0 at the time of this writing) can't handle a com port setting of 20 or greater when programming the nRF52840 dongle

I had to try this since the dongle I use daily on my development PC is precisely on COM20. I don't reprogram it often, but surely have done so at least occasionally in the past.

I let the RSSI viewer app reprogram the dongle, verified that it works, and then used the BLE app to put the connectivity firmware back. It did work, though I needed to unplug the dongle after programming the RSSI firmware. So I don't think large com port numbers are categorically broken. Perhaps there is some weakness in the update process and remapping to a new port gives you a clean restart?