my st-link has a 3.3V pin that is only good for measuring but not delivering power/voltage. Maybe that is your problem? I had to use a pin on another connector.
edit: and my experience with st-link only includes stm32 chips. Maybe others can chime in…
@joba1 Well, I also tried it with USB connected to power, did not work.
Hm, I ordered some parts to make an adapter for my Blackmagic Probe… I will report back if this works
No, Blackmagic also does not work…
No, the standard that ships with Ubuntu 20.04. Will try the one you pointed to later, thanks!
This the below linked article from May 21 seems to say J-Link/ST-Link are not supported, that would be a shame if true. I miss the debugging. Have not tried it myself…
Paragraph 6:
Heltec uses a custom CubeCell bootloader for ASR650x where serial number/license is stored into flash to enable Arduino support. Due to implementation thereof it is unfortunately not possible to use the ARM SWD interface for firmware upload and debugging (with J-Link or ST-Link).
https://www.thethingsnetwork.org/forum/t/heltec-cubecell-part-2/37225
Well, you only have to pay attention not to overwrite row 3 of the user flash… or back it up before 
So, perhaps it is doable? That would be good to hear.
I’m researching it with a friend. It seems that timing after reset is important.
CubeCell does not support ST-LINK.
Yes, we found out. Which JTAG adapter would you recomend?
JTAG is not currently supported, we use kitProg3 (PSoC).
OK, thank you. But as I understand, KitProg also uses SWD as transport. I’ll report back as soon as I got my J-Link
Does Heltec have an “app developer guide to using a debugger with the Cubecell” sort of document?
Sorry, we currently do not have this type of document.
I’m using a kitgProg3 but I’m unable to communicate with a HTCC-AB01 board - anything special other than connecting SWD, SWC, RES, GND pins? The board is resetting while trying to connect - but the acquistion doesn’t happen with PSoC Programmer. Ping @shaffer?
You are not connected to the power supply.
The CubeCell board is powered via USB adapter, the kitprog3 programmer connected to the CubeCell as described above.
You should use the 3.3V of kitgProg3 to power the CubeCell.
Anybody can run debugger with cubecell?