nRF5340DK VCOM only works with putty

[ubat]

Hey guys,

an issue I was postponing but need to solve for an upcoming management demonstration: I can only connect to the nRF5340DK VCOM with putty.

Using Hterm or the Matlab serial port functionality, which is what I need for the demo, will shut down the Jlink cpu. LED5 will turn off, and the Jlink CDC UART port disappears from the device manager.

I tried DTR/RTS pins on and off, to no avail. This solved the problem here nRF52 DK - USB CDC ACM Example not working with HTerm/Qt - Nordic Q&A - Nordic DevZone - Nordic DevZone (nordicsemi.com) e.g., which is similar I guess.

The Jlink cpu seems to reset upon Hterm or Matlab serial connecting. The nRF5340 is still up and going, as indicated by LEDs signaling new received packets.

Any idea?

Thank you,

Uli

[Øyvind]

Hello Uli, 

Can you provide more information on what version of the nRF5340DK you are running and with what application? I will try to replicate here. That said, the JLink CPU should not be affected when connecting via Serial, Do you see 2 serial ports from the device?

Kind regards,
Øyvind

[ubat]

Hi Øyvind,

I'm using version 2.0.0, PCA10095, 2021.42, 1050083097 and two others.

I can see two serial ports from the device; I'm currently using only the network CPU, so only trying to use VCOM0.

One of the freeware applications would be HTerm - der-hammer.

Thank you!

Uli

[ubat]

Thank you for reproducing! No special settings on the board for me, nothing connected. I guess I'll have to try another USB port, or another computer for that matter.

[Øyvind]

Yes, please do, and let me know if you are still not able to get it working. 

[ubat]

Hey Øyvind,

now that's silly - other USB ports are working, and so is the previous USB hub, if I'm adding an external power supply.

So HTerm and Matlab caused power issues when connecting the serial port, while Putty and the Visual Studio Code terminal didn't. And the nRF CPU was always up and going; only the IF CPU was down. An interesting failure mode :D

Anyway! Very glad it's working. Thank you!

[ubat]

One last addition:

HTerm still only works when the utilization of the UART is low; about 10% total currently is working fine, 40% is not.

Again, HTerm ist shutting the IF CPU is down in that case.

Let's see if I manage to cope with that. Something's really strange here.

[ubat]

Too bad - though Hterm is working now, it's still not working with Matlab. So the USB port has got an influence, but even more so the application. The IF CPU will go into a mode where it also cannot be flashed. Sometimes this state even persists through a hard power toggle.

Fortunately hub4com in combination with com0com is also working now, and I can forward the data to a virtual port. The virtual port and Matalb are working :)

[Øyvind]

ubat said:

Fortunately hub4com in combination with com0com is also working now, and I can forward the data to a virtual port. The virtual port and Matalb are working :)

Happy to hear you found a work-around.

ubat said:

The IF CPU will go into a mode where it also cannot be flashed

Can you please please elaborate? Does the device show when you issue nrfjprog --ids ?