Direct Test Mode v2.4.1 GUI does not work with third party boards

[lx_brz]

Using nRF Connect for Desktop on Ubuntu 24.04 LTS I am trying to use the Direct Test Mode v2.4.1 software with our own custom board.

On https://docs.nordicsemi.com/bundle/nrf-connect-direct-test-mode/page/index.html you wrote:

> The application also supports third-party devices that are programmed with the DTM standard protocol and expose access to it through a serial port.

But it is not possible. Trying to select the FTDI based UART and running clicking "Start test" I see the following error:

At the same time I am connected to the board via RTT to view logs and don't see any communication.

On the contrast when I use cutecom to send commands as hex codes directly, everything works as expected:

And I see the expected communication activity on the RTT logs:

Help would be much appreciated. It would be much more convenient to use your GUI based Direct Test Mode tool instead of sending and decoding the DTM commands as hex manually.

There are no problems by the way using a nrf52840DK. It only does not work with the custom board, connected via UART, although you explicitly write:

> The application also supports third-party devices that are programmed with the DTM standard protocol and expose access to it through a serial port.

Thanks

Alex

[Elfving]

lx_brz said:

Not sure what exactly you mean with "any DTM fw", but I have programmed the custom board with this sample: docs.nordicsemi.com/.../README.html

Great. DTM is a program defined by BT SIG, so there are multiple versions of this that I guess should act the same. Though if you maybe ran something like radio test, (which is similar to DTM, just better) the DTM app wouldn't work. 

lx_brz said:

There is no programmer attached, only the serial connection, so there is no point in trying to press that button.

I see. Well then I think that is the problem. DTM needs a COM port for it to work. Could you connect your DK to your third party board using a JTAG 10pin debug connector, and try the same thing again? You hopefully have support for that on your board. 

Regards,

Elfving

[lx_brz]

Elfving said:

Great. DTM is a program defined by BT SIG, so there are multiple versions of this that I guess should act the same.

I understand that. By the way: nordic has implemented some vendor specific extensions to the standardized "direct test mode" like constant carrier, see https://github.com/nrfconnect/sdk-nrf/blob/main/samples/bluetooth/direct_test_mode/src/dtm.c#L169

Elfving said:

I see. Well then I think that is the problem. DTM needs a COM port for it to work. Could you connect your DK to your third party board using a JTAG 10pin debug connector, and try the same thing again?

What would be the point of doing that? The DTM app can not possibly know which pins it must configure for UART on our custom board. So if I just click "program" and it flashes the same firmware as for the nrf52840DK, the chances are high that it will not work and will also stop working with the third party program I mentioned above, because probably our custom board does not use the same pins for UART communication as the nrf52840DK.

Also the serial port or "COM port" as you refer to it is available and functional, as the third party application demonstrates.

Sorry, I don't understand how this is supposed to help, maybe there is a misunderstanding somewhere?

[Elfving]

lx_brz said:

Sorry, I don't understand how this is supposed to help, maybe there is a misunderstanding somewhere?

Yeah sorry about that. As well as for how long it took for you to get a reply here. I guess I meant uart.

Flash DTM to your custom board. Then you can for instance connect the uart pins of the nrf52840DK you have, to whichever uart pins you use on your custom board. I just tried this myself with two '840DKs and it worked fine. 

Just erase the nRF on the DK (with eg. nrfjprog --recover) to make sure that you are communicating with the correct nRF. The DTM app might prompt you to reflash the DK, but you can just decline that and it should still work.

Regards,

Elfving

[lx_brz]

Elfving said:

Yeah sorry about that. As well as for how long it took for you to get a reply here.

No worries and thank you for your reply. I have found the problem now. The nordic Direct Test Mode GUI application assumes a hard-coded baud rate of 19200. The firmware compiled for our custom board used 115200 though. That's why it didn't work. When compiling the sample with a baud rate of 19200 the Direct Test Mode GUI can be used without a problem.

I only noticed that the original baud rate in the sample was 19200 when I compiled it myself. I received the DTM firmware with 115200 setting from a colleague. That also explains why it worked in the third party tool, since the third party tool allows to set the correct baud rate.

Thank you for your support, the ticket can be marked resolved.