UART works on a custom board with nrf52840, but not on the nrf52840 DK

RE: UART works on a custom board with nrf52840, but not on the nrf52840 DK

Vidar Berg — Mon, 18 Oct 2021 07:42:24 GMT

Excellent, thanks for letting us know! I'm glad to hear that you found the problem.

Best regards,

Vidar

RE: UART works on a custom board with nrf52840, but not on the nrf52840 DK

alaa — Mon, 18 Oct 2021 07:40:19 GMT

Hi again Vidar,

Tx line is working fine, I was using wrong settings on the oscilloscope!

Thanks a lot for your support.

BR,

Alaa

RE: UART works on a custom board with nrf52840, but not on the nrf52840 DK

alaa — Mon, 18 Oct 2021 07:15:05 GMT

Hi Vidar,

HW flow control is off. I also checked both the maximum number of bytes in the transmit buffer and the number of bytes sent in the last transaction, both are always ''1''. Does that mean that everything is just working fine? I still can't see anything on the oscilloscope!

BR,

Alaa

RE: UART works on a custom board with nrf52840, but not on the nrf52840 DK

Vidar Berg — Fri, 15 Oct 2021 14:22:45 GMT

Hi Alaa,

Thanks for confirming, so we know the correct pin is selected at least. What about HW flow control, are you using it (is enabled in CONFIG)?

RE: UART works on a custom board with nrf52840, but not on the nrf52840 DK

alaa — Fri, 15 Oct 2021 13:46:15 GMT

Hi Vidar,

I'm using CLion.

Inrfjprog --memrd 0x4002850C returns 27, which is the expected value. (I'm using UART1)

BR,

Alaa

RE: UART works on a custom board with nrf52840, but not on the nrf52840 DK

Vidar Berg — Fri, 15 Oct 2021 13:08:33 GMT

Alaa,

Is probably fastest to just read it with nrfjprog from the command line if you are familiar with this tool.

Example: reading PSEL.TXD for UARTE0

$ nrfjprog --memrd 0x4000250C

You can also read the peripheral registers when debugging in VS code or Segger embedded Studio. Which IDE are you using?

Best regards,

Vidar

RE: UART works on a custom board with nrf52840, but not on the nrf52840 DK

alaa — Fri, 15 Oct 2021 12:44:54 GMT

Hi Vidar,

I'm new to the zephyr development environment, so I don't know what the best way to check the registers would be? I will look into that.

The application looks to be working fine, since I can probe the correct activity on the pin used for the modem power up control.

BR,

Alaa

RE: UART works on a custom board with nrf52840, but not on the nrf52840 DK

Vidar Berg — Fri, 15 Oct 2021 11:36:08 GMT

Hi,

Can you double-check that PSEL.TXD is set correctly? Also, does the application appear to function normally except for the missing UART transmissions?

Best regards,

Vidar

RE: UART works on a custom board with nrf52840, but not on the nrf52840 DK

alaa — Fri, 15 Oct 2021 11:11:32 GMT

Hi Vidar,

I just tried P0.27 for Tx and still nothing happens on it. "I'm using an oscilloscope to probe the line"

BR,

Alaa

RE: UART works on a custom board with nrf52840, but not on the nrf52840 DK

Vidar Berg — Fri, 15 Oct 2021 10:57:26 GMT

Hi Alaa,

Have you checked if the UART pins you use are available on the DK board and that they aren't routed to any buttons or LEDs (see silkscreen on the backside)? P0.26 and P0.27 are normally available.

Best regards,

Vidar