nRF5340-DK VCOM CTS line remains high

[Adrian Eggenberger]

Hi

I'm trying to make the UART-HCI example run on my nRF5340-DK board.

Environment:
- nRF5340-DK Version 2.0.0 (2022.13)
- nRFConnect 2.7.0

I've built the example with VS Code and downloaded it to the Network Core. On the Applicaiton Core the empty app example is installed.

When I now send a HCI command over the VCOM to nRF5340 the communication seems to work (I've seen the data reception in the debugger). The data sent back from the nRF5340 over VCOM is not received on the VCOM.

Both VCOM variants have been tried. In both cases I see the same behavior. At the moment I've configured the following pins to be used for the UART:
P0.19 - RTS
P0.20 - TXD
P0.21 - CTS
P0.22 - RXD.

A look at the signals with a signal analyzer shows that the P0.21 (= CTS) is constantly high. If I'm right this blocks the transmit from the nRF5340. What causes the VCOM chip to block the transmit?

Regards Adrian

[Simonr]

Hi

Sorry about the very late reply here, but this seems to have fallen through the cracks on our end. Just to make sure here, you are using the interface MCU chip for the UART and already existing VCOM on the nRF5340 DK, correct?

If so, can you share some details on how you're measuring the pins high/low here, and where in the code the application is at this point? If it is currently transmitting from the interface chip to the nRF5340, it makes sense that the CTS pin is high so it doesn't send data while it is receiving for example.

Because if you're planning on using these pins for UART yourself on the pin outputs you need to cut solder bridges SB27, SB28, SB29 and SB30 to use these pins for other purposes.

Best regards,

Simon