UART communication between two boards

[DeveloperZ]

Hi,

I am trying to establish UART communication between two nRF52 Dev boards. I flashed both of them with UART peripheral example from 15.2.0 SDK and connected TX,RX and GND pins.

Here, I encountered a weird issue where the two way communication(two terminals are recording the data when I enter data on any one terminal) is taking place with only one connection (TX from one board to RX on another / Connecting RX of both connectors) and nothing is being displayed on terminals when TX on both boards are connected. Can anyone explain this?

Thank you.

[Joakim Jakobsen]

Hi.

I'm not sure if I understand exactly what your setup looks like.

You have only connected TX from one board to RX on another board, and are able to acheive two way communication? You also get two way communication connecting only RX from one board to RX on the other board?

If you have two DK's (Board A and Board B),
You should connect TX from board A to RX on board B and TX from board B to RX on board A.

Could you provide some more information as well?
Which SDK are you working with? nRF52 DK? Custom board? etc. 

Best regards,
Joakim

[DeveloperZ]

Hi,

Joakim Jakobsen said:

You have only connected TX from one board to RX on another board, and are able to acheive two way communication? You also get two way communication connecting only RX from one board to RX on the other board?

Yes, this is what I was facing. I was on vacation and just returned today. So, didn't have much time working on this.

Joakim Jakobsen said:

If you have two DK's (Board A and Board B),
You should connect TX from board A to RX on board B and TX from board B to RX on board A.

This is what I have started with. Few weeks ago, it was working perfect with these connections but later it started to behave weirdly where the two way communication was occurring with only one connection. 

I am working with 15.2.0 SDK, examples-> peripheral->uart. I didn't create any custom board. I am using pca10040.h file only. And yes, I am using nRF52 DK's with nRF52832.

Thank you.

[DeveloperZ]

Joakim Jakobsen said:

Is all the data you sent from one board to the other, entered into the terminal?

Yes, I have been sending data only through the terminals.

Joakim Jakobsen said:

Have you tried sending any data directly through the application?

No, I haven't tried that yet.

[Joakim Jakobsen]

DeveloperZ said:

No, I haven't tried that yet.

 Maybe you could try that, and see if you still get a two way com. sending the data through the application.

Regards.

[DeveloperZ]

Joakim Jakobsen said:

sending the data through the application.

This doesn't show the two way communication between the boards.

[DeveloperZ]

Can I know why is the two way communication happening when sending the data using terminal and why not when the data is being transferred over the application?

Thank you.

[Joakim Jakobsen]

Hi.

You are seeing this behaviour because of how the DK's are connected.

The data being entered in the terminal will be forwarded via the segger chip on the DK to the nRF chip.
Because you have connected both RX pins, both the nRF's will receive the data.
When the UART application receives the data, it will process it and print the data. This is done by the nRF forwarding the data to your terminal via the segger chip and the TX line.

That is why you are seeing the two way comunication. If you connect TX1 -> RX2 and TX2 ->RX1, you should see the data go into an endless loop between the two.

Best regards,
Joakim.