Problem communicating via UART in non-blocking mode with higher baud rates

[Akhil Bhargav Josyabhatla]

Hi,

I am trying to communicate with a Wi-Fi module external to nRF52840 via UART. I am using the nrf_serial_read() API. I have tried different values for UART baud rate from 115200 to 921600 but nothing works in the non-blocking mode(timeout_ms = 0).

The only working combinations between 115200 and 921600 are:
Baud rate                   Timeout         

115200                      125ms
230400                      100ms

Q1) Is the timeout necessary to make the UART communication work with a high baud rate?

Q2) I need to achieve a baud rate of 921600 for a smoother application with a minimum timeout in ms. Is there a way to achieve it? 

Thanks,
Akhil

[MartinBL]

Hi,

 

1. How does it not work? 
2. Do you check the return code of nrf_serial_read()?
3. Does it return an error? 
4. Do you have a logic analyzer?

I don't think the timeout should matter. Note though, that you won't achieve 921600 exactly, but 941176,a so you are likely to get framing errors which can be problematic. 

 

 

[Akhil Bhargav Josyabhatla]

Hi MartinBL, 

I got the nrf_serial_read working. I see that the communication is successful but I get framing errors and cannot receive complete data even with 115200 baud rate at timeout = 0.
Same is the case with all other baud rates till 921600. 

But, for baud rate 115200, I see reliable communication without any framing error for timeout = 125ms. 

I guess you're right, the timeout shouldn't matter but the timeout is playing some role here and I am confused about that.

[MartinBL]

Hi,

What kind of WiFi module is this?

Do you have a logic analyzer or an oscilloscope so we can see what goes on on the TX and RX lines?

[Akhil Bhargav Josyabhatla]

I am using Zentri AMW007, a stand-alone Wi-Fi networking module. 

I do have an oscilloscope with me. Yes, I'll try scoping the TX, RX.

[Akhil Bhargav Josyabhatla]

Hi Martin, 
We have scoped the TX and RX and are able to see good signal flow over the lines. 

What do you think could be a possible reason causing this problem? Any thoughts? 

[MartinBL]

It sounds strange. 

1. This is a two way communication right?
2. How do you set the baud rate used by the AMW007? Are you sure that both devices use the same baud rate?
3. Do you have a link to some datasheet detailing how you configure the baud rate on the AMW007?
4. Maybe the AMW007 is slow to respond and that is why you need a timeout? 
5. Can  you show me more of the code you use to read and write data?