UART stop bit is shorter than data bit

RE: UART stop bit is shorter than data bit

Thomas U — Thu, 23 May 2024 14:17:47 GMT

Hi Einar,

I'm happy to report that nrf_drv_uart_tx() works perfectly. Thank you for your help!

RE: UART stop bit is shorter than data bit

Einar Thorsrud — Wed, 22 May 2024 14:38:44 GMT

Hi,

An update from me. I have not got to the bottom of the root cause here, but when using app_uart_put() you are sending each byte as a separate transaction. And it seems that for some reason the new transactino is started before the stop bit has finished (you see the whole start bit). If you instead of sending single bytes send all data in one transaction using nrf_drv_uart_tx() or similar, that seems to resolve the issue (the added benefit is that it is more efficient).

RE: UART stop bit is shorter than data bit

Einar Thorsrud — Wed, 22 May 2024 13:52:13 GMT

Hi,

I see the same at low baud rates. Here is with your code on a DK (9600 baud):

For comparison, here is with the code except that the baud rate is 115200:

I am not able to explain this yet though, but I am looking into it and will get back to you.

RE: UART stop bit is shorter than data bit

Thomas U — Wed, 22 May 2024 12:01:27 GMT

Hi Nordic people,

I wanted to inform you that I am attempting to use the UARTE1 instance, following the advice provided in Case ID: 327213.

This has led me to configure the sdk_config.h file with the following settings:

#define APP_UART_DRIVER_INSTANCE 1

#define UART1_ENABLED 1

#define NRFX_UARTE0_ENABLED 1

#define NRFX_UARTE1_ENABLED 1

RE: UART stop bit is shorter than data bit

hmolesworth — Tue, 21 May 2024 18:38:19 GMT

Quick fix while Nordic investigates: Use 2 stop bits in CONFIG instead of default 1 stop bit; search for the definition of UARTE struct to get the magic defines. This (should) only affect transmit, not receive. Don't see stop bits in def,, might have to post-write

C RW STOP Stop bits:

One 0 One stop bit
Two 1 Two stop bits

NRF_UARTE0->CONFIG = (UART_CONFIG_STOP_Two << UART_CONFIG_STOP_Pos) | (UART_CONFIG_HWFC_Disabled << UART_CONFIG_HWFC_Pos) | (UART_CONFIG_PARITY_Excluded << UART_CONFIG_PARITY_Pos);