UART stop-bit pulse time is not fit to baudrate.

[Ethan.jskim]

Dear expert.

I found something strange thing in UART operation

one of our product is developed based on the NUS example in nRF5_SDK using nRF52833

In low speed baudrate(under 115200bps) settings, all uart pulses are same duration

but in high speed baudrate(from 115200bps and over), stopbit pulse time is different with other bits pulse every data.

Below image is captured signal by analyzer in each baudrate and can find delta-time(p0: normal bits time, P1: stopbit time)

In test sequence, nRF52833 send TX response "+OK\r" if received "AT\r"

capture image shows stopbit pulse keep 57kHz even though over 57600bps baudrate

I don't know why stopbit pulse shows strange symtom in high speed baudrate

let me know what am I should check.

BR.
Ethan

[Sigurd]

Hi!

printf is using app_uart_put(), so if you are using e.g. both nrf_drv_uart_tx() API directly and printf(), you might get some conflict.

The nRF52833 has 2 UARTE instances, so one option is to e.g. use e.g. UARTE1 for your nrf_drv_uart_tx() , and let app_uart use UARTE0

[Ethan.jskim]

thank you Sigurd.

I understood and I will try other UARTx for active debugging.

I will close this ticket.