UARTE with HW flow control RTS stays high

RE: UARTE with HW flow control RTS stays high

Håkon Alseth — Fri, 30 Jun 2023 07:49:26 GMT

Hi,

[quote user="Ray Ma"]The setup is to receive ~100 bytes, I tried manually sending from the other side but it's blocked b/c CTS(Nrf RTS) is high.[/quote]

How many bytes do you set to receive?

You mention that your code is similar to the snippet, but that snippet is effectively from app_uart_fifo.c.

app_uart_fifo will setup RX on one byte, and if you know how many bytes you will receive each time, I would strongly recommend that you use the nrfx_uarte directly instead, to get better control over the transport (ie. set the RXD DMA length).

If your application sets up one byte RX via nrf_drv_uart_rx(...), then it is approx. 22 us per byte in 460k8 baud, which will cause a timing error.

Kind regards,

Håkon

RE: UARTE with HW flow control RTS stays high

Ray Ma — Thu, 29 Jun 2023 16:46:15 GMT

Hi Hakon,

The setup is to receive ~100 bytes, I tried manually sending from the other side but it's blocked b/c CTS(Nrf RTS) is high.

I added 20us in the UART ISR to slow down the RX path and this also happens when I tune up the UART bps to 460800. It seems like I am only getting the ISR event for the first two bytes, is the ISR triggered per byte received?

Thanks,

-Rui

RE: UARTE with HW flow control RTS stays high

Håkon Alseth — Thu, 29 Jun 2023 14:58:33 GMT

Hi,

[quote user=""] I tried to add delay in the UART ISR event handler to slow down the receiving, what I see now is that RTS stuck in high, from device log I see in SW we only received 2bytes, from logic analyzer I see there were 5 bytes transferred before RTS goes high. RTS never goes back low after this so RX is broken, any idea why this is happening? [/quote]

How many bytes are setup to receive?

How long is the delay that you've added? The _ENDRX event is cleared before the callback handler is called in the driver itself, so I would assume that you get the callback twice.

Kind regards,

Håkon