How is the RTS-pin controlled in UART with flowcontrol

RE: How is the RTS-pin controlled in UART with flowcontrol

Nicolai Kildegaard — Mon, 17 Apr 2017 09:34:55 GMT

static const app_uart_comm_params_t comm_params = { GSM_RX_PIN_NUMBER, GSM_TX_PIN_NUMBER, GSM_RTS_PIN_NUMBER, GSM_CTS_PIN_NUMBER, GSM_UART_FLOW_CONTROL, GSM_USE_PARITY, GSM_UART_BAUDRATE };

void uart_evt_callback(app_uart_evt_t * uart_evt) { if (uart_evt->evt_type == APP_UART_DATA_READY) uint8_t cr; while(app_uart_get(&cr) == NRF_SUCCESS) { //cr should now contain the data } } }

uint32_t gsm_uart_init(void) { return APP_UART_FIFO_INIT(&comm_params, GSM_UART_RX_BUF_SIZE, GSM_UART_TX_BUF_SIZE, uart_evt_callback, GSM_UART_PRIORITY, error_code); }

RE: How is the RTS-pin controlled in UART with flowcontrol

Nicolai Kildegaard — Mon, 17 Apr 2017 09:34:46 GMT

This is a very old question. I don't have access to the code in the form it was in back then, and now it looks completely different.

But I didn't do anything different from the example projects. My problem back then was that I was setting break points elsewhere in the code, and that blocked the uart connection from operating as I expected.

I will add a comment with what I can salvage from back then and fit in a comment, but I can't guarantee it will work.

RE: How is the RTS-pin controlled in UART with flowcontrol

Khalid — Sat, 15 Apr 2017 17:32:35 GMT

hello Nicolai would you mind sharing your code because im doing a similar thing with my nrf and i am running to all kinds of issues

thank you

RE: How is the RTS-pin controlled in UART with flowcontrol

RK — Thu, 19 Nov 2015 01:43:48 GMT

"I know the pin is supposed to be set when the softdevice does something"

Not directly - the softdevice knows nothing at all about whether you are using the UART or not and doesn't do anything to the RTS signal. If you're thinking the softdevice disables UART by forcing the RTS pin high, when it's doing things, that is not correct.

The RTS pin goes high when the buffer space falls to a minimum to stop the sending device sending until you've read the data which already came in so you don't lose it. Are you reading the data which comes in?

RE: How is the RTS-pin controlled in UART with flowcontrol

atune — Wed, 18 Nov 2015 23:02:50 GMT

Legacy UART? Are you reading the rx fifo?

The UART receiver chain implements a FIFO capable of storing six incoming RXD bytes before data is overwritten ... When flow control is enabled, the UART will deactivate the RTS signal when there is only space for four more bytes in the receiver FIFO. .... The RTS signal will first be activated again when the FIFO has been emptied, that is, when all bytes in the FIFO have been read by the CPU, see Figure 3.

In your picture two bytes are received and RTS is set, just like described in the documentation.

RE: How is the RTS-pin controlled in UART with flowcontrol

Nicolai Kildegaard — Wed, 18 Nov 2015 15:57:45 GMT

No that was a typo. Sorry...

RE: How is the RTS-pin controlled in UART with flowcontrol

awneil — Wed, 18 Nov 2015 15:44:16 GMT

SPI ??