Serial UARTE Rx fails with continuous timeout error

[Manjunath S]

Hi,

I have a custom board with nrf52840 with UARTE1 instance enabled for RS485 communication.

I have 2 boards on the same configuration and trying to send data to each other.

below is the UARTE instance used

NRF_SERIAL_DRV_UART_CONFIG_DEF(m_uarte1_drv_config,
                      24, 25,
                      RTS_PIN_NUMBER, CTS_PIN_NUMBER,
                      NRF_UART_HWFC_DISABLED, NRF_UART_PARITY_EXCLUDED,
                      NRF_UART_BAUDRATE_115200,
                      UART_DEFAULT_CONFIG_IRQ_PRIORITY);

NRF_SERIAL_QUEUES_DEF(serial1_queues, SERIAL_FIFO_TX_SIZE, SERIAL_FIFO_RX_SIZE);
NRF_SERIAL_BUFFERS_DEF(serial1_buffs, SERIAL_BUFF_TX_SIZE, SERIAL_BUFF_RX_SIZE);
NRF_SERIAL_CONFIG_DEF(serial1_config, NRF_SERIAL_MODE_DMA,
                      &serial1_queues, &serial1_buffs, NULL, sleep_handler);
NRF_SERIAL_UART_DEF(serial1_uarte, 1);                      

Serial UARTE is initialized with the above configurations.

The problem is after sometimes randomly, the device gives me continuous timeout error when I try to read data.

But it is transmitting data I can confirm this because the other device is able to receive the data sent. 

Once it goes into this mode, the only way to come out is either a restart or a re-init of serial UARTE. If I re-init, it works for some more time and again goes back to this mode randomly.

could anyone please guide me in the right direction to fix this.

PS: I am also using a direction pin (pin no 40) which I CLEAR to Rx data and SET to Tx data.

[Manjunath S]

Susheel Nuguru said:

HFCLK

Hi,

We are using the internal clock for this communication. and the baud rates are set as per the code above.

I am using nrf_serial_write() and nrf_serial_read() functions to write and read. I am not aware of the HFCLK you are mentioning. Could you please let me know where it needs to be set/configured?

[Susheel Nuguru]

If your application needs a high precision clock (better than internal RC oscillator) Then you need to have XTAL HFCLK on your PCB connected to nRF which can be started using the clock module using the API nrf_drv_clock_hfclk_request. If you have this enabled on both peer and your device, there is better accuracy of the clocks on UART and hence less probability of of clocks jittering causing framing errors.