Zephyr NCS 2.0.2 UARTE - TX works, RX does not

[Marcel]

Im struggling here with porting my code from SDK15 to NCS 2.0.2

Im happily TXing data from NRF52811 via UARTE and receiving via FTDI to PC, but Im unable to receive any data to the uC. I have tried both - the event based initialization of the uart and non-event based, but in both cases I can see the data being transmitted from PC to uC (uing Saleae) with correct voltage levels etc, but the data are never received by the uC. The pins are correct (I can see that they are correct by testing TX on the RX pin). The config of the line follows: 

CONFIG_LOG=y
CONFIG_SERIAL=y
CONFIG_LOG_PRINTK=y
CONFIG_PRINTK=y
CONFIG_UART_CONSOLE=n
CONFIG_USE_SEGGER_RTT=y
CONFIG_CONSOLE=y
CONFIG_RTT_CONSOLE=y
CONFIG_LOG_BACKEND_RTT=y
CONFIG_CBPRINTF_FP_SUPPORT=y

CONFIG_LOG_MODE_IMMEDIATE=y

# CONFIG_LOG_MODE_DEFERRED=y
# CONFIG_LOG_MODE_OVERFLOW=y

CONFIG_NRFX_GPIOTE=y
CONFIG_NRFX_UARTE0=y
CONFIG_NRFX_TWIM0=y
CONFIG_NRFX_SPIM0=y

#CONFIG_UART_INTERRUPT_DRIVEN=y

static void uarte_evt_handler(nrfx_uarte_event_t const * p_event,
                              void *                     p_context) {
    nrf_gpio_pin_toggle(LED_PIN);
    LOG_INF("uarte_evt_handler");
    if (p_event->type == NRFX_UARTE_EVT_TX_DONE) {
      LOG_INF("NRFX_UARTE_EVT_TX_DONE");
    } else if (p_event->type == NRFX_UARTE_EVT_RX_DONE) {
      while (1) {
        LOG_INF("NRFX_UARTE_EVT_RX_DONE");
      }
    } else if (p_event->type == NRFX_UARTE_EVT_ERROR) {
      LOG_ERR("NRFX_UARTE_EVT_ERROR");
    }
}

main() {  
  IRQ_CONNECT(DT_IRQN(DT_NODELABEL(uart0)), DT_IRQ(DT_NODELABEL(uart0), priority), nrfx_isr, nrfx_uarte_0_irq_handler, 0);
...
  static nrfx_uarte_t uarte_instance = NRFX_UARTE_INSTANCE(0);
  nrfx_uarte_config_t uarte_config = NRFX_UARTE_DEFAULT_CONFIG(UART_TX_PIN, UART_RX_PIN);
  uarte_config.baudrate = NRF_UARTE_BAUDRATE_38400;
...
  while(1) {
  k_sleep(K_SECONDS(1));
  retcode = nrfx_uarte_tx(&uarte_instance, (uint8_t *)tx_data_ok, sizeof(tx_data_ok));
   if (nrfx_uarte_rx_ready(&uarte_instance)) {
      while (1) {
        LOG_WRN("Getting byte waiting in UART RX buffer");
      }
...

I will never get to the "Getting byte waiting..." part. This is a example of the blocking code; in event based code I simply replace the callback with NULL in

nrfx_uarte_init() and uncomment CONFIG_UART_INTERRUPT_DRIVEN. The uarte_evt_handler() is never called in non-blocking code.

So to summarize - the above code TXses data every second, but never seems to receive any data from the RX pin. Physical connection is OK. I have tested this on two different boards with the same result. Sending data to the line using Python3 from Windows.

Any pointer to how to debug this appreciated. I might be missing something obvious here, but also not totally ruling out damaged pin.

[Simon]

Earlier I created a UART async sample based on the uart async test: https://github.com/simon-iversen/ncs_samples/tree/master/uart_async 

Check it out and see if you're able to receive data. If I remember correctly, NCS v1.9.0 was used.

Best regards,

Simon

[Marcel]

You example is based on Zephyr UART interface. Im trying to use the nrfx libs directly. 

I can confirm, that I can correctly use the Zephyr UART interface (ncs 2.0.2) and both the RX and TX lines are working correctly (using polling API). I, however, cannot make this work using nrfx uarte libs.

[Simon]

Ah, sorry. I was a little too quick to answer.

Check out the sample <ncs location>\zephyr\samples\boards\nrf\nrfx_prs\src\main.c, it uses the nrfx_uarte driver. The sample demonstrate how to switch between the SPIM2 and UARTE2 peripheral (same ID). Let me know if you get that sample to work or not, and if you need help to convert it to a pure UARTE sample.

Best regards,

Simon

[Marcel]

Thanks for the link. Can you elaborate a little more on the "switch between the SPIM2 and UARTE2 peripheral (same ID)" part? Is this something that might concern me in my application which uses UART and SPI peripheral on nrf52811 ? Im not sure what you are specifically referring to. Just a documentation pointer will do

[Simon]

Read nRF52811 Product Specification - Peripherals with shared ID for more information about this.

What it's saying is that you are not able to use all the UART(E), SPI(M), and TWI(M) modules at the same time because some of them share resources (registers). Hence you need to make sure that the peripheral base addresses to the modules that you chose to use do not overlap. 

See which peripherals are sharing ID in nRF52811 Product Specification - Memory - Instantiation

For example, in the instantiation page you can see that the peripherals TWIM0 and SPIM0 shares base address, so you cannot use them concurrently.

I think it should be fine for you to use UARTE0 and SPIM1 simultaneously, since they have different base addresses, respectively 0x40002000 and 0x40003000. The SPIM0 should also be fine to use concurrently with UARTE0 (and SPIM1), since it has the base address 0x40004000.

Best regards,

Simon