Getting lots of noise/errors using Serial library.

[jfarjona]

Hi,

I am getting lots of transmission errors using the Serial library.   I changed the Serial_Uartes example by removing the serial1 interface and creating a simple loopback at 115,200 bps.

Just by holding a key on the keyboard on a screen serial connection creates lots of lost bits.  What could be the problem?

Below is the modified code for .../examples/peripherial/serial_uartes/main.c

(....)

#include "app_error.h"
#include "app_util.h"
#include "boards.h"

/** @file
 * @defgroup nrf_serial_uartes_example main.c
 * @{
 * @ingroup nrf_serial_uartes_example
 * @brief Example of @ref nrf_serial usage. Loopback example using two UARTE peripherals.
 *        Please short Arduino SCL and SDA GPIOs to start transmission.
 *
 */

#define OP_QUEUES_SIZE          3
#define APP_TIMER_PRESCALER     NRF_SERIAL_APP_TIMER_PRESCALER

static void sleep_handler(void)
{
    __WFE();
    __SEV();
    __WFE();
}

NRF_SERIAL_DRV_UART_CONFIG_DEF(m_uarte0_drv_config,
                      RX_PIN_NUMBER, TX_PIN_NUMBER,
                      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_DRV_UART_CONFIG_DEF(m_uarte1_drv_config,
                      ARDUINO_SDA_PIN, ARDUINO_SCL_PIN,
                      RTS_PIN_NUMBER, CTS_PIN_NUMBER,
                      NRF_UART_HWFC_DISABLED, NRF_UART_PARITY_EXCLUDED,
                      NRF_UART_BAUDRATE_115200,
                      UART_DEFAULT_CONFIG_IRQ_PRIORITY);


#define SERIAL_FIFO_TX_SIZE 256
#define SERIAL_FIFO_RX_SIZE 256

NRF_SERIAL_QUEUES_DEF(serial0_queues, SERIAL_FIFO_TX_SIZE, SERIAL_FIFO_RX_SIZE);
NRF_SERIAL_QUEUES_DEF(serial1_queues, SERIAL_FIFO_TX_SIZE, SERIAL_FIFO_RX_SIZE);


#define SERIAL_BUFF_TX_SIZE 1
#define SERIAL_BUFF_RX_SIZE 1

NRF_SERIAL_BUFFERS_DEF(serial0_buffs, SERIAL_BUFF_TX_SIZE, SERIAL_BUFF_RX_SIZE);
NRF_SERIAL_BUFFERS_DEF(serial1_buffs, SERIAL_BUFF_TX_SIZE, SERIAL_BUFF_RX_SIZE);


NRF_SERIAL_CONFIG_DEF(serial0_config, NRF_SERIAL_MODE_DMA,
                      &serial0_queues, &serial0_buffs, NULL, sleep_handler);
NRF_SERIAL_CONFIG_DEF(serial1_config, NRF_SERIAL_MODE_DMA,
                      &serial1_queues, &serial1_buffs, NULL, sleep_handler);


NRF_SERIAL_UART_DEF(serial0_uarte, 0);
NRF_SERIAL_UART_DEF(serial1_uarte, 1);


int main(void)
{
    ret_code_t ret;

    ret = nrf_drv_clock_init();
    APP_ERROR_CHECK(ret);
    ret = nrf_drv_power_init(NULL);
    APP_ERROR_CHECK(ret);

    nrf_drv_clock_lfclk_request(NULL);
    ret = app_timer_init();
    APP_ERROR_CHECK(ret);

    // Initialize LEDs and buttons.
    bsp_board_init(BSP_INIT_LEDS | BSP_INIT_BUTTONS);

    ret = nrf_serial_init(&serial0_uarte, &m_uarte0_drv_config, &serial0_config);
    APP_ERROR_CHECK(ret);

    // ret = nrf_serial_init(&serial1_uarte, &m_uarte1_drv_config, &serial1_config);
    // APP_ERROR_CHECK(ret);

    static char tx_message[] = "Hello nrf_serial!\n\r";

    ret = nrf_serial_write(&serial0_uarte,
                           tx_message,
                           strlen(tx_message),
                           NULL,
                           NRF_SERIAL_MAX_TIMEOUT);
    (void)nrf_serial_flush(&serial0_uarte, 0);

    while (true)
    {
        char c;
        ret = nrf_serial_read(&serial0_uarte, &c, sizeof(c), NULL, 0);
        if (ret != NRF_SUCCESS)
        {
            continue;
        }
        (void)nrf_serial_write(&serial0_uarte, &c, sizeof(c), NULL, 0);
        (void)nrf_serial_flush(&serial0_uarte, 0);

        //ret = nrf_serial_read(&serial1_uarte, &c, sizeof(c), NULL, 1000);
       // if (ret != NRF_SUCCESS)
        //{
        //    continue;
        //}
        //(void)nrf_serial_write(&serial1_uarte, &c, sizeof(c), NULL, 0);
        //(void)nrf_serial_flush(&serial1_uarte, 0);
    }
}

The result from a terminal with the a key pressed, looks:

Hello nrf_serial!
aaa�aa�aaaaaaaaaaaaaaaaaaaaaaaaaaaa�aaa��aa�aaaaaaaa�a�a�aaaaaaaaaaaaa��aaaaaaaaaaa�aaaaaaaaaaaaaaaa�aaa�a�aaaaaaaaaaaa�a��aaa�a�aaaaaaaaaaa�aaa�a��aaaaaaaa�aaaaaaaaaaaaaaaaaaaaaaaaa�aaaaaa�aa�aaaaaa�aaaaaaaaaaaaaaaaa�aaaaaaaaaaaaaaaaaa�aaaaaaaa�aaaaaaaaaaaaaaaaaaaaa�aaa�a��aaa�aaaaaaaa�aaaaaaaaaaaaaaaaa�a�aaaaaa��aaaa

I am using the DK pca_10065 board, this is running on the Release configuration, connected through the USB port to a Mac.

I am using this example as a basis for a software that should transmit data reliably between a PC and a BLE sensor on the other side, but just between the board and the PC the communication seems to be very flaky.

Will appreciate any help!

Thanks,

Juan

[Håkon Alseth]

Hi,

 

This might be inherited from the 64 MHz RC oscillator, which has a high tolerance.

Could you try starting the external HFCLK? can be done in this function: nrf_drv_clock_hfclk_request();

 

Kind regards,

Håkon

[jfarjona]

Thanks Hakon.

I tried your suggestion, both by leaving the call to:

nrf_drv_clock_lfclk_request(NULL);

and without it.  Same result.

On general guidance, which example would you recommend using as a basis for UART communications between the NRF52840 and an external board? which example/library is the most reliable?

In the last few days, I have tried so far: libuarte, serial_uartes, serial, ble_central_uart.  I see similar issues on all of them when I run loopback tests.  In the specs, it says that UART and UARTE should support full-duplex communication, but I am not seeing that with any the examples above.  It fails even at 9600 bps.

Could it be a bug on SDK 16? 

Help please, we need to get this working.

Thanks many,

Juan

[Håkon Alseth]

Hi,

 

jfarjona said:

nrf_drv_clock_lfclk_request(NULL);

Can you try calling nrf_drv_clock_hfclk_request(); and see if the issues still occurs?

 

Kind regards,

Håkon

[jfarjona]

Yes, I did.  Same result.

@snip...

int main(void) {
  ret_code_t ret;

  ret = NRF_LOG_INIT(NULL);
  NRF_LOG_DEFAULT_BACKENDS_INIT();

  
  ret = nrf_drv_clock_init();
  APP_ERROR_CHECK(ret);
  ret = nrf_drv_power_init(NULL);
  APP_ERROR_CHECK(ret);
  nrf_drv_clock_hfclk_request(NULL);
  nrf_drv_clock_lfclk_request(NULL);
  ret = app_timer_init();
  APP_ERROR_CHECK(ret);

  // Initialize LEDs and buttons.
  bsp_board_init(BSP_INIT_LEDS | BSP_INIT_BUTTONS);

  ret = nrf_serial_init(&serial0_uarte, &m_uarte0_drv_config, &serial0_config);
  APP_ERROR_CHECK(ret);

  //ret = nrf_serial_init(&serial1_uarte, &m_uarte1_drv_config, &serial1_config);
  //APP_ERROR_CHECK(ret);

  static char tx_message[] = "Hello nrf_serial!\n\r";

  ret = nrf_serial_write(&serial0_uarte,
      tx_message,
      strlen(tx_message),
      NULL,
      NRF_SERIAL_MAX_TIMEOUT);
  (void) nrf_serial_flush(&serial0_uarte, 0);
  void* buf = malloc(300);
  if ( buf == NULL ) {
    NRF_LOG_ERROR("Not enough memory!");
    ASSERT(false);
  }
  memset(buf, 0, 250);
  size_t tread = 0;
  uint32_t totB = 0;
  while (true) {
    size_t rd = 0;
    ret = nrf_serial_read(&serial0_uarte, buf, 250, &rd, 0);
    if (ret != NRF_SUCCESS && rd == 0) {
      continue;
    }
    (void) nrf_serial_write(&serial0_uarte, buf, rd, NULL, 0);
    totB = totB + rd;
    tread = tread + rd;
    if (tread > 100) {
      (void) nrf_serial_flush(&serial0_uarte, 0);
      tread = 0;
      NRF_LOG_INFO("Flushed after %d bytes", totB);
    }
   

    //ret = nrf_serial_read(&serial1_uarte, &c, sizeof(c), NULL, 1000);
    // if (ret != NRF_SUCCESS)
    //{
    //    continue;
    //}
    //(void)nrf_serial_write(&serial1_uarte, &c, sizeof(c), NULL, 0);
    //(void)nrf_serial_flush(&serial1_uarte, 0);
  }
}

[Håkon Alseth]

Hi,

 

Thanks, I have recreated the issue with your sample.

Unfortunately, I haven't been able to find a workaround on this matter, so my suggestion is to use libuarte if you require timed uart reception.

I have reported the issue internally to the SDK team so that they are aware of this issue.

 

Kind regards,

Håkon