Problem sending chars

[Pinout_1]

Hi team,

I have to create a program which sends messages from one dongle to another. Now I have ported radio transmit and receive + USB CDC ACM programs for two 52840 dongles. Also each of them can be seen as USB serial devices and can output messages on the terminal. Now, I can transmit only integers... How to transmit chars? When I try to use sprintf function I get hieroglyphs on the terminal. Also I tried to set packet variable with some chars on the tx side and then I got ASCII values in the other side... Thanks for the answers.

Rx dongle main():

ret_code_t ret;
  static const app_usbd_config_t usbd_config = {
      .ev_state_proc = usbd_user_ev_handler
  };

  bsp_board_init(BSP_INIT_LEDS);
  
  nrf_drv_clock_init(); 
  nrf_drv_clock_hfclk_request(NULL); // for HF 32MHz external X-tal
  while(!nrf_drv_clock_hfclk_is_running()) ; // Just waiting
  nrf_drv_clock_lfclk_request(NULL); // for LF 32.768kHz external X-tal
  while(!nrf_drv_clock_lfclk_is_running()) ; 
  /// end clock set

 /// end clock set
  app_usbd_serial_num_generate();
  ret = app_usbd_init(&usbd_config);
  APP_ERROR_CHECK(ret);

  app_usbd_class_inst_t const * class_cdc_acm = app_usbd_cdc_acm_class_inst_get(&m_app_cdc_acm);
  ret = app_usbd_class_append(class_cdc_acm);
  APP_ERROR_CHECK(ret);

  if (USBD_POWER_DETECTION) {
      ret = app_usbd_power_events_enable();
      APP_ERROR_CHECK(ret);
  }
  else {
      app_usbd_enable();
      app_usbd_start();
  }


 radio_configure();
 NRF_RADIO->PACKETPTR = (uint32_t)&packet;
 
while(true)
  {

uint32_t             received = read_packet();
char result[3]; 

sprintf(result,"%ul",received);

size_t size = sprintf(m_tx_buffer,result, frame_counter);
ret = app_usbd_cdc_acm_write(&m_app_cdc_acm, m_tx_buffer, size);

if (ret == NRF_SUCCESS)
  {
   ++frame_counter;
  }

  nrf_delay_ms(10);
  }
}

Tx dongle main():

ret_code_t ret;
  static const app_usbd_config_t usbd_config = {
      .ev_state_proc = usbd_user_ev_handler
  };

  bsp_board_init(BSP_INIT_LEDS);

  nrf_drv_clock_init(); 
  nrf_drv_clock_hfclk_request(NULL); // for HF 32MHz external X-tal
  while(!nrf_drv_clock_hfclk_is_running()) ; // Just waiting
  nrf_drv_clock_lfclk_request(NULL); // for LF 32.768kHz external X-tal
  while(!nrf_drv_clock_lfclk_is_running()) ; // Just waiting

  app_usbd_serial_num_generate();
  ret = app_usbd_init(&usbd_config);
  APP_ERROR_CHECK(ret);

  app_usbd_class_inst_t const * class_cdc_acm = app_usbd_cdc_acm_class_inst_get(&m_app_cdc_acm);
  ret = app_usbd_class_append(class_cdc_acm);
  APP_ERROR_CHECK(ret);

  if (USBD_POWER_DETECTION) {
      ret = app_usbd_power_events_enable();
      APP_ERROR_CHECK(ret);
  }
  else {
      app_usbd_enable();
      app_usbd_start();
  }

  radio_configure();
  NRF_RADIO->PACKETPTR = (uint32_t)&packet;   // Set payload pointer

  while(true)
  {
  app_usbd_event_queue_process();

if (packet != 0) {

  send_packet();
  m_send_flag;
  static int  frame_counter;
  
  nrf_delay_ms(10); 
  
    }
  }
}

[ryerye120]

In the end, you're just sending and receiving bits. So what are you sending and how are you casting on the RX side? It looks like you're printing them as 'unsigned longs'. Try sending a string and printing it with %s. 

On the Tx side you can make a test string like this:

#define TEST_STRING "comes_from_tx"
static uint8_t       m_tx_buf[] = TEST_STRING;

and then on the rx side you can debug with NRF log:

NRF_LOG_INFO(" Transfer completed. Received: %s",(uint32_t)m_rx_buf);

[Pinout_1]

Thanks ryerye120, according to your suggestion, I made a few changes in my code, now I'm able to see strings. But now I have other problem - I can see only one string. For example when I declare a string in the Tx side, I get H word in the Rx side. Maybe it is CDC ACM problem?

[ryerye120]

That may have something to do with how the CDC ACM example processes received chars from the keyboard. So depending on when you print you may only get one character at a time. How are you triggering the transmissions? Do you have an example that allows for typing in one terminal and transmitting that to another?