ide-usb/Core/Src/cdc.c

#include "main.h"
#include "cmsis_os.h"
#include "cdc.h"
#include "tusb.h"

// echo to either Serial0 or Serial1
// with Serial0 as all lower case, Serial1 as all upper case
static void echo_serial_port(uint8_t itf, uint8_t buf[], uint32_t count)
{
  uint8_t const case_diff = 'a' - 'A';

  for(uint32_t i=0; i<count; i++)
  {
    if (itf == 0)
    {
      // echo back 1st port as lower case
      if (isupper(buf[i])) buf[i] += case_diff;
    }
    else
    {
      // echo back 2nd port as upper case
      if (islower(buf[i])) buf[i] -= case_diff;
    }

    tud_cdc_n_write_char(itf, buf[i]);
  }
  tud_cdc_n_write_flush(itf);
}

//--------------------------------------------------------------------+
// USB CDC
//--------------------------------------------------------------------+
void cdctask(void)
{
  uint8_t itf;

  for (itf = 0; itf < CFG_TUD_CDC; itf++)
  {
    // connected() check for DTR bit
    // Most but not all terminal client set this when making connection
    // if ( tud_cdc_n_connected(itf) )
    {
      if ( tud_cdc_n_available(itf) )
      {
        uint8_t buf[64];

        uint32_t count = tud_cdc_n_read(itf, buf, sizeof(buf));

        // echo back to both serial ports
        echo_serial_port(0, buf, count);
        echo_serial_port(1, buf, count);
      }
    }
  }
}