Re: FT232RL Reading DMX

[Rui Barreiros]

Hello Thomas, I did a ftdi_read_data_set_chunksize(ftdi, 513) and commented out the purge, still the data I'm receiving is not 'correct' there are 512 positions (the 1st of the 513 array is the start code which is always 0x00) which correspond to a DMX channel, and I keep getting the correct value but always on the wrong array positions, they keep changing. Also, the break interrupt seems to be slower than what it should be. Attached goes my latest test code. Best regards, On 05/30/2012 05:57 PM, Thomas Jarosch wrote: Hi Rui, On Wednesday, 30. May 2012 17:09:04 Rui Barreiros wrote: while(!exitRequested) { ftdi_poll_modem_status(ftdi, &status); if(status & 0x1000) { // BREAK_INTERRUPT f = ftdi_read_data(ftdi, buff, sizeof(buff)); if(f < 0) sleep(1); else if(f > 0) { ftdi_usb_purge_rx_buffer(ftdi); fprintf(stdout, "Read %d bytes\n", f); for(i = 0; i < sizeof(buff); i++) { fprintf(stdout, "%02X ", ((unsigned char *) buff)[i] ); } I'm not sure if the ftdi_usb_purge_rx_buffer() is a good idea: ftdi_read_data() reads data in "readbuffer_chunksize" blocks, usually 4096 bytes. If the "sizeof(buff)" (=513) is smaller than that and the chip returns more data, it will be buffered internally. Next time you call ftdi_read_data(), it might return data from the internal read buffer. The problem is that ftdi_usb_purge_rx_buffer() clears the internal read buffer, so you will experience data loss. Do you really need ftdi_usb_purge_rx_buffer()? Thomas -- Rui Barreiros rui.barrei...@audioluz.net Tlm: +351 962 356 020 Rua Alminhas das Cais, 950 4410-497 Serzedo VNG Portugal NIF: 506 107 523 Tlm: +351 968 015 215 Tlf: +351 227 625 805 Fax: +351 227 534 304 ge...@audioluz.net libftdi - see http://www.intra2net.com/en/developer/libftdi for details. To unsubscribe send a mail to libftdi+unsubscr...@developer.intra2net.com

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <signal.h>
#include <ftdi.h>

static int exitRequested = 0;

static void
sigintHandler(int signum)
{
  fprintf(stderr, "Shutdown requested\n");
  exitRequested = 1;
}

int main(int argc, char **argv)
{
  int f = 0, i = 0, tmp = 0;
  unsigned short status = 0;
  struct ftdi_context *ftdi;
  unsigned char buff[513];
  int VID = 0x0403;
  int PID = 0x6001;

  if ((ftdi = ftdi_new()) == 0) {
    fprintf(stderr, "ftdi_new failed\n");
    return EXIT_FAILURE;
  }

  fprintf(stdout, "Opening...\n");
  if(ftdi_usb_open_desc(ftdi, VID, PID, "USB Serial Converter", "MYSERIALNUMBER") < 0) {
    fprintf(stderr, " ftdi_usb_open failed\n");
    fprintf(stderr, "%s\n", ftdi_get_error_string(ftdi));
    exit -1;
  }

  fprintf(stdout, "Reset...\n");
  if(ftdi_usb_reset(ftdi) < 0) {
    fprintf(stderr, " ftdi_usb_reset failed\n");
    fprintf(stderr, "%s\n", ftdi_get_error_string(ftdi));
    exit -1;
  }

  fprintf(stdout, "Setting Line Properties...\n");
  if(ftdi_set_line_property2(ftdi, BITS_8, STOP_BIT_2, NONE, BREAK_ON) < 0) {
    fprintf(stderr, " ftdi_set_line_property failed\n");
    fprintf(stderr, "%s\n", ftdi_get_error_string(ftdi));
    exit -1;
  }
  
  fprintf(stdout, "Setting Baudrate...\n");
  if(ftdi_set_baudrate(ftdi, 250000) < 0) {
    fprintf(stderr, " ftdi_set_baudrate failed\n");
    fprintf(stderr, "%s\n", ftdi_get_error_string(ftdi));
    exit -1;
  }

  fprintf(stdout, "Setting Flow Ctrl...\n");
  if(ftdi_setflowctrl(ftdi, SIO_RESET) < 0) {
    fprintf(stderr, " ftdi_set_setflowctrl failed\n");
    fprintf(stderr, "%s\n", ftdi_get_error_string(ftdi));
    exit -1;
  }

  fprintf(stdout, "Purging Buffers...\n");
  if(ftdi_usb_purge_buffers(ftdi) < 0) {
    fprintf(stderr, " ftdi_usb_purge_buffers failed\n");
    fprintf(stderr, "%s\n", ftdi_get_error_string(ftdi));
    exit -1;
  }

  fprintf(stdout, "Setting RTS...\n");
  if(ftdi_setrts(ftdi, SIO_SET_RTS_HIGH) < 0) {
    fprintf(stderr, " ftdi_setrts failed\n");
    fprintf(stderr, "%s\n", ftdi_get_error_string(ftdi));
    exit -1;
  }

  ftdi_read_data_set_chunksize(ftdi, 513);
  ftdi_read_data_get_chunksize(ftdi, &tmp);
  fprintf(stdout, "Chunksize = %d\n", tmp);
  
  signal(SIGINT, sigintHandler);
  fprintf(stdout, "Starting Loop...\n");
  while(!exitRequested) {
    ftdi_poll_modem_status(ftdi, &status);

    if(status & 0x1000) { // BREAK_INTERRUPT

      f = ftdi_read_data(ftdi, buff, sizeof(buff));
      if(f < 0)
        sleep(1);
      else if(f > 0) {
        fprintf(stdout, "Read %d bytes\n", f);
        for(i = 0; i < sizeof(buff); i++) {
          fprintf(stdout, "%02X ", ((unsigned char *) buff)[i] );
        }
        
        fprintf(stdout, "\n");
        fflush(stdout);
      }
    } // BREAK INTERRUPT

  }

  signal(SIGINT, SIG_DFL);
  ftdi_usb_close(ftdi);
  ftdi_free(ftdi);

  return 0;
}