/*
 * hoitek.cpp
 * by Bernd Herd (C) 2009 (herdsoft.com)
 *
 * Based on:
 * tenma.c
 * by Robert Kavaler (c) 2009 (relavak.com)
 *
 * Utility program to read daata from a Houtek HID UART device.
 * This device is used in the USB cable for PeakTech 3315 DMM devices
 * and Likely Tinma 72-7730 DMM.
 *
 * Based on linux /dev/hidraw interface. This code is written as a driver with
 * some unit test code to show how to incorporate it into an application.
 *
 * To operate the unit test software:
 * 1. Plug the USB cable into your computer.
 * 2. Check which /dev/hidraw device was created. Normally it is /dev/hidraw0.
 * 3. Check for permissions. Maybe do chmod o+rw /dev/hidraw0 as root, or
 *    chgrp dialout /dev/hidraw0
 * 4. Compile the code: gcc -o hoitek hoitek.c
 * 5. Run the code using the device name as a parameter:
 *    ./hoitek /dev/hidraw0
 * 6. Turn on the DMM.
 * 7. Press the RS232 button the on the DMM for one second, it will beep.
 * 8. Have fun.
 *
 * This will display the raw data read from the device.
 * To interpret the data read you will need a DMM-Specific filter,
 * for example by calling:
 *
 * ./hoitek /dev/hidraw1 | ./peaktech3315
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; either version 2 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 *
 */



#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <string.h>
#include <math.h>

/**
 * Open the given device
 *
 * @param devicename     Filename of the /dev entry to open
 * @param bps            Bits per second, 2400 for PeakTech 3315 and Tenma 72-7730
 *
 *
 * @return File descriptor to be closed by a call to close(fd),
 *         -1 on errors.
 */
int
hoitek_open(const char *devicename, int bps)
{
  unsigned char buf[6];
  int fd = open(devicename, O_RDWR);
  if(fd >= 0)
    {
      buf[0] = 0;
      buf[1] = bps;
      buf[2] = bps>>8;
      buf[3] = bps>>16;
      buf[4] = bps>>24;
      buf[5] = 3;			// 3 = 8 bits no parity??
      if(write(fd, buf, sizeof(buf)) != sizeof(buf)) 
        {
          perror("write hoitek config header");
          close(fd);
          fd = -1;
        }
	}
  else
    {
      perror("open");
    }

  return fd;
}



int
main(int argc, const char **argv)
{
  int fd = hoitek_open( argc>1 ? argv[1] : "/dev/hidraw0", 2400 );
  if (fd != -1)
    {
      unsigned char buf[8];
      int error=0;
      do
        {
          error = read(fd, buf, sizeof(buf))!=sizeof(buf);
          if (error)
            {
              perror("read");
            }
          else
            {
              int i;
              int len=buf[0] & 7;

              for (i=0; i<len; i++)
                buf[i+1] &= 0x7f;

              error = fwrite(buf+1, 1, len, stdout) != len;
              if (error)
                {
                  perror("fwrite");
                }
              fflush(stdout);
            }
        }
      while (!error);
      close(fd);
    }
  return fd==-1 ? EXIT_FAILURE : EXIT_SUCCESS;
}