/* Last modified on Sun Feb 25 2007, Hal Murray */

/*
 *  This is a hack/demo program to test/exercise the Prologix GPIB-USB
 *  board on a Linux system.  It's what I was looking for when I
 *  was trying to get mine going.

 *  This is setup to talk to /dev/ttyUSB1
 *  Edit to match your system.

 *  Prologix info at: http://prologix.googlepages.com/
 *  More GPIB info at http://www.ko4bb.com/Test_Equipment/GPIB.html

 *  Prologix says their board goes into blink mode if you get
 *  the baud rate wrong.  It also blinks if you send another
 *  command while it's still processing the previous one.
 *  That can happen if you don't have the flow control setup right.

 *  Linux kernels somewhere between 2.4.16 and 2.6.19 made a major
 *  cleanup to the USB drivers.  The flow control code was split
 *  out into the SERIAL_GENERIC module.  It wasn't getting loaded
 *  on my system.  I don't know why.  I included it in the kernel
 *  and build a new one.  Before I did that, I had things working
 *  with a 50 ms pause after sending each command.

 *  The cruft sprinkled throughout this code is leftover from my debugging.
 *  It's a good place to add printout if you are chasing similar problems.

 *  I compile with:
 *  cc -O2 -Wall -Wstrict-prototypes -Wmissing-prototypes -g -o probe probe.c


 *  I have a HP 5334B on device address 3.
 *  This hack is setup to read the frequency.
 *  If you have something similar it will printout something like this.
 *  If you are trying to get off the ground, I suggest disconnecting
 *  all devices until you see the version string from the Prologix card.
 *  If you have something connected, don't be surprsied
 *  if you get some extra printout.  Your device may be running
 *  in continious mode (Single Cycle off) sending an answer occasionally.
 *  If the answer arrives "too soon" the printout may get garbled.

    Flushing input..........
    Here we go...
    << ++ver
    >> Prologix GPIB-USB Controller version 3.12d
    << ++addr 3
    << ID
    >> HP5334B
    << IN
    >>??
    << GV0
    << GS1
    << FN1
    Got: "F    +9.9999993E+06"

 */

char *port = "/dev/ttyUSB1";

// 1 to use hardware flow control (what Prologix expects)
// 0 to try without
#define FLOW 1

#include <errno.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h> 
#include <termios.h>
#include <unistd.h>
#include <sys/ioctl.h>
#include <sys/types.h>


// I have an HP 5334B at this address
#define ADDR 3

/* prototypes */
void SetupGPIB(void);
void SendCommand(char* cmd);
void SendEOL(void);
char* GetAnswer(int seconds);
void PrintResponse(void);

int fd = -1;

void SetupGPIB() {
  int err, i;
  struct termios mode;
  /* need NONBLOCK to avoid hanging if LOCAL flag isn't set */
  /* At least on real TTYs. */
  fd = open(port, O_RDWR | O_NONBLOCK);
  if (fd < 0) {
    printf("# Can't open %s: %s\n", port, strerror(errno));
    sleep(10);
    exit(1);
  }
  /* Setup all the mode bits.  Check with: stty -a -F /dev/ttyUSB1 */
  err = tcgetattr(fd, &mode);
  if (err < 0) {
    printf("# tcsetattr failed: %s\n", strerror(errno));
    sleep(10);
    exit(1);
  }
  if (0) printf("Initial modes: if: %x, of: %x, cf: %x, lf: %x\n",
    mode.c_iflag, mode.c_oflag, mode.c_cflag, mode.c_lflag);
// printf("Before tcsetattr\n");
// sleep(10);
  mode.c_cflag |= CS8;           // 8 data bits
  mode.c_cflag &= ~PARENB;       // No parity
  mode.c_cflag &= ~CSTOPB;       // 1 stop bit
  mode.c_cflag |= CLOCAL;
  if (FLOW)
    mode.c_cflag |= CRTSCTS;     // Hardware flow control on
  else
    mode.c_cflag &= ~CRTSCTS;    // Hardware flow control off
  cfsetispeed(&mode, B115200);
  cfsetospeed(&mode, B115200);
  mode.c_lflag &= ~ECHO;         // No local echo
  err = tcsetattr(fd, TCSANOW, &mode);
  if (err < 0) {
    printf("# tcsetattr failed: %s\n", strerror(errno));
    sleep(10);
    exit(1);
  }
  if (0) printf("Initial modes: if: %x, of: %x, cf: %x, lf: %x\n",
    mode.c_iflag, mode.c_oflag, mode.c_cflag, mode.c_lflag);
// printf("After tcsetattr\n");
// sleep(10);
  printf("Flushing input");
  for (i=0; i<10; i++) {
    err = tcflush(fd, TCIOFLUSH);
    if (err < 0) {
      printf("# tcflush failed: %s\n", strerror(errno));
      sleep(10);
      exit(1);
    }
    printf(".");
    usleep(50000);
  }
  printf("\n");
// printf("After tcflush\n");
// sleep(1);
// printf("## Opened...\n");
// sleep(10);
  if (!FLOW) {
    int bits = TIOCM_DTR | TIOCM_RTS;
    err = ioctl(fd, TIOCMBIS, &bits); /* Turn on DTR and RTS */
    if (err < 0) {
      printf("# Can't set DTR: %s\n", strerror(errno));
      sleep(10);
      exit(1);
    }
    printf("## No FLOW, Turned on DTR and RTS.\n");
  }
}

static int lines = 0;
void SendEOL()
{
  int err;
  if (0) printf("## Sending EOL (%d)\n", lines++);
  err = write(fd, "\r\n", 2);
  if (err != 2) {
    printf("# Can't send EOL (%d): %s\n", err, strerror(errno));
    sleep(10);
    exit(1);
  } 
  if (!FLOW) usleep(50000);  // Hack to avoid blink mode without flow control
}

void SendCommand(char* cmd)
{
  size_t length = strlen(cmd);
  int err;
  if (0) printf("## Sending command: %s (%d)\n", cmd, length);
  if (1) printf("<< %s\n", cmd);
  err = write(fd, cmd, length);
  if (err != length) {
    printf("# Can't send command: %s\n", strerror(errno));
    sleep(10);
    exit(1);
  }
  SendEOL();
}

#define LINESIZE 1000
void PrintResponse() {
  int err, i, len;
  char line[LINESIZE+1];
  for (i = 0; i < LINESIZE; i++) {
    err = read(fd, &line[i], 1);
    if (err == -1) {
      // try again
      if (i==0) usleep(100000);
      usleep(100000);
      err = read(fd, &line[i], 1);
    }
    if (err == -1) { line[i] = 0; break; }
    if (0) printf("i=%d, c=%c\n", i, line[i]);
    if (0) fflush(stdout);
    // Prologix normally uses \r\n.  Dump \r.
    if (line[i] == '\r') i--;
  }
  if (i == 0) {
    // No response
    printf(">>??\n");
    return;
  }
  // Chop off trailing \ns.  There are normally 2 of them.
  for ( ; i>0; i--) {
    if (line[i-1] != '\n') break;
    line[i-1] = 0;
  }
  len = i;
  for (i=0; i<len-1; i++) {
    // Multi-line answer.  This doesn't normally happen.
    if (line[i] == '\n') printf("> NL at %d\n", i);
  }
  printf(">> %s\n", line);
}

char answer[LINESIZE+1];
char* GetAnswer(int seconds) {
  int err, i, len;
  char *line = answer;
  for (i = 0; i < LINESIZE; i++) {
    err = read(fd, &line[i], 1);
    if (err == -1) {
      // Not ready yet
      if ((i==0) && (seconds > 0)) {
        // printf(".");
        sleep(1);
        i--;
        seconds--;
        continue;
      }
      usleep(25000);
      err = read(fd, &line[i], 1);
    }
    if (err == -1) { line[i] = 0; break; }
    if (0) printf("i=%d, c=%c\n", i, line[i]);
    if (0) fflush(stdout);
    // Prologix normally uses \r\n.  Dump \r.
    if (line[i] == '\r') i--;
  }
  if (i == 0) {
    // No response
    // printf(">>??\n");
    return(NULL);
  }
  // Chop off trailing \ns in answer.  There are normally 2 of them.
  for ( ; i>0; i--) {
    if (line[i-1] != '\n') break;
    line[i-1] = 0;
  }
  len = i;
  // printf(">len=%d\n", len);
  for (i=0; i<len-1; i++) {
    if (line[i] == '\n') printf("> NL at %d\n", i);
  }
  // printf(">> %s", line);
  return(answer);
}


int main(int argc, char *argv[])
{

  char *ans;
  char cmd[100];

  if (argc > 1) {
    printf("Don't know what to do with args.\n");
    sleep(10);
    exit(1);
  }

  SetupGPIB();

  printf("Here we go...\n");
  SendEOL();

  SendCommand("++ver");
  PrintResponse();

  // I have an HP 5334B at device address 3
  sprintf(cmd, "++addr %d", ADDR);
  SendCommand(cmd);

  SendCommand("ID");    // What device?  (if any)
  PrintResponse();

  SendCommand("IN");    // Initialize
  // PrintResponse();   no response

  SendCommand("GV0");   // 100 cycle average off
  SendCommand("GS1");   // Single cycle on
  SendCommand("FN1");   // Measure Frequency on Chan A
  ans = GetAnswer(2);
  if (ans) printf("Got: \"%s\"\n", ans);
  else printf("No answer.\n");
  exit(0);

}