#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>		/* For the termio struct */
#include <stdio.h>
#include <unistd.h>		/* For write() */
#include <stdlib.h>		/* For exit(), malloc() and free() */
#include <math.h>
#include <string.h>
#include <unistd.h>

/* baudrate settings are defined in <asm/termbits.h>, which is
   included by <termios.h> */
#define BAUDRATE B9600
/* change this definition for the correct port */
#define SERIAL_PORT "/dev/ttyUSB0"
#define _POSIX_SOURCE 1 /* POSIX compliant source */

#define FALSE 0
#define TRUE 1

/* Number of samples in the generated waveform, between 8 and 16000 */
#define N_SAMPLES 8

volatile int STOP=FALSE; 


/* Function prototypes */
void port_setup(int fd, struct termios *ios);
void init_hp(int fd);
void write_port(int fd, char *buf);
void write_char(int fd, char *buf);
void restore_settings(int fd, struct termios *ios);




/****************************************************************************/
int main(void)
{
    struct termios *oldtio;	/* Save current serial port settings in here */
    oldtio = (termios*)malloc( sizeof(struct termios) );

    int fd;			/* File descriptor for the serial port */

    /* 
       Open modem device for reading and writing and not as controlling tty
       because we don't want to get killed if linenoise sends CTRL-C.
    */
    printf("Opening serial port...\n");
    fd = open(SERIAL_PORT, O_RDWR | O_NOCTTY); 
    if (fd <0) {perror(SERIAL_PORT); exit(-1); }
    
    printf("Setting up serial port...\n");
    port_setup(fd, oldtio);

    init_hp(fd);
    
    //make_waveform(fd);

    restore_settings(fd, oldtio);
    free(oldtio);
	
    return 0;

}


/****************************************************************************/
void port_setup(int fd, struct termios *oldtio)
{
    /*
      Most of this function was copied directly from the Linux Serial 
      Programming HOWTO. 
    */

    struct termios newtio;

    tcgetattr(fd, oldtio); /* save current serial port settings */
    bzero(&newtio, sizeof(newtio)); /* clear struct for new port settings */
        
    /* 
       BAUDRATE: Set bps rate. You could also use cfsetispeed and cfsetospeed.
       CRTSCTS : output hardware flow control (only used if the cable has
       all necessary lines. See sect. 7 of Serial-HOWTO)
       CS8     : 8n (8bit,no parity), needed for sending arb. waveforms, 
                  see page 195 in the HP user manual.
       CSTOPB  : 2 stopbits (remove for 1)
       CLOCAL  : local connection, no modem contol
       CREAD   : enable receiving characters
    */
    //newtio.c_cflag = BAUDRATE | CS8 | CSTOPB | CLOCAL | CREAD;
    newtio.c_cflag = BAUDRATE | CS8 | CLOCAL | CREAD;
     
    /*
      IGNPAR  : ignore bytes with parity errors
      ICRNL   : map CR to NL (otherwise a CR input on the other computer
      will not terminate input)
      otherwise make device raw (no other input processing)
    */
    newtio.c_iflag = IGNPAR;
         
    /*
      Raw output.
    */
    newtio.c_oflag = 0;

    /*
      ICANON  : enable canonical input
      disable all echo functionality, and don't send signals to calling program
    */
    newtio.c_lflag = ICANON;

    /* 
       now clean the modem line and activate the settings for the port
    */
    tcflush(fd, TCIFLUSH);
    tcsetattr(fd, TCSANOW, &newtio);
        
    /*
      terminal settings done, now we can handle input
    */
}


/***************************************************************************/
void init_hp(int fd)
{
    /* Initialisation of the function generator */
    
    write_port(fd, "SYSTEM:REMOTE");
    write_port(fd, "*RST");
    write_port(fd, "*CLS");
    write_port(fd, "APPL:SIN 401");
    
    //usleep(1000);
    //write_char(fd, "S");
    //write_port(fd, "FORM:BORD SWAP"); /* Swap data bytes, send LSB first */
    //write_port(fd, "OUTP:LOAD 50"); /* Output termination is 50 Ohm */
}


/***************************************************************************/
void write_port(int fd, char *buffer)
{
    /* Write a command to the HP. All commands are terminated by a \n. */

    int end;
    end = strlen(buffer);
    char buf[end];

    strcpy(buf, buffer);
    end = strlen(buf);
    buf[end] = '\n';		/* Add a newline to the command */
    buf[end + 1] = 0;

    write(fd, buf, strlen(buf));

}

void write_char(int fd, char *buffer)
{
    
    write(fd, buffer, 1);

}


/***************************************************************************/
void restore_settings(int fd, struct termios *ios)
{
    /* restore the old port settings */
    printf("Restoring tty settings... \n");
    tcsetattr(fd, TCSANOW, ios);
}