So, let me try to explain this the best I can..

I am running a C++ program where a microcontroller accepts joystick values
and converts them to hexadecimal in order to communicate with motor drivers
installed on my robot. The string that the joystick outputs is "x-axis val
(1-3 digits), y-axis val (1-3 digits), z-axis val (1-3 digits), deadman
switch (1 digit; 0 or 1)". When I run the node and am not controlling the
joystick at all, all three axes should read 127 (neutral; values are between
0 and 255 from the joystick), but they don't. They are completely random.

I am able to observe changes in the string's values when I use the joystick,
which is good, it means the joystick is connected properly. However, I can't
for the life of me figure out why I am receiving random values
simultaneously.. we're talking a value difference of 100 at times. Has
anybody had experience with joystick and motor controller programming who
can help me out? I would sincerely appreciate it.

Here is my code:

____________________________________________________________________________________________________
 #include "ros/ros.h"
 #include "std_msgs/String.h"

 #include <sstream>
 #include <cmath>
 #include <iostream>

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

 #define PI 3.14159265358979323846264338327950288419716

 const double CIRC=0.7853981633974483, R=0.55, RATIO=127;		// initialize
constants

 int main(int argc, char **argv)
 {
	//declare all variables
	int ms1, ms2, ms3, ms4, omnibotPoseInt[4];				
	int i=0, j=0, k=0, wr, rd, x=0, y=0, z=0, fd0, fd1, fd2, numSent=0;
 	char parseChar[1], stringIn[50], mc_char, *temp;


	//set settings for HCS12 microcontroller

 	system("stty -F /dev/ttyUSB0 115200 cs8 -cstopb -parity -icanon hupcl
-crtscts min 1 time 1");	


 	//attempt to open serial port connected to the microprocessor

 	fd0 = open("/dev/ttyUSB0",O_RDWR | O_NOCTTY | O_NDELAY);	


 	//check for errors opening port	

 	if (fd0 == -1 )

 	{

		printf("open_port: Unable to open /dev/HCS12\n");

 	}

 
 	else //if no error

 	{

 		fcntl(fd0,F_SETFL,0);

		printf("Test Port HCS12 has been successfully opened and %d is the file
description\n",fd0);	

 	}

	//settings for motor driver m1 & m2
	system("stty -F /dev/ttyUSB1 9600 cs8 -cstopb -parity -icanon hupcl
-crtscts min 1 time 1");	

	//open serial port connected to motor driver for motors 1 and 2
	fd1 = open("/dev/ttyUSB1",O_RDWR | O_NOCTTY | O_NDELAY);		
	
	if (fd1 == -1 )

	{

		perror("open_port: Unable to open /dev/Driver12\n");

	}		

	else // if no error

 	{

 		fcntl(fd1,F_SETFL,0);

		printf("Test Port Driver12 has been successfully opened and %d is the file
description\n",fd1);

 	}
	
	//settings for motor driver m3 & m4
	system("stty -F /dev/ttyUSB2 9600 cs8 -cstopb -parity -icanon hupcl
-crtscts min 1 time 1");

	//open serial port connected to motor driver for motors 3 and 4
	fd2 = open("/dev/ttyUSB2",O_RDWR | O_NOCTTY | O_NDELAY);		

	if (fd2 == -1 )

	{

		perror("open_port: Unable to open /dev/Driver34\n");

	}

	else // if no error

 	{

 		fcntl(fd2,F_SETFL,0);

		printf("Test Port Driver34 has been successfully opened and %d is the file
description\n",fd2);

 	}

	// initalize node
	ros::init(argc, argv, "joyTalker");

	ros::NodeHandle joyTalker;

	// Publish to topic joyChatter
	ros::Publisher pub = joyTalker.advertise<std_msgs::String>("joyChatter",
1000);

	ros::Rate r(10);

	while (joyTalker.ok())
	{
		parseChar[0]=0;	  

		for(j=0; j<50; j++)
		{
			stringIn[j]=0;					//initialize the string
		}

		i=0;

		while(parseChar[0] != 10)
		{
			rd=read(fd0,parseChar,1);
			//printf("%s\n",parseChar);
			if ((parseChar[0] > 43 && parseChar[0] < 58) || (parseChar[0]==32))
			{
				stringIn[i]=parseChar[0];
				i++;
			}
		}
		
		// Parse the msg from the node
		temp = strtok(stringIn,",");

		k=0;

		while(temp != NULL)
		{
			omnibotPoseInt[k] = atoi(temp);
			temp = strtok(NULL,",");
			k++;
		}

		//conversion to valid motor speeds
		x = omnibotPoseInt[0]-RATIO;
		y = omnibotPoseInt[1]-RATIO;
		z = omnibotPoseInt[2]-RATIO;  	

		printf("omnibotPoseInt[0]: %d, omnibotPoseInt[1]: %d, omnibotPoseInt[2]:
%d\n", omnibotPoseInt[0], omnibotPoseInt[1], omnibotPoseInt[2]);
	
		//kinematics of the omnimaxbot according to mecanum wheels
		ms1 = ((x/sqrt(2))+y+(R*tan((z/RATIO)*(2*PI))))/CIRC;
		ms2 = (-(x/sqrt(2))+y+(R*tan((z/RATIO)*(2*PI))))/CIRC;
		ms3 = ((x/sqrt(2))+y-(R*tan((z/RATIO)*(2*PI))))/CIRC;
		ms4 = (-(x/sqrt(2))+y-(R*tan((z/RATIO)*(2*PI))))/CIRC;

		//motor controller language, specified by an exclamation mark, a character
(a or A is channel 1, b or B is channel 2), and then the speed

		if(ms1<0)				//Motor Controller 1, Channel 1, Motor 1
		{
			ms1=-ms1;
			mc_char = 'a';			//move backwards
		}
		else
		{
			mc_char = 'A';			//move forwards 
		}

		//write/send data to the specified port
		numSent = sprintf(stringIn, "!%c%2X", mc_char, ms1);	
		wr = write(fd1,stringIn,numSent);

		if(ms2<0)				//Motor Controller 1, Channel 2, Motor 2
		{
			ms2=-ms2;
			mc_char = 'b';			//move backwards			
		}
		else
		{
			mc_char = 'B';			//move forwards
		}

		numSent = sprintf(stringIn, "!%c%2X", mc_char, ms2);
		wr = write(fd1,stringIn,numSent);

		if(ms3<0)				//Motor Controller 2, Channel 1, Motor 3
		{
			ms3=-ms3;
			mc_char = 'a';					
		}
		else
		{
			mc_char = 'A';		
		}

		numSent = sprintf(stringIn, "!%c%2X", mc_char, ms3);
		wr = write(fd2,stringIn,numSent);

		if(ms4<0)				//Motor Controller 2, Channel 2, Motor 4
		{
			ms4=-ms4;
			mc_char = 'b';			
		}
		else
		{
			mc_char = 'B';
		}			

		numSent = sprintf(stringIn, "!%c%2X", mc_char, ms4);
		wr = write(fd2,stringIn,numSent);			       

		printf("got this string %s\n",stringIn);

		// convert message to string for ROS node communication
		std_msgs::String msg;
		std::stringstream ss;
		ss << stringIn;
		ROS_INFO("%s", ss.str().c_str());
		msg.data = ss.str();
		// publish data under topic joyChatter
		pub.publish(msg);

		ros::spinOnce();
	}

 return 0;
 }
____________________________________________________________________________________________________
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