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Mechanics and Construction => Mechanics and Construction => Topic started by: ROVER on January 16, 2013, 05:22:20 PM

Title: need help with xbee
Post by: ROVER on January 16, 2013, 05:22:20 PM

I would like to seek help how do I get by using two xbee and its shield and arduino uno

I am using this code to run the dc motor of my remote truck to go forward and backward, I was able to make it move using this code, now I am trying to work it wirelessly using xbee, but I am kinda loss, I thought I could just copy this code again to the other arduino and hooked up the xbee and the shield, any help would be appreciated

Code: [Select]

const int in1 = 2;    // direction pin 1
const int in2 = 4;    // direction pin 2
const int ena = 3;    // PWM pin to change speed
 
int pot;              // integer for potentiometer
int fspeed;           // forward speed
int bspeed;           // backward speed
 
void setup() {
  pinMode(in1, OUTPUT);
  pinMode(in2, OUTPUT);
  pinMode(ena, OUTPUT);
}
 
void loop() {
  pot = analogRead(A0);
 
  if (pot >= 480 && pot <= 540)
  {
    stop();
  }
  if (pot < 500)
  {
    fspeed = map(pot, 479, 0, 70, 250);
    forward(fspeed);
  }
  if (pot > 520)
  {
    bspeed = map(pot, 541, 1023, 70, 250);
    backward(bspeed);
  }
}
 
void stop()
{
  analogWrite(ena, 0);
}
 
void forward(int fspeed)
{
  digitalWrite(in1, HIGH);
  digitalWrite(in2, LOW);
  analogWrite(ena, fspeed);
}
 
void backward(int bspeed)
{
  digitalWrite(in1, LOW);
  digitalWrite(in2, HIGH);
  analogWrite(ena, bspeed);
}

(http://imageshack.us/a/img41/5827/01162013135.jpg) (http://imageshack.us/photo/my-images/41/01162013135.jpg/)

(http://imageshack.us/a/img688/7294/01162013134.jpg) (http://imageshack.us/photo/my-images/688/01162013134.jpg/)

(http://imageshack.us/a/img24/3216/01162013136.jpg) (http://imageshack.us/photo/my-images/24/01162013136.jpg/)

Title: Re: need help with xbee
Post by: jwatte on January 18, 2013, 11:13:53 AM

The XBees are serial devices. You need to hook the XBee on each end to a serial port.
I would recommend using SoftwareSerial on the sending Arduino (on some pins other than 0 and 1,) so you don't get interference with programming the board.
You can use the hardware serial port (pins 0 and 1) on the receiving Arduino.

Then, build a simple protocol, and send commands over the serial wire. A simple protocol might be:

0xEE <command byte> <parameter byte>>

So, a command might be "Set forward speed." Call this 0x01. The parameter is the speed value (0 - 255.) Your sending Arduino would then do something like this:

Code: [Select]

enum {
  CMD_FORWARD = 0x1,
  CMD_TURN = 0x2
};
SoftwareSerial ss(...);

void sendForward(unsigned char val) {
  unsigned char data[3] = { 0xEE, CMD_FORWARD, val };
  ss.write(3, data);
}

On the receiving end, you have to receive and decode commands. You should be getting one byte at a time -- you can't assume that a full command will be coming in in a single read request. The algorithm looks something like:

Code: [Select]

unsigned char buffer[3];
unsigned char bufptr = 0;

void handle_command() {
  switch (buffer[1]) {
    case CMD_FORWARD:
      ... value is in buffer[2];
      break;
    ....
  }
}

void read_one() {
  if (myserialport has data) {
    buffer[bufptr] = read one byte;
    if ((bufptr == 0 && buffer[0] == 0xEE) || (bufptr > 0)) {
      ++bufptr; // in a packet
    }
    if (bufptr == 3) { // packet finished
      handle_command();
      bufptr = 0;
    }
  }
}