Saturday, July 7, 2012

Arduino: Sending integers over RF with VirtualWire

When I tried to send the output from a sensor over RF with VirtualWire I quickly learned that it wasn't as simple as one two three.

But eventually I got it working with a little help from the good folks at the Arduino forum

VirtualWire is a library that makes it really easy to transmit using RF modules. I've successfully used two different kinds of 434 Mhz modules with it but it has support for other types aswell. 

The code and comments below are pretty much self explanatory:

Transmitter (download source code)

Sensor Transmitter
By Markus Ulfberg 2012-07-06

Takes a sensor reading 0-1023
converts it to a char array and sends 
to RF receiver unit via VirtualWire  


#include <VirtualWire.h>

// LED's
const int ledPin = 13;

// Sensors 
const int Sensor1Pin = A2;
// const int Sensor2Pin = 3; 

int Sensor1Data;
//int Sensor2Data;
char Sensor1CharMsg[4]; 

void setup() {

 // PinModes 
 // LED 
 // Sensor(s)
 // for debugging
 // VirtualWire setup
 vw_setup(2000);     // Bits per sec


void loop() {
  // Read and store Sensor 1 data
  Sensor1Data = analogRead(Sensor1Pin);
  // Convert integer data to Char array directly 
  // DEBUG
  Serial.print("Sensor1 Integer: ");
  Serial.print(" Sensor1 CharMsg: ");
  Serial.println(" ");

 digitalWrite(13, true); // Turn on a light to show transmitting
 vw_send((uint8_t *)Sensor1CharMsg, strlen(Sensor1CharMsg));
 vw_wait_tx(); // Wait until the whole message is gone
 digitalWrite(13, false); // Turn off a light after transmission
} // END void loop...

Receiver (download source code)

Sensor Receiver 
By Markus Ulfberg 2012-07-06

Gets a sensor reading 0-1023 in a char array
from RF Transmitter unit via VirtualWire 
converts char array back to integer


#include <VirtualWire.h>

// LED's
int ledPin = 13;

// Sensors 
int Sensor1Data;

// RF Transmission container
char Sensor1CharMsg[4]; 

void setup() {
  // sets the digital pin as output
  pinMode(ledPin, OUTPUT);      
    // VirtualWire 
    // Initialise the IO and ISR
    // Required for DR3100
    // Bits per sec
    // Start the receiver PLL running

} // END void setup

void loop(){
    uint8_t buf[VW_MAX_MESSAGE_LEN];
    uint8_t buflen = VW_MAX_MESSAGE_LEN;
    // Non-blocking
    if (vw_get_message(buf, &buflen)) 
    int i;
        // Turn on a light to show received good message 
        digitalWrite(13, true); 
        // Message with a good checksum received, dump it. 
        for (i = 0; i < buflen; i++)
          // Fill Sensor1CharMsg Char array with corresponding 
          // chars from buffer.   
          Sensor1CharMsg[i] = char(buf[i]);
        // Null terminate the char array
        // This needs to be done otherwise problems will occur
        // when the incoming messages has less digits than the
        // one before. 
        Sensor1CharMsg[buflen] = '\0';
        // Convert Sensor1CharMsg Char array to integer
        Sensor1Data = atoi(Sensor1CharMsg);
        // DEBUG 
        Serial.print("Sensor 1: ");
        // END DEBUG
        // Turn off light to and await next message 
        digitalWrite(13, false);

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