Arduino RF Link

I bought two RF links from SparkFun a while back (a 315Mhz and a 434Mhz). A few nights ago, I actually hooked one of them up and successfully ran a test program between two Arduinos. Here's the code for the receiver:
#define rxPin 2
#define txPin 3

byte incomingByte = 0;

SoftwareSerial rfSerial = SoftwareSerial(rxPin, txPin);

void setup() {
pinMode(rxPin, INPUT);
pinMode(txPin, OUTPUT);
rfSerial.begin(2400);
Serial.begin(2400);
}

void loop() {
incomingByte = rfSerial.read();
Serial.println(incomingByte, DEC);
incomingByte = 0;
}
And for the transmitter:
#define rxPin 2
#define txPin 3

SoftwareSerial rfSerial = SoftwareSerial(rxPin, txPin);
byte outgoingByte = 0;

void setup() {
pinMode(rxPin, INPUT);
pinMode(txPin, OUTPUT);
rfSerial.begin(2400);
Serial.begin(2400);
}

void loop() {
Serial.println(outgoingByte, DEC);
rfSerial.println(outgoingByte, BYTE);
outgoingByte++;
delay(10);
}
Pretty simple. It just sends the numbers 0-255 repeatedly and prints them out to serial (use the serial monitor to watch the bytes fly by). The part that threw me for awhile was that the receiver has two data pins. I read somewhere (*ahem* SparkFun KLP Walkthrough Tutorial) that only one of them was useful (pin 2) and the other (pin 3) was optional and could be tied to ground. After banging my head against the wall, I looked at the receiver data sheet which clearly shows that the data pins should be tied together! Once I corrected my wiring, it worked beautifully. So, last but not least, a photo.


10 comments:

  1. Totally awesome man! Do any testing on how far apart the links perform?

    I'm totally going to steal this from you and use it for some of my projects :)

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  2. I haven't tried any range tests yet, but I'll be doing some with my first actually use of the transmitters. SparkFun says they're good up to 300 feet (with a 30cm antenna). There's also more to consider when using them than I did for this little test. For instance, using software serial instead of hardware can make life difficult when you're doing more than just a tight loop of receive/print.

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  3. do you need to buy an antena or are the antenas built in

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  4. You'll get better range with an antenna. I believe the data sheet recommends 30cm of wire attached to the antenna pin.

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  5. Tried this, but I just get a completely random string of numbers being received. Any ideas?

    Mike

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  6. Thank you! You save my holidays!
    I was trying to receive the MO-RX3400
    data output using Arduino rx pin (digital pin0) but the Arduino environment interfere; with a osciloscope I knew that both transmitter and receiver were O.K. But when I connect the radio receiver output to Arduino rx pin nothing appear in the Arduino Environment Serial Monitor.
    Last note:
    To help other users:
    The library SoftwareSerial must be included


    Thank you again !

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  7. I'm getting all kinds of random numbers as well. I think it might be because there is no syncing involved between sender and receiver. So if you send a constant stream of information it might work, but I think mine is picking up mid-byte on some of the data I'm sending. More later if/when I figure it out. I'd really rather not have to go through all the complexity of UART stuff to make it work.

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  8. It will definitely give you random data if you're not transferring actively. A simple way to get around this is to send a signature/data/checksum sandwich. It's probably not possible to send data without building some sort of protocol on top. If you want to avoid that, use Xbees.

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  9. my arduino uno says this
    As of Arduino 1.0, the 'BYTE' keyword is no longer supported.
    Please use Serial.write() instead.

    ReplyDelete