315 Mhz transmitter - Receiver

Projects Programming
1

Hi,

Tonight I plugged in my new 315 MHz Trasmistter - Receiver from Ebay. I finally had them to work, I think.

Here is my code.

TX

#include <VirtualWire.h>


void setup()
{

  pinMode(13, OUTPUT);

  vw_set_ptt_inverted(true);
  vw_setup(2000);            // Bits per sec
  vw_set_tx_pin(3);          //Tx pin
  
}


void loop()
{
  
  delay(500);               //Send a message every half second

  char *msg = "12321";
  digitalWrite(13, HIGH ); // Flash a light to show transmitting
  vw_send((uint8_t *)msg, strlen(msg));
  vw_wait_tx(); // Wait until the whole message is gone
  digitalWrite(13, LOW);


}

RX

#include <VirtualWire.h>


int i =0;


void setup()
{

  Serial.begin(9600);
  Serial.println("Started");
  
  vw_set_ptt_inverted(true); 
  vw_setup(2000);	         // Bits per sec
  vw_set_rx_pin(2);              //Rx pin
  vw_rx_start();               

  pinMode(13, OUTPUT);  

}

void loop()
{


  uint8_t buf[VW_MAX_MESSAGE_LEN];
  uint8_t buflen = VW_MAX_MESSAGE_LEN;

  if (vw_get_message(buf, &buflen)) // Non-blocking
  {
    
    digitalWrite(13, HIGH);
    
    Serial.print('\n');
    Serial.println("Receiving data");
    Serial.print('\n');
    
    for (i = 0; i < buflen; i++)
    {
      Serial.print(buf[i]);

    }
    
    Serial.print('\n');
    Serial.print("------------------------");
    
    
    delay(10);
    digitalWrite(13, LOW);

  }
}

The questions are:

1 - What is that kind of variable : char *msg = "12321";
2 - If I send 12321 and I reveived 4950515049, how to put it back in 12321 format? Is it something like HEX TO INT?

It seem's that 49 is the start and end delimiter for a transmission, am I right? So what are those: 3 = 1 , 2 = 5 and 1 = 0.....

EDIT: I substract 48 from each value so I came back to 12321 I have tested with different value and everything is fine

3 - What are those kind of variable? uint8_t buf[VW_MAX_MESSAGE_LEN];
uint8_t buflen = VW_MAX_MESSAGE_LEN;
I have worked on arduino since a long time now and never seen those type of variable. Could it be replaced with some more common one?

Thanks for the help!

2

The Tx sends characters, as you've figured out.

uint8_t buf[VW_MAX_MESSAGE_LEN];
unsigned 8 bit array called 'buf' that is "VW_MAX_MESSAGE_LEN" bytes in length - if you read the virtual wire documentatio, I think this is 30 bytes.

uint8_t buflen = VW_MAX_MESSAGE_LEN;
unsigned 8 bit variable called 'buflen'. I think 30 bytes unless you change it in pre-setup area:

byte VW_MAX_MESSAGE_LEN = 20;
or maybe there's a library call to make that change.

3

Thanks for the clarifications CrossRoads.

4

Hey guys. I'm rather new to the scene. Where does the line "byte VW_MAX_MESSAGE_LEN = 20;" get inserted? I have replicated the same issue. How do we get the code to match on the receiving board? Thanks