LowPowerLab Forum

I am trying to use 2 RFM69HCWs to send sensor data from the HC-SR04 to each other. However, I  realised that the data sent might not necessarily be the correct data. I have attached the codes for the receiver and the transmitter side :

For transmitter


#include <RFM69.h>
#include <SPI.h>
int tri = 9;
int echo = 8;
float Micro, sec;
int cm;
float cmps;
float mps = 342.5;

#define NETWORKID     0   // Must be the same for all nodes
#define MYNODEID      1   // My node ID
#define TONODEID      2   // Destination node ID

// RFM69 frequency, uncomment the frequency of your module:

#define FREQUENCY   RF69_433MHZ
//#define FREQUENCY     RF69_915MHZ

// AES encryption (or not):

#define ENCRYPT       true // Set to "true" to use encryption
#define ENCRYPTKEY    "TOPSECRETPASSWRD" // Use the same 16-byte key on all nodes

// Use ACKnowledge when sending messages (or not):

#define USEACK        false // Request ACKs or not

// Create a library object for our RFM69HCW module:

RFM69 radio;

void setup()
{
  // Open a serial port so we can send keystrokes to the module:

  Serial.begin(9600);
  pinMode(echo,INPUT);
  pinMode(tri,OUTPUT);

  // Initialize the RFM69HCW:

  radio.initialize(FREQUENCY, MYNODEID, NETWORKID);
  radio.setHighPower(); // Always use this for RFM69HCW

}

void loop()
{
  digitalWrite(tri,HIGH);
  delayMicroseconds(10);
  digitalWrite(tri,LOW);

  Micro = pulseIn(echo,HIGH);
  sec = Micro*pow(10,-6);

  cmps = mps*100;
  cm = cmps*(sec/2);
  Serial.println(cm);
  delay(500);
  static int sendlength = 2;

 
       radio.send(TONODEID, cm, sendlength);

     
   
 

}



For receiver :


#include <RFM69.h>
#include <SPI.h>

#define NETWORKID     0   // Must be the same for all nodes
#define MYNODEID      2   // My node ID
#define TONODEID      1   // Destination node ID

// RFM69 frequency, uncomment the frequency of your module:

#define FREQUENCY   RF69_433MHZ
//#define FREQUENCY     RF69_915MHZ

// AES encryption (or not):

#define ENCRYPT       true // Set to "true" to use encryption
#define ENCRYPTKEY    "TOPSECRETPASSWRD" // Use the same 16-byte key on all nodes

// Use ACKnowledge when sending messages (or not):

#define USEACK        false // Request ACKs or not

// Create a library object for our RFM69HCW module:

RFM69 radio;

void setup()
{
  // Open a serial port so we can send keystrokes to the module:

  Serial.begin(9600);

  // Initialize the RFM69HCW:

  radio.initialize(FREQUENCY, MYNODEID, NETWORKID);
  radio.setHighPower(); // Always use this for RFM69HCW

}

void loop()
{

  if (radio.receiveDone()) // Got one!
  {
    // The actual message is contained in the DATA array,
    // and is DATALEN bytes in size:

    for (byte i = 0; i < radio.DATALEN; i++)
      Serial.print((int)radio.DATA[i]);

    Serial.print("\n" );
  }
}



In the attached picture, COM5 is the transmitting side (with the HC-SR04) and COM3 is the receiving side. As observed, there isn't same data being received. Can anyone help me on this?Thanks!

On the transmit side, change the send command to:


radio.send(TONODEID, &cm, sendlength);   // NOTE: need to use address of 'cm'


On the receive side, I would change the code to:

  if (radio.receiveDone()) // Got one!
  {
    // The actual message is contained in the DATA array,
    // and is DATALEN bytes in size:
    // NOTE: each element is an int (2 bytes), so need to recast the data as such...
    int *pData = (int*)radio.DATA;

    for (byte i = 0; i < radio.DATALEN; i+=2)
      Serial.print(*pData++);

    Serial.print("\n" );
  }


Tom

Could you send an integer array instead of the cm variable to transmit more variables?