Using a sent variable

Hallo everybody,

i am working on a home automation solution using several pro minis, that (in the first step) send data from sensors via 433 RF (VirtualWire) to a transmitter. Everything works perfectly, but I don’t want to send too much obvious data through the network (‘window is open’, ‘window is closed’). Instead I want to use little 4-digit-codes, which the transmitter should ‘decode’ and write a status in the console.

Something like
1234 = Bathroom window is open
9876 = Living room window is closed

The Challenge: I am able to send variables through VirtualWire, but only as char and I don’t know how to convert the char-data back into a variable that can be used to print a status into the console.

I am sending the data as followed:

int windowClosed = 1043;
int windowOpen = 7293;
char msg[24];
sprintf(msg, "%i.%i", windowClosed);
vw_send((uint8_t *)msg, strlen(msg));

At the moment the transmitter reads the data like this:

for (i=0;i< buflen;i++) {

But I want to do something like that:

if ((char *)buf == 1043) {
      Serial.println("The bathroom window is closed");

Of course the ‘1043’ can not be used like that at the moment, because it is still text. Does anyone know how I can convert the digits into a variable again, so that I can use it like in my example?

Thanks for help!

null terminate the string in buffer and use atoi.

You don't need to send character data. Send and receive the integer value directly, like this:

   vw_send((uint8_t *) &windowClosed, 2); //send an int


   msglen = VW_MAX_MESSAGE_LEN;  //need to reset every time
   if (vw_get_message((uint8_t *) &data, &msglen)) // "msglen" should end up as 2 for an int variable

Alright @jremington. Works perfectly! I am thrilled :slight_smile:

But here comes the next challenge: I am now playing around with temperature and humidity. Thanks to your help I am now able to send the sensor-data directly as an integer, like this:

 vw_send((uint8_t *) &temp, 2); //send an int
 vw_send((uint8_t *) &humidity, 2); //send an int

The receiver gets the data and I am able to see it in the serial monitor.

But how can my receiver differentiate between the two variables I sent (temperature and humidity)?
It receives both variables as 'data'.

What's the best approach here?


Send a two element integer array instead.