Jdy40 Arduino Example Best -

Serial.println("JDY-40 Master/Slave Ready");

Out of the box, the JDY-40 works. But to eliminate interference and maximize range, you must configure it via AT commands.

void setup() Serial.begin(9600); // For debugging via USB jdy40.begin(9600); // JDY-40 default baud rate

// Parse your data here if (receivedData.startsWith("TEMP:")) // Extract and act on data receivedData = ""; else receivedData += c;