433 mhz reciever problem

Projects Programming
1

I want to blink an led on receiver end according to message received. LED must be switch on when message received is "obstacle absent". But led doesn't switch on whatever be the message received. But serial monitor of receiver shows the correct output. What is problem in code?

here is my code

#include <VirtualWire.h> 
 byte message[VW_MAX_MESSAGE_LEN]; // a buffer to store the incoming messages 
 byte messageLength = VW_MAX_MESSAGE_LEN; // the size of the message 
 int LED =13;
 int pin=11;
 void setup() 
 { 
 Serial.begin(9600); 
 Serial.println("Device is ready"); 
 // Initialize the IO and ISR 
 vw_setup(2000); // Bits per sec 
 vw_rx_start(); // Start the receiver 
 pinMode(LED,OUTPUT);
 } 
 void loop() 
 { 
   char message[VW_MAX_MESSAGE_LEN + 1]; 
 if (vw_get_message(message, &messageLength)) // Non-blocking 
 { // Existing start of if body
   message[messageLength] = '\0';

   if(strcmp(message, "obstacle absent") == 0)
   {
     
   }
 { 
 Serial.print("Received: "); 
 for (int i = 0; i < messageLength; i++) 
 { 
 Serial.write(message[i]); 
 } 
 Serial.println("");
 
 delay(200); 
 } 
 }
 }
2 
if(strcmp(message, "obstacle absent") == 0)
   {
     
   }

The if block is empty. What are you expecting? digitalWrite(LED, HIGH) will turn the LED on, how do you plan to turn it back off, later?

3

sorry but this is my code. The problem is that led is not switch off again when obstacle is present. But led should be switch on when obstacle is absent and switch off when obstacle is present.
What is problem in code. Please help me.

Here is my code

 #include <VirtualWire.h> 
 byte message[VW_MAX_MESSAGE_LEN]; // a buffer to store the incoming messages 
 byte messageLength = VW_MAX_MESSAGE_LEN; // the size of the message 
 int LED =13;
 int pin=11;
 void setup() 
 { 
 Serial.begin(9600); 
 Serial.println("Device is ready"); 
 // Initialize the IO and ISR 
 vw_setup(2000); // Bits per sec 
 vw_rx_start(); // Start the receiver 
 pinMode(LED,OUTPUT);
 } 
 void loop() 
 { 
   char message[VW_MAX_MESSAGE_LEN + 1]; 
 if (vw_get_message(message, &messageLength)) // Non-blocking 
 { // Existing start of if body
   message[messageLength] = '\0';

   if(strcmp(message, "obstacle absent") == 0)
   {
      digitalWrite(LED,HIGH);
   }
    if(strcmp(message, "obstaclepresent") == 1)
    {
       digitalWrite(LED,LOW);
    }
 { 
 Serial.print("Received: "); 
 for (int i = 0; i < messageLength; i++) 
 { 
 Serial.write(message[i]); 
 } 
 Serial.println("");
 
 delay(200); 
 } 
 }
 }

   if(strcmp(message, "obstacle absent") == 0)
   {
      digitalWrite(LED,HIGH);
   }
    if(strcmp(message, "obstaclepresent") == 1)
    {
       digitalWrite(LED,LOW);

}

4

Try this.

if(strcmp(message, "obstacle absent") == 0)
   {
      digitalWrite(LED,HIGH);
   }
   else   
   {
       digitalWrite(LED,LOW);
   }
5

Or the much simpler:

  digitalWrite (LED, strcmp(message, "obstacle absent") == 0) ;

since the argument to digitalWrite can be a boolean - HIGH is true and LOW is false...