vw_get_message return false when running motors - arduino

Question

I am using Arduino for the first time, my project consists of RF transmitter connected with arduino UNO and a RF receiver connected to Arduino Mega.
I'm try to send data from transmitter and print it on receiver serial using VirtualWire library and every thing is okey for this receiver code:
#include <VirtualWire.h>
int x=9;
int y=8;
int z=10;
int r=7;
void setup()
{
Serial.begin(9600);
pinMode(x,OUTPUT);
pinMode(y,OUTPUT);
pinMode(z,OUTPUT);
pinMode(r,OUTPUT);
vw_setup(2000);
vw_rx_start();
}
void loop()
{
uint8_t buf[VW_MAX_MESSAGE_LEN];
uint8_t buflen = VW_MAX_MESSAGE_LEN;
if (vw_get_message(buf, &buflen)) // Non-blocking
{
int i;
// Message with a good checksum received, print it.
Serial.print("Got: ");
for (i = 0; i < buflen; i++)
{
Serial.print(buf[i], HEX);
Serial.print(' ');
}
Serial.println();
}
}
Then i add some if statments to run 2 motors (connected to x,y,z,r pins) based on recrived values :
#include <VirtualWire.h>
int x=9;
int y=8;
int z=10;
int r=7;
void setup()
{
Serial.begin(9600);
pinMode(x,OUTPUT);
pinMode(y,OUTPUT);
pinMode(z,OUTPUT);
pinMode(r,OUTPUT);
vw_setup(2000);
vw_rx_start();
}
void loop()
{
uint8_t buf[VW_MAX_MESSAGE_LEN];
uint8_t buflen = VW_MAX_MESSAGE_LEN;
if (vw_get_message(buf, &buflen)) // Non-blocking
{
int i;
// Message with a good checksum received, print it.
Serial.print("Got: ");
for (i = 0; i < buflen; i++)
{
if (buf[i]==0x77)//Stop motors
{
digitalWrite(x,LOW);
digitalWrite(y,LOW);
digitalWrite(z,LOW);
digitalWrite(r,LOW);
}
else
{
if(buf[i]==0x80)//2 motors clockwise
{
digitalWrite(x,LOW);
digitalWrite(y,HIGH);
digitalWrite(z,HIGH);
digitalWrite(r,LOW);
}
if (buf[i]==0x90)//counter clockwise
{
digitalWrite(x,HIGH);
digitalWrite(y,LOW);
digitalWrite(z,LOW);
digitalWrite(r,HIGH);
}
}
}
Now the problem is that when motors is stop working and I am sending the values that will run it either with or counterclockwise the motor works in the right direction but then does not respond to any data sent.
In short, when the motor stops working and I send data, the receiver receives the values and runs the motor violin is required, but then for example if the motor was working clockwise and sent the order which is running counterclockwise or even stop work, it does not respond and continues to move It was.
I noticed that this bacause when motors runs this function returns false
vw_get_message(buf, &buflen)
But i don't no why!

Answer 1

In VirtualWire library every time you send a new character or a set of characters your buffer will be overwritten. So the problem in this program is with your for loop checking. It will work fine if you just use the following
For example if you are sending characters like 'A', 'B' etc then
if (vw_get_message(buf, &buflen))
{
if(buf[0]=='A')
{
//move forward
}
if(buf[0]=='B')
{
//move backward
}
.... and so on
Hope this helps