Virtual Wire String, Char array help

Forum 2005-2010 (read only) Software Syntax & Programs
1

Hey guys,
im working on a project to control two servos connected to the receiver arduino by 2 pots connected to the transmitter arduino.

I wanted to start by transmitting two 3 digit numbers across which would ultimately be stored as ints.
for now im just trying to send 2 of the same "Count" integer over separated by a comma.

This is the first time I've worked with the char data format and i need some guidance. Im totally lost trying to figure out how to combine these two ints along with a comma to be sent over. So far all i have is the int "count" being received.

coul someone point me in the right direction :-[
Thanks guys

Heres the code

Transmitter

// Transmitter V0.1
// V0.0 - Transmit string to receiver 
// V0.1 - Transmit count string to receiver

#include <VirtualWire.h>
#undef int
#undef abs
#undef double
#undef float
#undef round
int count = 0;
char *msg;
char num1[3];

void setup()
{
    vw_set_ptt_inverted(true);
    vw_setup(4800);
    vw_set_tx_pin(3); // Transmitter Data Pin
}

void loop()
{
  count++;
  itoa(count, num1, 10);
  char *msg=num1;
  vw_send((uint8_t *)msg, strlen(msg));
  vw_wait_tx();
  delay(50);
  if(count == 999)
  {
    count=0;
  }
}

Receiver

// Receiver V0.1
// V0.0 - Receive string from transmitter then print string on serial port
// V0.1 - Receive string from transmitter, save in "received" string then print "received" string

#include <VirtualWire.h>
#undef int
#undef abs
#undef double
#undef float
#undef round
char received[100];

void setup()
{
    Serial.begin(9600);    
    vw_set_ptt_inverted(true);    
    vw_setup(4800);
    vw_set_rx_pin(23); // Receiver Data Pin
    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))
    {
    int i;
    for (i = 0; i < buflen; i++)
      {
        received[i]=buf[i];
      }
    Serial.println(received);
    }
}
2

for now im just trying to send 2 of the same "Count" integer over separated by a comma.

Want to show me where in this code that is happening?

  count++;
  itoa(count, num1, 10);
  char *msg=num1;
  vw_send((uint8_t *)msg, strlen(msg));
  vw_wait_tx();

Since num1 is an array that can hold 3 characters, any 3 digit value is going to overflow. 100 ==> '1', '0', '0', NULL. That's 4 characters.

3

Thanks for the reply paul,
I figured it all out last night,
Didnt realise a null character had to be included in the char array.
i also figured out how to add char arrays together to be sent to the receiver. I have two analog pot readings being sent to the receiver which then controls the two servos and all is working well.
The only problem is that movement of the servos is a little delayed.
Is there anything i can try that will result in a quicker response

4

Without seeing your sender and receiver code, it's hard to know where the delay is coming from. So, it's hard to recommend specific fixes.

In general, though, you want to transmit at the highest speed that does not result in excessive data loss, and you want to avoid delay() like the plague.