Squibcakes?

Thanks for your reply. I don't think it will solve my problem because:

1. My problem is not achieving reliable communications but achieving a reliable alarm on LOSS OF COMMUNICATIONS.

2. The radio receiver is on a robotic vehicle and the aim is to ensure that the motors are turned off on loss of radio contact.

3. Whilst in radio range my current simple SERIN and WAIT "!" work fine.

4. But when it's out of range the radio receiver passes noise to the PIC and so the RxPin leaves the "idle state" and the "Lost_Signal" code is never activated. And the SERIN command just hangs waiting for a "!" transmission.

A solution would be to:

1. Start TIMER1 and enable interrupts.
2. Wait for a "!" then grab the message then disable interrupts.
3. If TIMER1 overflows and the interrupt occurs - execute the "Lost_Signal" code.

All this is a guess on my part and I'm trying to see if anyone has had some success with reliable "lost communications" routine when the receiver passes noise to the PIC.

If I have misunderstood your suggestion - sorry?

Regards Bill Legge