16F628A Serin timeout and Timer1

[Dwayne]

Hello Andrew,

I am not sure if I fully understand your problem, but let me throw this out to you...

The SerIn has two things that can help you...

The Wait until and the timeout.

I am assuming that the ["A"] (wait until "A" is received, then get the next character) is causing your probem.

To help get rid of noise, you need to ground the pin with a resister.

The timeout can be pointed to the place you want to go if no signal is received.

Serin InputPin, T300, 500, Label,["A"],DataStorage

500 millisecond timeout and goto Label.

if ok, put data in DataStorage and continue on.

What I am not sure about, is if Serin is in receive mode, and is receiving data (good or bad) whether that 500 milliseconds will operate or not. I have not tested it, and I didn't see it in the manual. But I want to assume it is operating.

Are we on the same page?

Dwayne

[Rubicon]

Dwyane

Thanks for the reply and sorry for my lack of clarity. I really must post when I'm fresh and not so late at night.

I have the Serin wait and the timeout with a pullup resistor and they work fine with the exception that when the receiver is in fact receiving something the timeout fails. I understand that this is just how it is when using the timeout in Serin. Its essentially the same as if you don't have a pull-up/pull-down resistor to eliminate noise - the transducer line/power supply/component noise with high opamp amplification keeps retriggering the timeout.
SERIN PORTB.0,T300,200,NOSERIN,[CODE],B9

As the receiver is ultrasonic (currently using a 40Khz transducer) I've found that there are many things that emit ultrasonics at or close to that frequency, enough anyway to keep the PIC Serin timeout retriggering. For instance a previous computers power supply two rooms away from the reveiver kept its Receive Indicator LED flickering and the timeout from working. An additional problem is that a transducer will resonate most easily at a particular frequency, 40kHz for example but it'll also resonate at other frequencies just not as easily - a good cause for me to investigate bandpass filters!

This is why I'm after a way other than the program cycle to keep a time count and to turn the receiver off to save battery power when stuck in the Serin timeout.

Do you think the Timer1 part of my first post is a viable option?

Andrew.

[BigWumpus]

Hello,

forget the timeout-option in "serin" when you receive rf-transmissions.

I've build it like this:
I use Timer1 to measure a timelimit.
So, start Timer1,
Repeat receive 1 character trough serin,
if the character is your lead-in receive the rest,
until timer1 ends.
go sleep....

It may be necessary to slow down the transmitter by using DEFINE CHAR_PACING 1000 because you are using slow software rather than fast hardware!

For me it it not necessary to receive each transmission!

[Rubicon]

Thankyou all for your help.

As the transmitter is only sending the qualifier byte and a single code byte over and over at 300bps I'll drop the Serin timeout and give the Serin Timer1 timeout option a go this weekend.

Once again thanks.

Regards,

Andrew.

[BigWumpus]

Think about some leading bytes ($55) in order to syncronize the receiver...