RX TX modules - intermitent communication

[dhouston]

See my response in this thread http://www.picbasic.co.uk/forum/showthread.php?t=11285.

[ruijc]

Greetings dhouston,

thanks for the help!

I read your article and the Demo code.
To be honest i didn't understood some of the lines in the code and a bit of the article( being English as NOT my native language and just starting to learn comm/protocols and stuff...doesn't help ).

In your demo code you use Pulsin instead of Debugin or Serin and this makes me get confused.

I was looking for a simple approach where i could use the debugin/HSerin instructions.

Is there any other way for this to work ?

Thanks

[dhouston]

@ruijc

I have added examples that use SerOut2 and SerIn2 but I have not tested these as I'm rather busy with a project of my own right now. They should be easier to follow.

The problem with using $55 or $AA (or a string of several) is that the receiver has difficulty distinguishing them from the normal noise it sees in the absence of a signal. Using a long pulse followed by a space (about half the length of the pulse) sets the receiver AGC and gives the receiver an easy to distinguish marker for the start of a transmission. Keeping communications packets short will help maintain DC balance

[ruijc]

Thanks dhouston,

The Serin/Serout version looks good thanks

I understand your explanation for the Pulsout.

If i understood correctly... the problem is for the RX module distinguish the Data from noise, correct ?

Since the RX module will "see" the data transmition with the pulsout trick and grab it, after processing internally, it should give the message correctly to the pic.

Then why the Receiver pic needs to "Pulsin" the RX module?

I'm looking forward to test the SerIn version tonight

[dhouston]

Then why the Receiver pic needs to "Pulsin" the RX module?

In effect, the receiver code waits for a pulse of sufficient length then calls SerIn2 to catch the message that follows the intervening space. IOW, the pulse is seen as a "start of transmission" marker by the receiver

[ruijc]

Thanks for your time dhouston.

I've tryed the Serin2/Serout2 version but i couldn't receive any message

Since my modules work at 19200 i changed the code like ( the rest is the same as you posted ):

TX

SerOut2 tx,16416,["HELLO",10]

RX

SerIn2 rx,16416,[STR msg\5\10]
lcdout cl,row4, "received - ",STR msg\5

[dhouston]

I guess I should have looked at the datasheet for your modules but, based on your code in the first post, assumed they are ASK - they are FSK which changes things a bit. See Data Reception on p5 of the link you gave.