RF communication

[filjoa]

Hi

I buy this items for try make a little project:
http://www.hobbyengineering.com/CatRFSCODE.html

but if I have one PIC to Transmitter and other for Receiver how I can communicate? on datasheet tell "data" :S

with I simple printf ("Hello Word"); on transmitter I will see on Receiver? or because on datasheet tell communication "data" printf don't work?

kind regards

[FvM]

You can try. I see, that all datasheet circuits are using Holtek enocder/decoder chips rather than UART communication.

There are basically two issues:
- The RF chips are intended for a near 50 % duty cycle baseband signal (Holtek is using 33%/66%), but not for 10-90% with UART
- A synchronisation of the data stream at send start is required

Ideally, you would use manchester encoding, which provides a perfect 50 % duty cycle modulation, and in addition a preamble for initial synchronisation

I've seen sugestions to send a manchester-like modulation with a hardware UART, stretching 8 bits to two UART frames. But synchronisation on receive can't be perfect with this method, particularly when a hardware UART is used.

I would opt for software manchester encoding and decoding.

[filjoa]

Hi

Is easy make this Manchester encoding and decoding?

If is not easy, some one recommend other hardware RF for I buy? Where (for shipping to Portugal)?

kind regards

[filjoa]

Hi

I return to this project, but without success

module RX: http://www.hobbyengineering.com/specs/WENSHING-RWS3716C.pdf
module TX: http://www.hobbyengineering.com/specs/WENSHING-TWSBS3.pdf

Today I try communicate between 2 PICs, the connection stay direct between PIC and module.

But it don't work...

My example program:

On RX PIC:

[Steve H]

Divide and conquer

I suggest that you get the RS232 working with a PC on both sides first. Remember that the RS232 to a PC needs to have an inverter from the PIC to the PC (any number of circuits on the web will show you how to do this).

When you have the PC successfully talking to both PICs - then connect both PIC's together with a wire link and get that working.

Then go to your RF link.

This is how I approach every new problem. Instead of making one big giant leap that is bound to confuse and get horribly messed up, it is usually much better to make small steps toward your goal. You will learn things along the way and your resulting design will be much more robust.

HTH - Steve H.

[filjoa]

Hi

I make all this steps... I only work this way ;)

I think which problem stay on breadboard, I think which it don't work fine at high frequencies.

I go try tomorrow.

[Guest]

It sounds like you think the problem is the RF link... Then go debug the RF link by itself.

Hook up a square wave to the data input on the TX - look at the demodulated RX with a scope - does it look right?

Keep working on the RF link by itself until it works correctly...

Then hook up to the PIC.

HTH - Steve H.