RF Link problems...

nuno12345 · Joined: 16 Jul 2008 Posts: 50

Hello all...
I acquired both sparkfun WRL-08948 receiver and WRL-08945 transmitter.

My problem is in their communication...

I'm able to communicate with PC using MAX232...

As soon as I connect my transmitter to PIN_B5(TX) my computer stops reading anything....the problem is that if I connect MAX232 pin11 to my receiver it doesn't get anything either :/.

nuno12345 · Joined: 16 Jul 2008 Posts: 50

Anyone?

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Guest · Posted: Tue Feb 24, 2009 10:03 pm

Well...I use a PIC to transmit data...and receiver+MAX232 to get data...something like:

PIC----->transmitter
receiver-->MAX232

So, the receiver doesn't connect to the PIC, only transmiter...

Thanks PCM ;)

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

I haven't used these RF Link modules. Sparkfun has some links for
application help. Here's one of them, which uses an AVR micro instead
of a PIC:
http://winavr.scienceprog.com/example-avr-projects/running-tx433-and-rx433-rf-modules-with-avr-microcontrollers.html

Notice his comments on sending a sync byte, before the real data byte
is sent. I think you should do this.

Also, look in the MO-SAWR-A transmitter data sheet, which is available
on the Sparkfun site:
http://www.sparkfun.com/datasheets/Wireless/General/MO-SAWR.pdf
It says the typical turn-on time for the transmitter is 20 ms. Also look
at the receiver data sheet:
http://www.sparkfun.com/datasheets/Wireless/General/MO-RX3400.pdf
It has a typical turn-on time of 30 ms.

The receiver may already be "turned on" because it's on another board
which is connected to your PC. But I assume that the transmitter is
on the same board as your PIC. Therefore, you need to add a delay
at the start of main() in your PIC transmitter source code. Example:

Guest · Posted: Thu Feb 26, 2009 3:09 pm

still nothing :/

Ill give more info...

Receiver:
My receiver's digital output is connected to pin 11 of MAX232N (tried both analog and digital outputs). both 3 GND's are shorted, same for both +5V, both connected to GND and +5V.

MAX232N:
4 capacitors, all 1uF 63V, 1 connected to pin +1-3, other +4-5, other from pin +2 to VCC, from 6 to +VCC.
(+ indicates the positive of the capacitor)
Pin 16 to VCC, 15 to GND, 14 to RxD (serial port).
Pin 11 to receiver.
0V from serial to GND.
(it may look a bit complicate but its the typical connection, and it works, just doesnt work with the RF receiver, problem must be in the receiver).

Transmiter:
GND to GND, +5V to VCC, DATA to PIC'c pin b5.

Im not using any antennas, but i tried with antennas, still no luck...

Im using the same protoboard for both transmiter, receiver, MAX232 and PIC.

Im using the same "power source" for all 4...
My power source comes from an usb port at the same computer where the serial cable connects to. (cool thing is that I dont need GND pin from usb, since its shared, but im using it anyway).

Thanks

PCM programmer · Joined: 06 Sep 2003 Posts: 21708

Try the Sparkfun RF Link forum:
http://forum.sparkfun.com/viewforum.php?f=13

Notice the comments about the sync bytes in this post:
http://forum.sparkfun.com/viewtopic.php?t=12676

This post suggests sending sync bytes, then send the data byte, then
send the complement of the data byte.
http://forum.sparkfun.com/viewtopic.php?t=11683

I didn't see any posts about your modules, but that forum is probably
your best bet.