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RF Transmitter / Receiver Problems

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jackprestonuk

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Hi guys (first post)
I have a problem setting up a simple pair of RF transmitter/receivers (here's the datasheets; Transmitterand Receiver)

I've got an RS232 connection from my pc set up through a max232 chip, putting out reliable serial data (I've checked this by reading it back INTO my computer again and monitoring). I've wired up the transmitter as the datasheet says - taking the output from my max232 into the data in pin of the transmitter. My problem is that nothing is being received at the receiver (also wired as stated).

I don't have an oscilloscope to test the transmitter's antenna pin, but nothing else I connect to it on the offchance (like LEDs etc) seems to be getting anything on that pin, so I'm worried that no radio signal is coming out of the transmitter...

Any help? Has anyone used modules like this before?
Thanks
 
Could you be more specific? Are you saying the the 0-5V UART output from the max232 is not suitable? In that case, what does the datasheet mean when it says the module can handle CMOS/TTL input?

As for the Manchester encoding, is this something I should just do in software in, say, a uC, or do I need separate specialised encoders/decoders? Sorry if these are stupidly basic questions...
What kind of voltage signal should it be once Manchester encoded, and what makes it more usable by a radio module than a standard UART (or, why is this UNsuitable?) I'm really very new to the radio electronics thing...

Thanks!
 
No, I'm not. The voltage levels are fine.

The Manchester encoding and decoding is something you can handle in software, yes. A forum member here has a tutorial on the subject that might be helpful to you
 
Ah I see - so you're saying it's the fact that my serial information at present doesn't make enough frequent transitions from low to high that's the problem in using it for RF? Thanky for your help, I'll check out that tutorial - looks very handy!
 
Could you be more specific? Are you saying the the 0-5V UART output from the max232 is not suitable? In that case, what does the datasheet mean when it says the module can handle CMOS/TTL input?

As for the Manchester encoding, is this something I should just do in software in, say, a uC, or do I need separate specialised encoders/decoders? Sorry if these are stupidly basic questions...
What kind of voltage signal should it be once Manchester encoded, and what makes it more usable by a radio module than a standard UART (or, why is this UNsuitable?) I'm really very new to the radio electronics thing...

Thanks!

If you check my PIC tutorials, there's one that explains why you need to use Manchester coding (or similar).
 
Thanks Nigel, I'm having a read through your RF tutorial now! Very helpful! So if I set things up so that I have a 0-5V Manchester encoded signal, I can pipe that into the data IN on my radio transmitter, and that should be able to handle that? Then I can just decode the Manchester on the other end.
 
Thanks Nigel, I'm having a read through your RF tutorial now! Very helpful! So if I set things up so that I have a 0-5V Manchester encoded signal, I can pipe that into the data IN on my radio transmitter, and that should be able to handle that? Then I can just decode the Manchester on the other end.

Yes, RF Solutions even sell ready made encoder/decoder chips that do everything for you (don't get confused by the Holtek or Motorola 'encoder/decoder' chips which are crude remopte control chips, not data ones).

Check out:
 
Ah I see! My problem with something like that is this; if I was to use that chip to convert RS232 to Manchester encoded data, then send that over radio to multiple devices, then each end device would presumably have to be able to convert RS232 into a PIC-usable logic voltage as it came from the device's radio receiver?
So my question is; if I had something like that, converting RS232 to Manchester encoded data, and sending it out, and then another transceiver chip at the other end taking data from the radio receiver, would THAT chip output the RS232 data again, or would it churn out more usable logic?
Very confusingly asked question, sorry lol!
 
Never mind, got confused! I think I'm right in thinking that any RS232 to serial conversion (say like that done in a max232) is to be done before sending data to the Manchester-encoder-chip? So then at the other end, the Manchester-decoder also outputs nice serial data... Correct me if I'm wrong lol please
 
Never mind, got confused! I think I'm right in thinking that any RS232 to serial conversion (say like that done in a max232) is to be done before sending data to the Manchester-encoder-chip? So then at the other end, the Manchester-decoder also outputs nice serial data... Correct me if I'm wrong lol please

MAX232's invert the data, so you would use one to connect to a PC (as that's how the encoder/decoder is designed), you wouldn't need one for direct connection to a PIC, as that would require a MAX232 to connect to a PC as well, so it's the correct polarity already.
 
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