433mHz Transceiver Intermittant data - help!?

xanatos

I am using two brand new 433mHz TX/RX pairs and attempting to run the code that I downloaded from the products' page (also attached).· The code tokenizes just fine and loads.· The transmit side debug window repeatedly reports "Sending Packet 1", approximately every second.· The Receive side shows NOTHING usually, but occasionally I will get a small piece of data... just a snippet of the message contained in the TX side's EEPROM data as "Message".· The output of the receiver debug window appears as:

Parallax producParallax producParallax producParallax pr
oducParallax producParallax producParallax producParalla
x producParallax producParallax producParallax producPar
allax producParallax producParallax producParallax produ
cParallax producParallax producParallax producParallax p
roducParallax produces our own RF mes our own RF modules
·from proodules from proodules from proodules from prood
ules from proodules from proodules from proodules from p
roodules from proParallax producParallax produces our ow
n RF modules from proParallax producParallax produc· **
RECEIVE ERROR **··· ** RECEIVE ERROR **· Parallax produc

This code represents the RX side's output window after several dozen resets.· The RECEIVE ERROR showed up after I removed power to the TX side and re-applied.

I have the "transmit" and "receive" stamp boards separated by anywhere between 2 and 5 feet at the moment, so there shouldn't be any problem with too much distance!

The only changes I made to the code in the demo programs was to change the pin assignments from pins 13, 14 and 15 on each stamp to pins 11, 12 and 13 as I have plans for pins 14 & 15.· Also - I am running a BS2 on the receiver and a BS2SX on the transmit side.

Has anyone else experienced similar issues with these?

Thanks for any help, truly!

Dave X

xanatos

PS., I have tried switching the two systems - made the TX side into the RX side & vice versa - identical results. Highly confuzzled...

Dave

W9GFO

You are only receiving 15 characters and this line appears in the TX code;

IF (strLen = 15) OR (char = EOM) THEN EXIT ' Exit if done

Oh, but I see sometimes you are receiving more than 15. Sorry, maybe that would have been just too easy.

Rich H

xanatos

That IS interesting - the most oft repeated section of teh data IS 15 characters long "Parallax produc".· But - as you noted - I DO get other chunks, some larger tahn 15 characters.

A bit more info - if I use the TX and RX ONLY code (not transceiver code, just one uncorrected TX and one uncorrected RX on the other side, I DO get data.· Error-ridden data, but it is there.· I have included THOSE code pairs as attachments as well.· Frustrating when these things don't work out of the box! :-)

Dave

W9GFO

If you are using example code from Parallax and have only changed pin assignments (correctly) then the problem must be somewhere else. A picture of your setup would be helpful for others to see how your system is put together. Wish I could be more help but I don't have any experience with RF modules.

Rich H

Jonathan

Is there any chance you have another device working at 433mHz around? I once had a wireless thermometer that was interfering with the Parallax RF modules.

Have you tried lowering the baud rate? Are the power supplies for both TX and RX good? Are you on a breadboard? If so, try some .1uF caps on the power pins of the modules. Have you tried just sending and receiving a single character?

If you are using wall warts for power, try a battery. Maybe a really dirty power supply? What happens if you just remove the RF units and jump a wire between the two stamps instead?

Jonathan


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www.madlabs.info - Home of the Hydrogen Fuel Cell Robot

xanatos

I'll look around for other devices but the thermometer I have is on 2.4gHz - as are most of my local wireless devices. Is there a minimum separation distance that the transceiver pairs have to have from each other?

I can't post a photo at the moment as I'm heading out the door - but the chances are that if the non-error correcting code works but the error correctng code doesn't... if it was circuit wiring the non-correcting code would not work either. I will try the caps across the power terminals - I am using a breadboard, but I don't think the dtaarate would be high enough to need to worry about interconnect capacitance, and the RF section is entirely contained on the module - including the antenna, so no RF leakage from contact capacitance there either.

Anyone have any other ideas? Especially anyone who has used these items with success??

Thanks very much!

Dave X

Jonathan

Do you have access to a scope? You can look for interference, perhaps you have a neighbor flooding you? Did you check the power supplies and/or try running them on a battery? Try hooking up just the modules to a battery and manually sending the TX pin high/low and see if it is mirrored on the RX side.

I've always seen some hash with these units on the scope. Do you ever get garbage on the debug if you are not transmitting? Are you close to a CRT or any other device that could be making noise?

I've used these items many times with success, so I would guess it's not the units themselves.

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www.madlabs.info - Home of the Hydrogen Fuel Cell Robot

Chris Savage

As a note I was building a test rig for my previous car using our 433 MHz system and had nothing but trouble getting it to work. But when I used the 912 MHz radios it worked fine. Turns out my alarm system on the car was 433 MHz and constantly sent out status information to the alarm pager module on my keychain. This could easily be seen using a scope to watch the RX pin when the transmitter was idle. Here I was receiving this nice strong radio signal in periodic bursts. Enough to mess up my original idea.

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Chris Savage
Parallax Engineering

xanatos

Thanks Chris, and everyone who had an idea. I decided I wanted overkill and went with a solution that specified a 15 mile LoS range, 3000' indoor/urban/industrial. (PM me if anyone wants to know the exact item). Now I should have no problems with 500'! Thanks for the suggestions/ideas. At least now I have a very complete idea of what RF energy is floating around my home office... I borrowed an old 24gHz spectrum analyzer and saw it all! I never knew how much RF my printer puts out! I should have used the analyzer and watched as the video carriers for the local analog TV broadcasts all dropped forever! LOL!

Dave

Chris Savage

Yeah, unfortunately if you have noise on the frequency a product operates at, it is sometimes difficult to operate that product around the noisy environment. I once tested some 2.4 GHz wireless modules. They picked up noise from our several wireless network access points. Finally I switched to a 912 MHz version from the same manufacturer and it worked perfectly.

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Chris Savage
Parallax Engineering