433Mhz Transmitter/Receiver Problems! Help!

rfman78

Hi Group,
I'm having problems with the 433Mhz transmitter and receivers from Parallax.· I'm getting all kinds of interference.

My program just sends numbers over from 0 to XXXXX· and the receiver just gets that data and displays it on the debug terminal (attached via the USB CABLE).

Problems I am having:·
1) Even when the transmitting BS2 is powered· off, the receiver is still getting random data, (continuous data). I tried putting a resistor between Pin7 & data, and this still didn't help
2) I'm just broadcasting numbers from 0 to whatever, and incrementing by 1.· However , sometime after 100, it starts incrementing by 2!!! Even the code only says x = x + 1 and y = y +1

Please help.
The code is listed below:

TRANSMIT CODE

x var Word
y var Word

DO
pulsout 8, 1200
SEROUT 8,16468, [noparse][[/noparse] "!", x.HIGHBYTE, x.LOWBYTE, y.HIGHBYTE, y.LOWBYTE ]
x = x + 1
y = y + 1
pause 10
LOOP


Receive Code
x· var Word
y var Word

DO
LOW 0
SERIN 7, 16468, [noparse][[/noparse]WAIT("!"), x.HIGHBYTE, x.LOWBYTE, y.HIGHBYTE, y.LOWBYTE]
HIGH 0
DEBUG ? x
DEBUG ? y

LOOP

Post Edited (rfman78) : 7/17/2007 6:13:52 PM GMT

SSteve

I don't know about the random data, but missing every other transmission could be because the receive code is still executing the DEBUG statements when the transmit code has begun another transmission. Try putting a PAUSE before the LOOP in the transmit code.

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OS-X: because making Unix user-friendly was easier than debugging Windows

links:
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Our album on the iTunes Music Store

rfman78

whoops.

I forgot to show the pause 10 command, which i do have. And as I said, it works fine , until about 101, 102 at which point it starts incrementing by two.

For the interference, it only happens when the USB Cable is plugged into the computer. But thats the only way I can monitor the Debug statements......

Mike Green

1) Make sure you have a good ground connection between the receiver and the Stamp. That's often a source of noise.

2) Like most "unlicensed" radio bands, the 433MHz band is shared with other devices like garage door openers and wireless burglar alarms.
That might be one source of noise when the transmitter is off.

SSteve

rfman78 said...
I forgot to show the pause 10 command, which i do have. And as I said, it works fine , until about 101, 102 at which point it starts incrementing by two.

Try a higher PAUSE value. When you get to 100, the DEBUG statements take longer because there are more characters being displayed.

▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
OS-X: because making Unix user-friendly was easier than debugging Windows

links:
My band's website
Our album on the iTunes Music Store

rfman78

Hi Mike,

The problem only rears its head when the USB cable is plugged in.· Is there any way that cable or the laptop could be causing that random interference, and is there anyway I can get around that? Ie some kind of small filter circuit I can build in the· dev. board?

Mike Green

If the "interference" only shows up when the USB cable is plugged in, maybe there's conducted RF noise from the computer. If you have some ferrite RF choke cores, you could throw a couple of turns of USB cable through one just past the plug into the computer. Radio Shack sells one with an opening that should be large enough for 3-4 turns of a typical USB cable.

Here: www.radioshack.com/product/index.jsp?productId=2103979&cp=2032058.2032230.2032273&parentPage=family

Post Edited (Mike Green) : 7/17/2007 6:28:46 PM GMT

Larry~

Here is what I have had to do for RF work

use a .1 uf cap from stamp to Rf unit, I found the rf unit I was using held about .25 to .5 volts high when not sending.

depending on the mode of transmission use a resistor from rf unit to ground or +5 this holds the rf unit high or low depending on mode and does not allow floating.