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Topic: Deciphering an unknown serial feed (Read 1 time) previous topic - next topic

scruss

I'm trying to decode the serial wireless transmission from a 433MHz power monitor. This unit sends a short data burst about every 32 seconds. I can see data coming in, and using the Parallax 433 MHz RF Transceiver, I can filter out noise and have a fairly good idea when the data's coming in.

Unfortunately, I have no idea of the bitrate, or whether the bits are inverted, or what's being transmitted. Is there any way that, by looking at a bit stream, for me to know if I'm using the right bitrate?

Thanks in advance,
Stewart

Graynomad

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Is there any way that, by looking at a bit stream, for me to know if I'm using the right bitrate?

Logic analyser, scope, one of the serial sniffers around.

Failing that just start trying different options (although if you don't know what data to expect it will be hard to know when you get it right).

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or whether the bits are inverted,

Is this RS232 or 5v logic signal?

Measure the voltage during the 32sec idle period to determine the polarity. That will remove one variable.

______
Rob

Rob Gray aka the GRAYnomad www.robgray.com

robtillaart

The datasheet - http://www.parallax.com/Portals/0/Downloads/docs/prod/rf/27982-433MHzRFTransceiver-v1.1.pdf - talks about asynchronous serial @ 1200 - 9600 bps
so you need to try 1200, 2400, 4800 and 9600 baud . The code samples all use 2400 baud so that's the one I would start with.

Rob Tillaart

Nederlandse sectie - http://arduino.cc/forum/index.php/board,77.0.html -
(Please do not PM for private consultancy)

scruss


Is this RS232 or 5v logic signal?

Measure the voltage during the 32sec idle period to determine the polarity. That will remove one variable.


It's wireless, Rob. There isn't any idle period, as the antenna picks up anything it can use and turns it into characters.

thanks,
Stewart

Graynomad

Oops, yes you did say wireless.

______
Rob
Rob Gray aka the GRAYnomad www.robgray.com

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