Go Down

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

robtillaart

Quote
This unit sends a short data burst about every 32 seconds.

So the question is, who or what sends it?

Wrap the antenna in alumium foil, does it still send?

The module has a signal strength indicator, so you can use it to detect the sender? (neighbour, TV, elektricity meter, washing machine ...?)
Rob Tillaart

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

Magician


I don't think to wrap antenna or ever ground it will change situation.
Unit will continue transmitting data, whatever noise   it can pickup,
let say it's own input circuitry.
Protocol analyzer, sniffers and other technological "breaking enigma" option is
good, but only for federals with unlimited budgets.

I'd suggest, it'd be easier to decode message that is not a noise, but
something repeatable over and over again.
if it's power monitor, get one more same kind device, that will transmit in close proximity to your monitor, stable power signal over the time.

1). Turn on transmitter, set power that definitely will suppress any environmental garbage.
2). Make a dump of the stream from receiver, or watch it on you serial monitor attentively.
3). Change a  power of your own RF source.
4). Take a second dump, (or don't look around if it stream on serial monitor -):
5). Compare results.
a) If no difference, most likely, bit-rate settings mismatch (receiver and analyzer).
     Change serial settings of the analyzer, go to step 1.
b) if you notice the difference at least in one byte, it could be data-byte RSSI.
     Go to step 3, play around with Tx signal several times, to gather more information.

Hope it will help.





scruss

#7
Feb 22, 2011, 08:21 pm Last Edit: Feb 23, 2011, 04:16 am by scruss Reason: 1

So the question is, who or what sends it?


It's one of these: Electricity Power Cost Monitor.

Quote
The module has a signal strength indicator, so you can use it to detect the sender? (neighbour, TV, elektricity meter, washing machine ...?)


Sort of. The received signal strength peaks every ~31.8s, which coincides with the Power Cost Monitor's display updating. I get signal strength traces like this: http://scruss.com/wordpress/wp-content/uploads/2011/02/signal_strength.pdf

(If that image is blocked, there more of a blog post here: on the trail of the elusive Power Cost Monitor signal)

cheers,
Stewart

robtillaart

The 9600baud looks most promissing, but still makes little sense - is 19200 and 38k4 log also possible?
Rob Tillaart

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

scruss


The 9600baud looks most promissing, but still makes little sense - is 19200 and 38k4 log also possible?

I don't think so. The Parallax receiver only supports up to 9600. Most 433MHz wireless rx/tx units go up to 2400 or 4800.

Go Up