Receiver Shield seeing data all the time

315MHz and 433MHz wireless connections are very commonly used by consumer electronics including weather stations, home automation remote controls, power consumption meters, car alarms, and also many DIY projects.
mjoconr
Posts: 12
Joined: Sun Dec 25, 2011 12:59 am

Receiver Shield seeing data all the time

Post by mjoconr » Tue Jan 03, 2012 10:09 am

Hi Guys

Would it be normal for me to be seeing data on the Receiver Shield all the time ?

I wrote a program using leading and trailing edge detection and interrupts and see data all the time.

I've attached a copy of the code and the result.

I've sure the code has issues, but I've written a couple of different versions using different methods.

Thanks
Mike

cef
Freetronics Staff
Freetronics Staff
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Re: Receiver Shield seeing data all the time

Post by cef » Tue Jan 03, 2012 11:04 am

Hi Mike,

Looks like the forum wouldn't allow you to attach it when you tried to post.

You have to have made 3 posts before the forum will allow you to attach files. You've now achieved that.

I've checked and you should now have permission to attach files, so feel free to try again.

Sorry about the inconvenience.

mjoconr
Posts: 12
Joined: Sun Dec 25, 2011 12:59 am

Re: Receiver Shield seeing data all the time

Post by mjoconr » Tue Jan 03, 2012 11:40 am

Hi Cef

I'm still unable to attached the file, the site keeps saying that the extension is not allowed.
.log .txt and no extension.

Cheers
Mike

cef
Freetronics Staff
Freetronics Staff
Posts: 106
Joined: Wed Nov 09, 2011 12:53 am

Re: Receiver Shield seeing data all the time

Post by cef » Tue Jan 03, 2012 12:02 pm

Sorry about that Mike. Give it a try now.

Note: Archives and Images were allowed, but Text files were not (there is a list of various file extensions, and they're grouped into various types). I've enabled that for the moment. Will check with Jon on how he wants to handle that longer term.

mjoconr
Posts: 12
Joined: Sun Dec 25, 2011 12:59 am

Re: Receiver Shield seeing data all the time

Post by mjoconr » Tue Jan 03, 2012 12:08 pm

File as mentioned in the topic first message

Mike
Attachments
EdgeChanges.txt
(219 KiB) Downloaded 454 times

mjoconr
Posts: 12
Joined: Sun Dec 25, 2011 12:59 am

Re: Receiver Shield seeing data all the time

Post by mjoconr » Wed Jan 04, 2012 11:18 pm

Ok possibly answering my own post, I suspect that the receivers gain goes wide open when not receiving a signal.
Meaning that most of the pulses I see are just noise.

Ever so often I see in the log a section which is cleaner with the zero's and one's being more consistent. I suspect that this is the transmission from my weather units. The units I'm using transmit a Manchester 'normal' code.

I think I'll move on to trying to decode this and see what happens.

Mike

mjoconr
Posts: 12
Joined: Sun Dec 25, 2011 12:59 am

Re: Receiver Shield seeing data all the time

Post by mjoconr » Sun Jan 08, 2012 4:07 am

Hi All

How likely is it that I could have a bad receiver ?

I see way to much noise and when I do see traffic which is the weather units its way to short and does not come close to meeting the protocol I have from another locations.

I sent an email to the support@freetronic on the 6th, have not seen a reply.

Mike

RAS
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Joined: Tue Jan 17, 2012 4:13 pm

Re: Receiver Shield seeing data all the time

Post by RAS » Tue Jan 17, 2012 4:43 pm

I'm seeing pretty much the same (continuous) activity on the output of the 433Mhz shield I'm using, and also assumed that it's the dynamic gain at work in my relatively noisy environment. Unfortunately, I'm trying to reverse engineer a protocol for an OOK device that only transmits once every 20 seconds or so - sifting through all of the extra bits to find ones that may or may not matter isn't much fun. Doing some data sheet searches, I noticed one that seems to indicate there's another model of the RXB6 that has an analog signal strength indicator (RSSI) on one of the pins. The sheet I saw identified it as a V2.0 (vs the V1.1 that's on the card now). Being able to monitor the signal strength to "window" my search would be a great advantage. Any chance that there could be an upgrade? I wouldn't even mind soldering in an extra line to get the signal to an analog pin, so that could be a user option with the same PCB....

Lacking an update, if anyone has any other suggestions on a better way to isolate the signal with this shield, please chime in...

Thanks - Richard

mjoconr
Posts: 12
Joined: Sun Dec 25, 2011 12:59 am

Re: Receiver Shield seeing data all the time

Post by mjoconr » Tue Jan 17, 2012 9:42 pm

RAS wrote:Unfortunately, I'm trying to reverse engineer a protocol for an OOK device that only transmits once every 20 seconds or so - sifting through all of the extra bits to find ones that may or may not matter isn't much fun.
I can force my weather unit to transmit and I've been doing this and I have the protocol doc. I'm expecting 24 short pulses 349ms in length for the preamble. I never see this.

Mike

RAS
Posts: 3
Joined: Tue Jan 17, 2012 4:13 pm

Re: Receiver Shield seeing data all the time

Post by RAS » Wed Jan 18, 2012 5:35 pm

Experimenting a little last night, I brought the sensor in and set it next to the card, and disconnected the antenna from the card just to limit it's external influences a little. Using an oscilloscope on the data pin, I identified some low pulses at about the right periodicity to be transmissions from the sensor. I've tuned some test code to lock up to those and give me a smaller bucket of bits to examine. I haven't re-tried this code with the sensor back outside and the antenna attached yet, but I should be able to try that in the next day or two.

One thought I had after looking at one of the other forum threads was that some Arduino variants may have worse RF harmonics "in band" (or other EMI characteristics) that are "bad" for these receivers than others. A small sampling in the forum, but It seems like maybe people have had better success with some base cards. As it happens I was running with a Ruggeduino yesterday. I'll try to switch to another board in the next couple days, and also go to battery power rather than USB sourced and see if it makes much difference. Depending on the results I may even try running the card "remote" from the Arduino (power up shield directly from battery and look at its output with the scope). Actually, as I write this, I realize I should probably do that first because it's the easiest and would tell me the most.... If you've got a scope handy that might be the easiest way to tell if you've got a card problem or an integrated problem.

I'll let you know what I see on mine. - R

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