Programming idea for use with scanners

[xoclipse]

Hey everyone, I'm new to the forums, just got myself a PRO-97 scanner from Radio Shack, and have been loving every minute of playing with it.

While I was messing with the signal stalker feature, I put my garage door opener close to it to see if it the scanner could pick it up. I found out the garage door opener transmits at 390.00Mhz, and tuned my scanner accordingly. When I pressed the button on the garage door, I could hear the little data bursts through the scanners speakers.

This gave me the idea of writing a program to decode these little "data bursts", to find out the actual code the opener sends. I have an older garage door, before rolling codes came around. My opener has 12 dip switches in the back of it, which match up to the actual garage door mechanism in the garage. I figure I should be able to decode the signal the opener sends to retreive the values of each dip switch.

I hooked up the headphone output to my computer, and did a little analysis of the waveform, and I'm pretty sure it uses ASK(amplitude shift keying). Soon I'm going to add the discriminator output to the scanner so I can get a little more precise of a waveform.

So right now I'm working on writing a C++ program using Microsoft's Multimedia API to get the input from the scanner and see if I can decode it and display the code the garage opener sends. If anyone is interested in helping me, or has any resources for programming this kind of application, please let me know.

Chris

 

[MacombMonitor]

It certainly sounds like you know what you're doing, and from a programming standpoint it might be a fun project. But does the end justify the means?

i.e.;

What did the transmitter say to the garage door opener?

I don't know.

00101110101001001110110

 

[Thayne]

Maybe you can make it get women to you know, open up certain things on demand

 

[Al42]

It certainly sounds like you know what you're doing, and from a programming standpoint it might be a fun project. But does the end justify the means?

i.e.;

What did the transmitter say to the garage door opener?

Mine doesn't say anything. Must be some sort of SS, because close call didn't pick anything up from zero distance.

 

[TeRayCodA]

What freqs? 300+Mhz?

 

[SCPD]

This gave me the idea of writing a program to decode these little "data bursts", to find out the actual code the opener sends.

Hi Chris;

I could be wrong but I think these circuits use SAW filters instead of actual crystals for the oscillators. The SAW filters are cheaper. The result is that transmitter and receiver can be slightly off in frequency. To cope with this, the transmitter's signal is "wiggled" across a much wider spectrum than normally necessary - just enough to guarantee overlap with the receiver's tuned frequency. For someone using a receiver with a relatively stable crystal controlled reference (like your scanner) the resulting signal is very hard to recognize - you might have to experiment with wider passband that normally found in most consumer receivers.

-rick

 

[hotdjdave]

Most older and cheaper newer garage door openers are in the 300 MHz range. Switching the dip switches changes some type of tone, similar to some sort of hybrid of CTCSS and DTMF (so I have heard).

I used to live in a townhouse complex. They gave me a garage door opener that opened the gates and my garage. One day, for some unknown reason, I discovered that my opener starting opening several gargage doors at once when I pressed the button to open the gate, and other garages when I opened my garage. This went of for a week or so. One day when I came up to the gate, the complex manager was standing there checking everyones openers. When he checked mine, the jig was up - I played stupid :roll: . He took me to his garage, opened up the opener, pulled out the circuit board and smashed it with a hammer and gave me a new circuit board, after reprogramming it to my garage. This was better anyway, I was getting tired of worring about other peoples garages being open.

I always wish I was able to figure out how my garage door was able to open several doors at once.

 

[xoclipse]

Hi Chris;

I could be wrong but I think these circuits use SAW filters instead of actual crystals for the oscillators. The SAW filters are cheaper. The result is that transmitter and receiver can be slightly off in frequency. To cope with this, the transmitter's signal is "wiggled" across a much wider spectrum than normally necessary - just enough to guarantee overlap with the receiver's tuned frequency. For someone using a receiver with a relatively stable crystal controlled reference (like your scanner) the resulting signal is very hard to recognize - you might have to experiment with wider passband that normally found in most consumer receivers.

-rick

Yeah that could be a possibility, but I'm pretty sure it is pretty stable on 390mhz. I checked the FCC's fccid lookup site, https://gullfoss2.fcc.gov/prod/oet/cf/eas/reports/GenericSearch.cfm, and put the FCCID of the transmitter, which is B8QGT25, and it came up on the site as having an upper frequency of 390.0mhz, and a lower frequency of 390.0mhz. So I assume that means that it doesn't vary too much, but i'm obviously not 100% sure. I think most garage door openers in the US operate between 300mhz and 400mhz, so if you don't have the FCCID you could probably use a limited search on a scanner to pick up the frequency.

Right now I'm working on trying to find the datasheet for the component inside my garage door transmitter. It's made my Micrel, with a part number of Y22758C. Hopefully if I can find some more information on this it will help me in understanding how it exactly transmits.

 

[Joseph11]

EDIT: Nevermind, read post wrong.

 

[HillbillyUHF]

EDIT: Nevermind, read post wrong.

---GUMP---

 

[Mozilla]

Garage door reader

Its been done several times, by both individuals and companies. There use to be a kit available and also a local company here makes them for government and official use, but it is an interesting project.