Step 4: Figure Out What's Going on Inside

The remote is powered by a 9V battery. My logic analyzer is only rated for 5 volts, so I want to check out what's going on with the DATA line before hooking it up to my logic analyzer.

If the signal on the DATA line is 9 volts, I have to do some tricks to get it down to 5V for the logic analyzer.

I connected an oscilloscope probe to the DATA line, and GND to the GND line on the remote. I set the trigger to two-ish volts and pushed a button. Out comes data! Sweet. This looks very hackable!

Turns out, the data line is only 3 volts. The distance between the horizontal dotted lines on the oscilloscope display is 2 volts.

The RF module looks like a pretty simple device, so I'll just assume that it can handle 5 volts as well as 3. The micro controller will be running at 5 volts.
<p>Really good instructable. But I did not use such expensive tools for analysing.<br>I used open logic sniffer program with an Buspirate and 433MHz receiver Module.<br>But I have now built stef mientkis spectrum analyzer and used it that way. http://mientki.ruhosting.nl/data_www/raspberry/doc/si4432_ook_detection.html</p>
<p>Very good instructable. <br>It worked on Klik aan Klik uit remote switches. Instead of buying an expensive logic analyzer I used an Bus Pirate I already had.</p>
<p>Though usually I get reasonable results with an Tf sniffer, there are those remotes that though I know they work on 433 Mhz just are not picked up by the sniffer.<br>Logic probe is indeed very handy in those cases</p>
<p>wow, checksum calculation. my head just exploded. </p>
just few minute back, I post a thread http://www.edaboard.com/thread305974.html#post1309531 <br>, but now I found very useful page(this).. <br>I have not read whole article but ,, it seems very useful for me.. <br>thanks to author of this post.. chr <br>
G8 Work........
G8 Work
Bought a 5-pack of these things (US 120V version) and will hopefully have them next week! I really hope they have the separate radio chip like yours, this is such a clean way to do it (opposed to the soldering wires on button pads). If it has a standard 433MHz transmitter I might buy one just so I can keep the remote and still have PC/network/phone control. <br> <br>Ultimate goal is a home automation system driven off a RasPi, with web interface, timers, sensors, etc.
Link so i can buy some too please
They didn't work out too well, ended up buying some from Walmart (Holiday Time brand, seasonal only) that were 3 to a pack (bought 2 packs). The 5-pack only had toggle buttons, they didn't have different commands for on and off. I did the same method of reverse engineering the protocol and used an ATTiny to reproduce the signals. I did my own Instructable about it as well.
Hi! <br>Like your tutorial very much. <br> <br>It inspired me to put togather an instructable too. <br>https://www.instructables.com/id/Wireless-power-outlets-for-home-automation-using-A/ <br> <br> <br>Can one use voltage doubler for RF transmitter using 2 capacitors and 2 diodes. <br>http://www.reuk.co.uk/Making-Voltage-Doublers-and-Multipliers.htm <br>Sorry, I put your picture about voltage booster in the description. Is it OK or should I remove it. <br>
very good, its great ! <br>fred
i love how thorough your explanations are !<br>well done <br>you made me interested in taking my circuits course again ha ha
cool thanks
i have absolutely no experience with building things like this but im starting my studies in electrical engineering soon and i want to build something cool like this very badly. any thoughts or suggestions?
This deserves to win the contest =)
I was an EE student and this instructable was fantastic. It was an excellent walkthrough that teaches you the theory of digital circuits through a custom/cool and practical implementation. Awesome Logic analyzer btw, gonna pick up one of those for myself perhaps to replace the one i hate. Incredibly well done and really invaluable. This is like a digital control programming class and a lab in ONE instructable. Just amazing.<br><br>Nice Oscilloscope btw, looks like an expensive one. Sparkfun has a really nice usb oscilloscope just like the logic analyzer you used/referenced. Both of them are at the bottom of their tools page. http://www.sparkfun.com/categories/177. I'd love to see this done with some of the xbee units they sell, but doing it this way might be cheaper.
Thanks for the excellent explanaition and idea!!!!<br>its nice that you explain the logic and order.<br>keep it up!
This is an awesome inscrutable. It has helped me a great deal with digital circuits. Thanks again.
Some projects are, I'm sure, quite inscrutable--this doesn't sound too bad. ;-)
This is exactly why this site and DIY is AWSOME!
Hello Everyone!<br><br>Realy nice prodjekt :-)<br><br>There is a product from a swedish company www.telldus.se named tellstick. <br>I have run this i 4 years with linux and windows and itś very easy to set up and work like a charm<br>there is also many 3part application.<br><br>/Andreas
This is simply AMAZING!<br>This is what i was looking for! V-USB + RF+Android !<br>How can i say.....you're the best (:<br>Best instructable I've ever read!
Very very nice. Cool beginners guide to reverse engineering. Thanks for that!
Isn't the zener diode reverse connected in the schematic?<br>We want the diode to reverse bias, not to forward bias.
Very Well Done!!!! -Lee
This is pretty cool. For my A-Level electronics project I reverse engineered an RGB LED remote that I got cheap of eBay, found the protocol much like you, and used it to control my own coloured lights which decoded the protocol! Cool
Don't turn it on, take it apart!..<br><br>I assume you are also suffering from an eevblog overdose? :)<br><br>nice writeup, cheers!
I've published a similar project some weeks ago (but more protocols and pcb available):<br>http://www.maltepoeggel.de/?site=usbfunk
Nice work!
That's COOL!<br>I understand you can control the mcu by PC through USB, but how do you control the PC by cell phone?!?! By blue tooth?! wifi? How?!!?
Another option is to purchase the encoder ICs that most of these remote systems are based on. I picked up several encoders and decoders on ebay for a similar project. Had to order from China, though. <br> <br>They are usually PT2262 (encoder) and PT2272(decoder) <br> <br>I think this is awesome that you decoded the protocol, however. Lower parts count, yeah!
Excellent! I have fairly rudimentary electronics knowledge, so this was practically a tutorial on using a logic analyzer and reverse engineering communication protocols. Not just a quick how-to, but something that I can take as a beginning step for doing similar stuff. Thanks!
Nice: here is something similar that i did<br>http://linux-utils.blogspot.com/2011/01/arduino-remote-control-outlet.html<br>the kit was cheap (15&euro;, 2 RF outlets modules and the remote control)
to do the thing with an rfm12 module, take a look at ethersex. there even is another libra set on the compatibility list, so i think it should work out of the box.<br>http://ethersex.de/index.php/RFM12_ASK
coool...<br>can we have the pcb layout??
There is no pcb layout, it is soldered on a protoboard..
Only now I see that you published .sch too... sorry.<br>very funny project.<br>I've made it in the lame way (16f627 + transistors), but it should be fine to control a lot of other receiver.<br>tnx a lot
Very impressive!
This is so BOSS! its awesome!

About This Instructable




Bio: I like microcontrollers and LEDs :D
More by chr:Reverse Engineering: RGB LED Bulb with IR remote Reverse engineering: USB controlled home automation hack LED Cube 8x8x8 
Add instructable to: