SHIBBY's blog

If you ever wondered what's inside a GP430LB or how wide is this antenna's bandwidth, you've come to the right place.

If you know a little bit about electronics, you probably already seen TVS diodes. If not, these are Transient Voltage Suppressor diodes, placed in parallel as close as possible to the power supply input of the device, which basically sacrifice themselves by going short circuit when the applied voltage exceeds their rated breakdown voltage. Their response time is fast enough to protect the remaining electronics from damage. That's the good part of the story.
Unfortunately, some electronic board designers don't seem to care about what happens just after that...

N'étant pas certain que cet appareil ait été vendu ailleurs qu'en France, du moins sous la même marque & référence, je vais vous épargner un billet en anglais approximatif :)

Ce système de vidéosurveillance acheté relativement cher il y a quelques années chez Castorama a quelques points faibles, notamment l'accès à distance par une interface web utilisant des ActiveX douteux nécessitant la levée de nombreuses sécurités sur Internet Explorer. De plus, il est obligatoire d'utiliser Internet Explorer 6, qui n'est plus installable sur des ordinateurs récents, ce qui nécessite l'installation d'une machine virtuelle sous Windows XP. Bien entendu, il ne faut pas compter sur un éventuel accès via votre smartphone. De toutes façons, ce n'était pas encore très répandu à l'époque à laquelle ce produit était commercialisé. Ce problème ne sera absolument pas traité dans ce billet, puisque les sources de l'applicatif embarqué ne sont évidemment pas disponibles. Un autre "défaut" de cet appareil pour les particuliers, c'est le fonctionnement constant du rétro éclairage de l'écran: cela consomme de l'énergie, ça émet de la lumière inutilement, et ça réduit considérablement le temps de vie du circuit d'alimentation du rétro éclairage, comparé au temps passé à surveiller ce qui est affiché. Pour une utilisation professionnelle, dans un poste de sécurité par exemple, cela ne pose pas de problème. La modification proposée consiste à dévier le signal de commande du rétro éclairage, afin de permettre une mise en veille manuelle à l'aide d'une interrupteur.

Christmas is not too far away from now and Santa Claus already brought me a gift: a nice faulty electronic toy :) When people usually take back the faulty device to the mall, I prefer to repair it myself as long as it's possible (and also because I bought it from Amazon and I didn't want to send it back since I could not find it elsewhere). This toy called "Jojo pot de colle" (I only know its French name) was supposed to follow the kid, guided by a carrot shaped infrared remote control that the kid attaches to his wrist. Actually, it wasn't able to do anything else than running round and round. So, my first guess was a battery issue: wrong! A motor issue: wrong too! So after opening it and re-soldering a broken wire with no luck, I've played with the oscilloscope around the IR receivers that the toy uses to move towards the kid. One of these receivers seemed to be faulty (no IR reception), but it was actually a PCB issue. These components pins are bent so much that one of them pushed the pad away from the single side PCB and broke the connection to the ground. One more soldering later, the toy was working like it should have since the beginning.

http://dl.shibby.fr/blog.shibby.fr/Toy_repair/JojoPotDeColleRemoteControlProtocol.pdf

Well, I think the protocol description I've made is pretty much complete, now it's time to try every other command than the ones sent by the RC-10 and see what happens (by "see what happens" I mean "pray that the transceiver won't blow up"). I'll write a simple program on a Renesas microcontroller that will convert UART frames sent from my computer with Docklight into a synchronous "SPI like" data frame to the TM-241.
I'll try to update this entry ASAP with some test results.






10/07/2012: Well, after trying to use the R8C/25's integrated USART peripheral for days and a strong headache, I've finally capitulated and written a software protocol based on the Timer RA in "Pulse Width Measurement" mode. It uses the clock signal generated by the transceiver to send and receive data. That's the good news.
The bad news is that the transceiver doesn't seem to accept any command above 0x3F, so after all this hard work I still don't know how the RC-20 sends its commands, which is a little bit frustrating.
I did not waste my time anyway since I've found the purpose of some other bits from the LCD indicators bit field, but I would have liked to find more about the RC-20... I've updated the protocol specifications with my latest finds. I'm interested by any information about the operation of the RC-20 (yes, this is an SOS).

Well, I have nothing much to say, excepted that it seems to work, which is a pretty good thing for what I intend to do with it. However, its LCD displays disjointed stuff, like 40.00 all the time, or 40.40, or 40.80 ... don't know why. I can only see the frequencies stored in the transceiver's memories and call channel, but not the VFO. The VFO data sent by the transceiver seems to be followed by some other data that are mistakenly interpreted as the frequency, so every frequency I set is displayed on the RC-10 then automatically erased with the 40."something". This "something" seems to be a bit field that indicates the power level (LOW, MID & HIGH). Anyways, it shouldn't stop me from hacking it!
Now I have to open the MIC plug and connect the logic analyzer.
To be continued...