Siren unit control head - Page 1
Forum section: electronics / beginners

author: catbus
author_rank: Newbie
timestamp: December 23, 2012, 09:20:42 pm
content: Hello,I'm not specially good in english, so i'm going to make this short.I have a "control head" to the Fedsig VAMA AS 420 siren, and i would like to learn more about how the controller "talks" to the amplifier unit.My main goal is to interface this controller head with an relay board.What have i found out so far, is that the controller works "independently" and has an PIC16C54 microcontroller. Also, out of 8 wires two are for controller head "operating voltage". So what signals do the remaining 6 wires give out?Here is a picture of the control head unitIs this the transmit pin? This is the signal output from one of the 8 pins from the RJ45 plug (the other end of the control head, that plugs into the siren unit)And here is another shot with almost all of the functions set "on"And a couple PCB shots.Thank you in advance!

author: catbus
author_rank: Newbie
timestamp: December 29, 2012, 08:35:24 pm
content: Anyone care to help?

author: amyk
author_rank: Super Contributor
timestamp: December 30, 2012, 06:11:04 am
content: What do you want to do, figure out the protocol? You'll have to reverse-engineer the schematic and get a better capture of the communication. It looks like a serial one but hard to see from your scope traces.If I remember correctly PIC16C54 code protection was flawed and could easily be broken so you maybe can read the memory.

author: catbus
author_rank: Newbie
timestamp: January 05, 2013, 03:10:20 pm
content: What settings should I set to oscilloscope, to see the traces better?

author: catbus
author_rank: Newbie
timestamp: January 07, 2013, 03:25:37 am
content: Some screenshots viewed on an oscilloscopePin 1Pin 2Pin 3Pin 4 (GND of the operating voltage 12v)Pin 5 (Plus of the operating voltage 12v)Pin 6Pin 7Pin 8

author: amyk
author_rank: Super Contributor
timestamp: January 07, 2013, 10:58:50 am
content: Looks like a synchronous serial protocol, could be SPI or I2C or something custom.7 is clock, 8 is data. I think I can count 16 bits of data, and there's some floaty capacitor-y weirdness going on at the bottom of the signal s.Your scope appears to have 2 channels, you can use both of them together to attempt decoding the data.

author: catbus
author_rank: Newbie
timestamp: January 07, 2013, 03:32:55 pm
content: Thank you very much for sharing your knowledge!The scope is dual channel yes, but I have only one probe at my disposal ATM.Can you recommend a some kind of a "setup" to better capture and read the data?

author: amyk
author_rank: Super Contributor
timestamp: January 08, 2013, 11:55:49 am
content: A logic analyser.

author: catbus
author_rank: Newbie
timestamp: January 08, 2013, 03:49:04 pm
content: I do not have access to a logic analyzer. Only a scope.

author: ve7xen
author_rank: Super Contributor
timestamp: January 08, 2013, 05:50:16 pm
content: Just sticking a random wire into the BNC terminal on channel 2 should get you a usable signal as long as your probe (on the other channel) is supplying ground. Loading will be increased but probably won't pose a problem for serial digital signals.