Decoding & Cloning The Lucas 5AS Immobiliser - PART II ADDED

[rj]

Andrew,

Amazing write-up once again.

I am not sure I'd want to have a socket in the unit in the car. PLCCs are known to "climb out" from the sockets on PC mainboards etc. When I worked with PCs, problems were often solved just pushing back either PLCCs or memory ICs.

[revilla]

Thanks Regin, yes something to bear in mind. They certainly don't feel.like they could come loose but I know what you mean, with vibration walking the IC pins up the contact springs.

I'm.on the lookout for something like what is shown in this picture:

Any ideas?

I'm the meantime I'll keep a close eye on things and if I hit immobiliser issues I'll know where to look first. The good thing is that even though the immobiliser transmits it's code continuously, once the ECU has received it it doesn't care any more. Once the engine is running you can lose the immobiliser and nothing will happen until it next powers down, so if the chip did come loose it couldn't kill my engine at a dangerous moment.

[revilla]

I suppose if all else fails, once I've got everything programmed and set up a spot of suitable adhesive under the chip would make sure it doesn't go walkies.

[rj]

sHmm.

Not sure where to get the "lock spring" but I do remember them from the early 1990s.

I will ask a local computer geek if he has anything with them on.

The other issue is the oxidation of the pins that, in a humid environment, can cause a lot of trouble.

Yes... I have a lot of crap ideas...
 

[revilla]

LOL so glad I bought those sockets now ... I'll probably end up soldering them back in when I'm done!

[rj]

Sorry...

[revilla]

The more I think about that algorithm for generating the flash patterns the more I like it (very geeky I know)! You can generate a wide range of visually distinct patterns with single, double or even quadruple pulses and one second, half second, quarter second etc. periods that are really easily to tell apart. And all you need in the software is one single byte memory location as a counter shared between all the different timing functions and updated on a timer interrupt or something. All of the flash patterns such as the double pulse "low fob battery" warning, the fast flash whilst arming, even the horn and hazards flashing with the alarm are all compatible with that one generator, just using different masks. Very neat way to squeeze a lot of different timing functions into a very small memory footprint when resources in a microcontroller are scarce.