vcds for dummies - ask a stupid question thread

For fun, I thought I would start a thread where anyone can ask those pesky 'stupid' questions that you were too afraid to ask.

To start, something that has been bugging me for a while that I haven't seen a good explanation of.

long coding vs short coding vs adaptations?

I know coding is the stream of bytes and bits that various controllers use to maintain their configurations/preferences/settings/etc.

I do understand that the vehicle electrical system is a network, not unlike an ethernet network, different devices send different packets with all kinds of different information. Other devices can read and/or return responses to other devices messages.

Long coding is obviously the really long string, and short coding are the shorter ones (less than 10 positions?).

I am not sure why or what determines the coding length, other than than I suppose the module itself.

I am not sure how adaptation(s) work, and how they are related to various settings/tweaks/etc, or to the long/short codings.

so if anyone can explain 'the long and the short' of it (pun intended) in simple man terms, that would be awesome!

and don't worry, I have plenty of other stupid questions to ask if no one else steps up to the plate.

OK, I'll try
Coding is some way of "personalizing" electronic control units. To switch on or off several options and capabilities of standard software programmed into module. Mainly it's made to make manufacturers and repair technicians life a bit easier. They could make series of exactly the same modules and "personalize" them depending on equipment of car where module will be installed. Older generation modules have only some options that could be changed. For example old TDI or whatever ECU will have coding 00001 or 00002 depending on transmission (manual or automatic) it has to work with. This is called short coding.
But a decade of years newer Central Electric module have a bunch of options that could be "personalized" - for example headlights - halogen, xenon or bixenon. Fog lights - installed or not. Rear lights - classic ones or LED ones. DRL mode - depending on local law for DRL use in different countries/regions, different combinations of exterior lighting bulbs are switched on in DRL mode. And those are only some options of all capabilities of module. Its clear that 5 decimal symbols are not enough to describe all possible personalization variants of such module. There long coding is used.
Adaption, in couple words, is teaching control module how to use some device, connected to it. Some sensors must be "adapted" - by meaning to teach control unit how to interpret parameter measured by this sensor. For example G450 - differential pressure sensor for DPF. There are two pressure sensors inside this part. One is measuring exhaust gas pressure before DPF, second one after. Pressure difference is sent to ECU by electric signals. To make a new one sensor's measurements more accurately interpreted by ECU, it must be adapted (there i'd better use word calibrated). It's done that way, that in moment engine not running, You know that both pressures are equal. In that moment You "say" to ECU by sending special command to him "hey, this is zero pressure difference, remember that"!

Short coding will be in decimal numbers, long coding will be in hexademical.

Some short codings will match the sequence of hexademcal string...etc 0...1.....2...4..8..16..32..64..128....65666
Some don't and you have to change number of short coding to match needed option 11x11- either 1..2..3.. ..9

On newer golfs the lightning options on BCM go through adaption channel. It's all about how manufactor desires.

As there are 2000+ adaption channels for light configuration in mk.7, i see the point of adding them as adaption and not coding.

All coding and adaptions are contained & than directed to a specific criteria "Flash" table from "EEprom".

This is written in EEprom in HEX and at a specific HEX address......... & sometimes encrypted or byte swapped/inverse or additionally often "a checksum" of a block or both being overall.

Depending on the tester used.......... these inputs can be input in HEX or DEC.
The interface and program how it was written, is what allows based on its ability to confirm the allowed changes in EEprom authorized by the Flash.

Additionally:

Tuners which have "switch tables" are doing nothing new and exploit these map tiers.......it is nothing other than a coding change to a new map they wrote in the flash.

EEprom also contains the adaptations and learned adaptions of Immobilizer CP/MAC data, status, VIN #, such as Last TV, FP last duty cycle, OXS, MAF, DTC pointed flags, readiness status/tests and bits OTP recognition or processor boot point for diagnostic stack or protocol etc. etc..

Coding length, value, and position allowed........are determined in the Flash.

Hi, Jack!
I feel, Your explanation is not for "dummies"

Nice, thanks all very helpful!

Ok, so I understand that you may not want 2000+ bytes/channels in a lighting packet or long coding.

I also understand that adaptations are or can be used to adapt or calibrate sensors to a known state, but I'm not quite grasping how or why adaptations would be used for the example provided 2000+ light channels ?

Hi, Jack!
I feel, Your explanation is not for "dummies"

Click to expand...

Than maybe start the thread as for the really really dumb..........for real!

Dumb is a perspective........... I believe that I am dumb depending on who I am in the room with.

I know my place and respect my elders.........even if they are stupid.

D-Dub said:

Nice, thanks all very helpful!

Ok, so I understand that you may not want 2000+ bytes/channels in a lighting packet or long coding.

I also understand that adaptations are or can be used to adapt or calibrate sensors to a known state, but I'm not quite grasping how or why adaptations would be used for the example provided 2000+ light channels ?

Click to expand...

D-_Dub:

I also had problems understanding the two basic concepts of long coding and adaptation channels when I first got my cable, but I now have a model in my mind that makes sense to me - albeit I have not been able to find any written confirmation of my hypothesis, anywhere.

Many years ago as a young student I was taught that control systems (and the modules that manage them) really only consist of three variables: input, output and feedback!

Coding (long and short) are those variables (often plain, ordinary binary switches) that inform the control modules about inputs -stuff such as what equipment is connected (like anti-theft alarm, fog lights, cruise control etc) and what input variables to use (like light sensor thresholds, radio frequency bands, side-of-road etc)

Adaptation channels on the other hand are the parameters that tell the control module about outputs - specifically how to manipulate output signals (like how to control lighting - what lamp type, what illumination levels etc, how to lock/unlock doors, when the car was serviced etc)

Feedback is the program and firmware that the control module uses to perform the myriad of functions that it manages

As I said, it's a very simple concept that may be entirely incorrect, but it works for me!!

Don

I'm not sure there is a universally correct way to describe this stuff. Much depends on the control module in question.

-Uwe-

Knowing VW, they're probably reporting the wrong values anyway....