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Thread: MQB Instrument Cluster Lighting - Help needed

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    MQB Instrument Cluster Lighting - Help needed

    Hi, all
    Not sure if there is anyone here who can help, but I'm interested in understanding how MQB vehicles manage the dimming behaviour of the instrument cluster - from a software perspective. I've been trying for some time to explore this aspect of my own mk7 and it's proving to be somewhat of a problem

    Here's what I have managed to glean from my efforts so far (still many knowledge gaps-alas):

    Regardless of what model mk7 I look-at (my own car, or others) and irrespective of the country in which the car is sold, VW appears to use the same matrix structure for controlling the illumination of the instrument cluster. I haven't checked other MQB vehicles (like Audi A3?), but I suspect that they will have the same arrangement.

    In 17-Instrument control module, there are five different aspects of the cluster that can be controlled. These functions are:

    1. Clock Dial -Day
    2. Clock Dial -Night
    3. Gauge
    4. Indicator Lights
    5. Middle Display - Main Field

    The control module devotes 12 x adaptation channels for each of these functions (i.e. a total of 60 x channels in all) arranged as follows:
    1. The channel descriptors always start with a number in parentheses (i.e. 1 to 12) followed by "dimming_characteristic_curve_adjustment"
    2. 6 x adaptation channels are devoted to "X" values (i.e. X1,X2, X3...X6) and a further 6 x adaptation channels are assigned to "Y" values (i.e. Y1, Y2, Y3, .. Y6).
    3. The settings in the "X" value channels are hexadecimal and they appear to range from Hex00 to HexFD (i.e. a total of 253 possible values)
    4. The settings in the "Y" value channels are also hexadecimal and they appear to range from Hex00 to Hex64 (i.e. a total of 100 possible values)

    In addition to the above, the instrument control module has a further 10 x adaptation channels that it allocates to something called "internal_phototransistor". Clearly, these are the software values for the physical device that modulates the illumination of the cluster according to the prevailing light levels in the cabin. Anyhow, this further set has exactly the same structure as the five functions above except that there are only 5 x "X" channels and 5 x "Y" channels . Also, the range of hexadecimal values for internal phototransistor is much larger (see table below).

    Here's a table that summarises the settings for these "dimming_characteristic_curve_adjustment" entries for all 70 Adaptation channels (the values in the table are universally the same for all mk7 models that I have looked-at):



    The only (simple) observation that I can make from the table is that the values appear to monotonically increase with increasing X/Y numbers . I'm guessing that one of the ranges is an illumination value and perhaps the other is some type of dimming value- but this is pure speculation on my part.

    Does anyone here have any insights as to how these adaptation channels operate and more importantly, how they can be used to alter the instrument cluster illumination (for tweak purposes)?

    Thanks in advance

    PS: Here's the actual adaptation channels and their settings for the "dimming_characteristic_curve_adjustment" entries from my 103TSI.

    Code:
    103TSI	
    17- Instrument  control module 	
    Adaptation Channel Description	Setting
    (1)-dimming_characteristic_curve_adjustment_clock_dial_day-X1	0
    (2)-dimming_characteristic_curve_adjustment_clock_dial_day-Y1	0
    (3)-dimming_characteristic_curve_adjustment_clock_dial_day-X2	32
    (4)-dimming_characteristic_curve_adjustment_clock_dial_day-Y2	0
    (5)-dimming_characteristic_curve_adjustment_clock_dial_day-X3	66
    (6)-dimming_characteristic_curve_adjustment_clock_dial_day-Y3	0
    (7)-dimming_characteristic_curve_adjustment_clock_dial_day-X4	96
    (8)-dimming_characteristic_curve_adjustment_clock_dial_day-Y4	5
    (9)-dimming_characteristic_curve_adjustment_clock_dial_day-X5	DC  
    (10)-dimming_characteristic_curve_adjustment_clock_dial_day-Y5	14
    (11)-dimming_characteristic_curve_adjustment_clock_dial_day-X6	FD  
    (12)-dimming_characteristic_curve_adjustment_clock_dial_day-Y6	64
    (1)-dimming_characteristic_curve_adjustment_clock_dial_night-X1	0
    (2)-dimming_characteristic_curve_adjustment_clock_dial_night-Y1	2
    (3)-dimming_characteristic_curve_adjustment_clock_dial_night-X2	0A  
    (4)-dimming_characteristic_curve_adjustment_clock_dial_night-Y2	2
    (5)-dimming_characteristic_curve_adjustment_clock_dial_night-X3	32
    (6)-dimming_characteristic_curve_adjustment_clock_dial_night-Y3	0E  
    (7)-dimming_characteristic_curve_adjustment_clock_dial_night-X4	64
    (8)-dimming_characteristic_curve_adjustment_clock_dial_night-Y4	1E  
    (9)-dimming_characteristic_curve_adjustment_clock_dial_night-X5	96
    (10)-dimming_characteristic_curve_adjustment_clock_dial_night-Y5	32
    (11)-dimming_characteristic_curve_adjustment_clock_dial_night-X6	FD  
    (12)-dimming_characteristic_curve_adjustment_clock_dial_night-Y6	64
    (1)-dimming_characteristic_curve_adjustment_gauge-X1	0
    (2)-dimming_characteristic_curve_adjustment_gauge-Y1	9
    (3)-dimming_characteristic_curve_adjustment_gauge-X2	0A  
    (4)-dimming_characteristic_curve_adjustment_gauge-Y2	9
    (5)-dimming_characteristic_curve_adjustment_gauge-X3	32
    (6)-dimming_characteristic_curve_adjustment_gauge-Y3	19
    (7)-dimming_characteristic_curve_adjustment_gauge-X4	64
    (8)-dimming_characteristic_curve_adjustment_gauge-Y4	30
    (9)-dimming_characteristic_curve_adjustment_gauge-X5	DC  
    (10)-dimming_characteristic_curve_adjustment_gauge-Y5	5A  
    (11)-dimming_characteristic_curve_adjustment_gauge-X6	FD  
    (12)-dimming_characteristic_curve_adjustment_gauge-Y6	64
    (1)-dimming_characteristic_curve_adjustment_indicator_lights-X1	0
    (2)-dimming_characteristic_curve_adjustment_indicator_lights-Y1	5
    (3)-dimming_characteristic_curve_adjustment_indicator_lights-X2	0A  
    (4)-dimming_characteristic_curve_adjustment_indicator_lights-Y2	5
    (5)-dimming_characteristic_curve_adjustment_indicator_lights-X3	32
    (6)-dimming_characteristic_curve_adjustment_indicator_lights-Y3	0C  
    (7)-dimming_characteristic_curve_adjustment_indicator_lights-X4	64
    (8)-dimming_characteristic_curve_adjustment_indicator_lights-Y4	17
    (9)-dimming_characteristic_curve_adjustment_indicator_lights-X5	96
    (10)-dimming_characteristic_curve_adjustment_indicator_lights-Y5	32
    (11)-dimming_characteristic_curve_adjustment_indicator_lights-X6	FD  
    (12)-dimming_characteristic_curve_adjustment_indicator_lights-Y6	64
    (1)-dimming_characteristic_curve_adjustment_middle_display_main_field-X1	0
    (2)-dimming_characteristic_curve_adjustment_middle_display_main_field-Y1	1
    (3)-dimming_characteristic_curve_adjustment_middle_display_main_field-X2	0A  
    (4)-dimming_characteristic_curve_adjustment_middle_display_main_field-Y2	1
    (5)-dimming_characteristic_curve_adjustment_middle_display_main_field-X3	32
    (6)-dimming_characteristic_curve_adjustment_middle_display_main_field-Y3	7
    (7)-dimming_characteristic_curve_adjustment_middle_display_main_field-X4	64
    (8)-dimming_characteristic_curve_adjustment_middle_display_main_field-Y4	0E  
    (9)-dimming_characteristic_curve_adjustment_middle_display_main_field-X5	96
    (10)-dimming_characteristic_curve_adjustment_middle_display_main_field-Y5	1E  
    (11)-dimming_characteristic_curve_adjustment_middle_display_main_field-X6	FD  
    (12)-dimming_characteristic_curve_adjustment_middle_display_main_field-Y6	64
    (1)-dimming_characteristic_curve_adjustment_internal_phototransistor-X1	00 00  
    (2)-dimming_characteristic_curve_adjustment_internal_phototransistor-Y1	00 00  
    (3)-dimming_characteristic_curve_adjustment_internal_phototransistor-X2	00 32  
    (4)-dimming_characteristic_curve_adjustment_internal_phototransistor-Y2	00 0E  
    (5)-dimming_characteristic_curve_adjustment_internal_phototransistor-X3	00 64  
    (6)-dimming_characteristic_curve_adjustment_internal_phototransistor-Y3	00 41  
    (7)-dimming_characteristic_curve_adjustment_internal_phototransistor-X4	00 C8  
    (8)-dimming_characteristic_curve_adjustment_internal_phototransistor-Y4	00 C8  
    (9)-dimming_characteristic_curve_adjustment_internal_phototransistor-X5	01 F4  
    (10)-dimming_characteristic_curve_adjustment_internal_phototransistor-Y5	00 FD
    Last edited by DV52; 04-08-2015 at 10:54 PM.
    VW Golf MkVII (MY13) - A3 8V hatch (MY17)

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    Don:

    I am not sufficiently well educated in electronics to make a scholarly response to your question, but I can offer a thought based on my past experience with aircraft instrument panel lighting design.

    I was responsible for all aspects of flight compartment design for a medium sized transport aircraft developed during the time period 2008 - 2011. I specified that about 14 different lighting circuits (analogous to the 5 aspects of the instrument cluster you identified) all be controlled by one dimmer dial, and in addition to that, that a photocell be provided that would automatically dim or brighten LCD panel backlighting (screen backlighting, similar to the screen between the Golf speedometer and tachometer) in response to changes in ambient light level. My objective here was to avoid the need for the pilot to adjust the single dimmer control if the aircraft went in and out of cloud, or if it turned in such a way that the sun started shining in through the side windows onto the displays.

    An Electronics Engineer implemented this design specification for me, and I recall that he had to create 'dimming curves' for the various circuits. I didn't study those in depth (they were way over my head), but during flight test, the EE and I both realized that we needed different behaviors (different speeds) for lighting increase vs. lighting decrease. Attack (increase in light levels) needed to take place significantly faster than decay (decrease in light levels). Hence, the EE needed to develop one set of dimming curves - which were expressed as numerical matrices, much like the VW table you posted - for light increase in response to what the photocell sensed, and a different set of dimming curves for light decrease sensed by the photocell. On top of that, various components (LCD display screen backlighting vs. bezel backlighting vs. annunciater indicating intensity) needed different dimming curves to create a consistent look across the whole instrument panel, this due to different characteristics of the illumination within the component.

    So, based on that experience, I speculate that VW may have created one set of curves for increased illumination, and a different set of curves for decreased illumination. It is also possible that somewhere in there a certain amount of hysteresis has been specified so that the brightness level does not change rapidly when driving beneath a small bridge, or past a tree that is casting a shadow on the road.

    Hope those thoughts help you figure it all out.

    Michael

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    Michael: good to hear from you and many thanks for your reply. I'm constantly blown-away by the intellectual KWs (or, "horsepower" for those that don't use SI units) in the responses that I read on this forum. It's a bit scary and somewhat intimidating- but it's a good thing for us "learners"!!

    Anyhow, I do like your hypothesis - not only because it makes sense, but also because it's anchored in a bedrock of practical experience. Your theory regarding the relative importance of the "attack" (what a great use of the term - and a very male use of the term!) characteristics is kind-of consistent with the fact that the "X" values have a much finer granularity than the "Y" values.

    So, using the newly established PP (Paneuropean Principle) and extrapolating your hypothesis, perhaps each of the 5 x X/Y settings for the internal phototransistor aligns with a matching X/Y setting for each of the five functions in my table? And the sixth X/Y setting in the five functions is for the off-position ( I'm guessing "X6" & "Y6").Serendipitously (and it was sheer luck) my table is arranged this way. But I had no inkling of this (possible) relationship when I created the table - kismet perhaps?

    Hmm..... whilst I'm a firm believer in Occam's razor, this sounds way too simple for anything that VW's engineers have designed!

    Your suggestion is a good starting point (thanks again). All I need to do now is to put "some flesh on the bones"- perhaps a bit of experimentation is needed, me thinks

    Any additional insights that shed further light on the matter (pun intended) would be welcomed!
    Don
    Last edited by DV52; 04-09-2015 at 07:41 PM.
    VW Golf MkVII (MY13) - A3 8V hatch (MY17)

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    Michael: just a short post by way of an update regarding your valuable advice above (thanks again). My amateur sleuthing thus far confirms what you have said in your post. It appears that the "X" values refer to brightening cabin conditions and the "Y" values relate to darkening cabin conditions with X5 and Y1 being the "extreme set points". X6 and Y6 do indeed represent the illumination levels when the rotary switch is in the off position. All good new knowledge - made possible by your catalyst advice!!

    Even managed to create a new set of "dimming adjustment curves" for my golf so that the instrument cluster now illuminates when the rotary light switch is in the off position (different illumination levels for daylight and nigh-time conditions)

    Woowee- next project is splitting the atom!!
    VW Golf MkVII (MY13) - A3 8V hatch (MY17)

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    Hi Don:

    Great to hear that you are making progress. You are working at a post-doctoral level, compared to me poking around at a kindergarten level.

    FYI, I'm going over to Europe on Wednesday, and will be there (riding around on my moto) for about 6 weeks. I'm going to spend a bit of time poking around VW dealerships in Germany, this because there are a few things that I want to investigate for possible retrofits to my Golf: Park Distance Control (the small sensors on the bumper, these are not available in Canada), Driver Seat Memory (not sure if this is available anywhere in the world on the MK 7 Golf), and electrically powered folding mirrors (not offered in North America). So, if you would like me to investigate anything for you while I am in Germany, let me know.

    I have today put a letter in the mail to you containing one of the 'snake' coat-holders that fit onto the front seat headrests.

    Regards,

    Michael

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    Quote Originally Posted by PanEuropean View Post
    Hi Don:

    Great to hear that you are making progress. You are working at a post-doctoral level, compared to me poking around at a kindergarten level.

    FYI, I'm going over to Europe on Wednesday, and will be there (riding around on my moto) for about 6 weeks. I'm going to spend a bit of time poking around VW dealerships in Germany, this because there are a few things that I want to investigate for possible retrofits to my Golf: Park Distance Control (the small sensors on the bumper, these are not available in Canada), Driver Seat Memory (not sure if this is available anywhere in the world on the MK 7 Golf), and electrically powered folding mirrors (not offered in North America). So, if you would like me to investigate anything for you while I am in Germany, let me know.

    I have today put a letter in the mail to you containing one of the 'snake' coat-holders that fit onto the front seat headrests.

    Regards,

    Michael
    Michael: What an incredibly generous person you are - thank you!! I'm really grateful that you took the trouble to send the snake thingy - never seen one before.
    Many thanks also for the kind offer at the dealerships. If you can get your hands on any written material about Leuchte channels, or dimming characteristic curves, I would appreciate it. But I suspect that it's all proprietary information for VW employees only. Pity, because it really is a fascinating area to understand!

    Have a great time in Europe
    Cheers
    Don.

    PS: if there is anything that I can send up in reciprocity, please ask - perhaps a giant jar of vegemite (it's very much an acquired taste)!!
    VW Golf MkVII (MY13) - A3 8V hatch (MY17)

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    Sorry, can't resist:

    The engineering problems are likely insurmountable. It would be like proposing to land a rocket booster section on a barge floating in the middle of the ocean.

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    Uwe: arhhhh....... men at work -they truely were our major cultural export in the 70s!
    VW Golf MkVII (MY13) - A3 8V hatch (MY17)

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    They increased Vegemite Awareness by several orders of magnitude in the USA.

    -Uwe-
    The engineering problems are likely insurmountable. It would be like proposing to land a rocket booster section on a barge floating in the middle of the ocean.

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    Ah, this appears to be what I"m looking for, but it will take a while to understand. I'm trying to make it possible to turn the dashboard lights all the way off, or nearly so, using the dimmer switch. I posted my earlier attempts (search for it under my user name 'jgordon'), but had to abandon the effort for a while, just getting back to it now. Have you developed this concept any further?

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