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TD5 Speedo Mileage run up circuit


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Sorry, should actually have been:

CFBC CFBC CFBC CFBC CFBD CFBD CFBD CFBD

M'theory goes like this:

Memory space starts off as 8 words of FFFF, thus:

FFFF FFFF FFFF FFFF FFFF FFFF FFFF FFFF

This, I assumed to represent 1.0 miles, from your photo.

Each 2 miles that elapse result in a decrement (big endian) of successive words, module 8, starting at address 0, i.e.

FFFE FFFF FFFF FFFF FFFF FFFF FFFF FFFF represents another 2 miles, i.e. 3, assuming it starts at 1 after clearing it out.

the next mile goes in the next word:

FFFE FFFE FFFF FFFF FFFF FFFF FFFF FFFF = 5

FFFE FFFE FFFF FFFF FFFF FFFF FFFF FFFF = 7

FFFE FFFE FFFE FFFF FFFF FFFF FFFF FFFF = 9

FFFE FFFE FFFE FFFE FFFF FFFF FFFF FFFF = 11

FFFE FFFE FFFE FFFE FFFE FFFF FFFF FFFF = 13

and so on...

So:

to get 197,672 miles :-

197672 divided by 16 gives 12354.5 (ignore the decimal for now)

subtract 12354 from 65535 (i.e. FFFF)

gives 53181. Convert to Hex: CFBD

12354 * 16 gives 197664

so now to add 2 mile increments till we get to the desired mileage, in this case 3 lots,

so decrement CFBD by on in the first four spaces:

CFBC CFBC CFBC CFBC CFBD CFBD CFBD CFBD

And there you have it.

So removal of 12V power from the speedo will loose up to 1.9 miles, which is stored in RAM rather than in EEPROM.

I'd love to know what all the other numbers mean though. There must be a bit for miles/km presumably, and probably a separate 'sensor pulses to distance' calibration perhaps.

What else can a TD5 Speedo do?

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My guess would be that pulses per distance and mph/kph are the same thing, i.e it's just pulse per unit or maybe degree..... time to find that now :)

And top marks for the explanation :D Less than 24 hours since we started the project and already we understand the total mileage storage :)

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I'm thinking Serial number for the speedo and VIN number maybe for the vehicle it was originally on maybe.

It may be a general purpose bit of software the instrument maker uses for multiple vehicles, so CAN bus IDs and things may be in there too.

Can't think of much else though. James, do you know the VIN of the vehicle that the speedo came from?

Kevin

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These are all the numbers I can find printed on it... oh and a gratuitous mileage shot for James :)

The date code on the stepper motor seems to agree with the '03 claim for the vehicle...

In image 4 the number written in the same direction as VDO is 0249, you can only see the 49 in the picture.

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post-25689-0-38250000-1308748885_thumb.jpg

post-25689-0-53287000-1308748904_thumb.jpg

post-25689-0-94011000-1308748927_thumb.jpg

post-25689-0-48164700-1308748944_thumb.jpg

post-25689-0-62838700-1308748961_thumb.jpg

post-25689-0-91984500-1308748982_thumb.jpg

Edited by CwazyWabbit
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I'd guess that there would be a SALLDxy8nmA, where x=ABCHKRSV, y=ABFHM, n is a number, m is a number probably 3

I cannot see any patterns yet.

Freelanders dashs store engine type, odometer and VIN accorning to RAVE.

Love a challenge.

Rob

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, the fractions of a mile aren't stored and neither is the trip mileage from what I can see.

That makes sense. The trip resets on mine if I disconnect the battery.

If you can find the info on the main CPU it can probably play tetris with a bit of frigging :P

Some traffic jam entertainment would be welcome :)

This is superb, so much progress in such a short time. Well done guys.

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I'd seriously doubt the VDO unit is storing VIN info, it's a universal part they flog to LR and knowing LR's development style they'll have done the bare minimum to make it work.

I also doubt that *all* of the data is useful or used in this application, very rare that you'd be using exactly the right amount of space on a device, so it'll just be the smallest version that had enough space on it.

As someone else said, the data will probably include a calibration number, MPH/KPH setting, probably a couple of other options (EG illumination always on) - who knows, you could twiddle a bit and make it into a rev counter :P

Other things I could imagine being stored, either on the quiet or optionally, are store top speed and total up-time / run time.

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The maximum mileage that can be stored therefore is in the region of 1.04 million miles. Has anyone done that sort of mileage in a TD5 yet? It's possible it might rollover in software at 999999 miles due to a lack of digits :D

I can't make a huge amount of sense from any of those other numbers against the hex dump.

Kev

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I read else where in this forum that the transducer gives 4100 pulses per mile.

4100 is 1004 in hex. Exactly what is in word 08. Word 09 is similar. Maybe one value of pluse per mile for the odo and one for the dial?

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I also doubt that *all* of the data is useful or used in this application, very rare that you'd be using exactly the right amount of space on a device, so it'll just be the smallest version that had enough space on it.

True, but an erased device would be all FF, and there are quite a few bytes that are not FF...

Other things I could imagine being stored, either on the quiet or optionally, are store top speed and total up-time / run time.

Well yes, useful for warranty claim disputes etc. We do know that this particular unit has done at least 120mph, which is pretty fast for a TD5 :lol:

Kev

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I'd seriously doubt the VDO unit is storing VIN info, it's a universal part they flog to LR and knowing LR's development style they'll have done the bare minimum to make it work.

I also doubt that *all* of the data is useful or used in this application, very rare that you'd be using exactly the right amount of space on a device, so it'll just be the smallest version that had enough space on it.

As someone else said, the data will probably include a calibration number, MPH/KPH setting, probably a couple of other options (EG illumination always on) - who knows, you could twiddle a bit and make it into a rev counter :P

Other things I could imagine being stored, either on the quiet or optionally, are store top speed and total up-time / run time.

I'd say there are some mods for Rover though as there is a specific Rover sticker on the PCB.

In this particular case I doubt it's storing the top speed as nothing changed when I ran it from the signal generator at an indicated 120MPH, if it has stored it then James will have some explaining to do to the authorities as to how he managed that speed in his 110 :) Although it is a very good point and recording uptime would be a very strong possibility even if just to sort out warranty issues between VDO and Land Rover.

I might try some 'bit flipping' this evening to see if I can get it to read different speeds while running on a known clock speed.

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If 'tis true that 4100 pulse/mile (0x1004) is stored in word 8, then 2562 pulse/mile gives 0x0A02 - might be useful if a km conversion is required. There was talk of this on another thread only a week ago or so.

Kev

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4100 is 1004 in hex. Exactly what is in word 08. Word 09 is similar. Maybe one value of pluse per mile for the odo and one for the dial?

Good idea, I've tried a few different values in that word now and anything other than 0x1004 have so far left it refusing to move the needle :( all works fine again when it is changed back though

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There are a couple of factors with KPH conversion - the pulse-per-mile number would change if its internal units of measurement were miles, but presumably there is a bit somewhere to tell it whether to display miles or KM on the display, and probably also to tell it what the scale of the face is (0-120, 0-140 etc.) - otherwise setting 2562ppm would mean your needle would indicate a lot faster then you were really going (pointing to 70mph when you're doing 70kph).

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otherwise setting 2562ppm would mean your needle would indicate a lot faster then you were really going (pointing to 70mph when you're doing 70kph).

Of course, you'd replace the background of the dial with one that has the letters 'km/h' rather than 'mph', so it would probably have a suitable km/h scale too. The sensor pulses per stepper motor steps / degree of needle deflection would remain the same.

Sure different speeds e.g. 140mph rather than 120mph would need a different calibration factor for the road speed versus needle angle, as RJF was suggesting.

Google tells me that 1 mph = 1.609344 km/h so the 2562ppm might be slightly out (2547.621 pulses)

Kev

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Of course, you'd replace the background of the dial with one that has the letters 'km/h' rather than 'mph', so it would probably have a suitable km/h scale too. The sensor pulses per stepper motor steps / degree of needle deflection would remain the same.

Sure different speeds e.g. 140mph rather than 120mph would need a different calibration factor for the road speed versus needle angle, as RJF was suggesting.

Google tells me that 1 mph = 1.609344 km/h so the 2562ppm might be slightly out (2547.621 pulses)

Kev

Don't forget the total distance traveled recording, that isn't in pulses per angle of stepper motor, that must be a pulses per unit factor.

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Is that a warning light in the middle of the dial, just above the needle pivot? Can you tell I've never seen a TD5 speedo? :)

If it is, I wonder if it's a speed warning light. I think some markets (Japan?) have overspeed warning lights at 120kmh. Maybe one of the bits toggles this? My first guess would be word 10 (currently 8000, only one bit set)

Rob.

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Is that a warning light in the middle of the dial, just above the needle pivot? Can you tell I've never seen a TD5 speedo? :)

If it is, I wonder if it's a speed warning light. I think some markets (Japan?) have overspeed warning lights at 120kmh. Maybe one of the bits toggles this? My first guess would be word 10 (currently 8000, only one bit set)

Rob.

There looks to be a red light there, but I've never seen one of these in a vehicle :D, I'm just doing this for the challenge and because I think people being charged a £100 for changing a few bytes is a bit rough.

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The LED is for the alarm/immobiliser, it's controlled via the alarm ECU. Ground one of the pins on the speedo and it'll come on I believe :)

120kph overspeed light as used in Gulf states (among others) is on the normal dash warning panel with the other lights, indicators etc.

Edit: It's pin 3 of the upper plug that needs to be grounded for the LED to come on. Pin 6 (one of the permanent supplies) is the supply to the LED it would seem.

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