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Author Topic: Terminology questions, speedo questions  (Read 3307 times)
wmorri65
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« on: November 13, 2017, 01:04:42 PM »

When I read that a map is 8x1, 16 bit, what exactly does the 8x1 part mean?

I know what 16 bit is. I suspect 8x1 is like a one-dimensional array. Is that right? 8 of what, 16 bit values? So 16 bytes, or 128 bits?

So if some map were, let's say, 8x4, is that a two-dimensional array with 8 columns and 4 rows?

Just trying to understand the terminology being used here.

As far as speedometer questions, I'm trying to find and understand the map that controls the needle. As I understand, the clusters gets a speed signal from the car, then this map scales the output for the speedo stepper motor. And it doesn't have to be linear, correct? I see euro kmh speedos that go up to 260, but have 100 "straight up" instead of the expected 130. So there's one scale up to 100, and another for above 100 up to 260, right?

Is this all controlled by that one map? Specifically, I'm wondering, if I could have a custom MPH face made with a non-linear scale and mod the cluster to work with it.

What does this speedometer map actually do? What gets multiplied/divided/whatever to get the needle to point to a certain location?
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nyet
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« Reply #1 on: November 13, 2017, 02:01:15 PM »

When I read that a map is 8x1, 16 bit, what exactly does the 8x1 part mean?

I know what 16 bit is. I suspect 8x1 is like a one-dimensional array. Is that right? 8 of what, 16 bit values? So 16 bytes, or 128 bits?

So if some map were, let's say, 8x4, is that a two-dimensional array with 8 columns and 4 rows?

I've never messed with speedo calculations so I'll answer your map questions:

Yes. You are correct.

Furthermore:

A one dimensional array takes one input to generate one output.

A two dimensional array takes two inputs to generate one output.
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wmorri65
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« Reply #2 on: November 15, 2017, 11:21:46 AM »

Thanks, nyet.

Anybody know how the speedometer map works?
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