1. ## Another Scion TC steering wheel button thread

OK so I've read through all of the steering wheel button posts and I've gotten a few good results. I'll share my steps.

1. Found which/how many wires are used. (Two, Solution D )
2. Measure resistance for button presses, values are measured @20kOhms:
a. No press: 1.
b. Vol +: 0.99
c. Vol -: 3.1
d. Track +: 0.0
e. Track -: 0.33/ 0.32
f. Mode: No change. WTF?

I guess where I get retarded is... what are these values? If the multimeter is set at 20kOhms, does (a) give me a value of 20k? (b) 19800 (c) 62000 etc.

Also, any ideas as to why the MODE isn't showing up?

2. Hate to bump, but I guess I'm in need of some spoonfeeding.

3. Originally Posted by stealinfool
OK so I've read through all of the steering wheel button posts and I've gotten a few good results. I'll share my steps.

1. Found which/how many wires are used. (Two, Solution D )
2. Measure resistance for button presses, values are measured @20kOhms:
a. No press: 1.
b. Vol +: 0.99
c. Vol -: 3.1
d. Track +: 0.0
e. Track -: 0.33/ 0.32
f. Mode: No change. WTF?

I guess where I get retarded is... what are these values? If the multimeter is set at 20kOhms, does (a) give me a value of 20k? (b) 19800 (c) 62000 etc.

Also, any ideas as to why the MODE isn't showing up?
Multimeters dont output ratios, the 20k is just telling you where the decimal is and how many 0's to add after.

As to why mode shows nothing, that is impossible unless it is broken. What can happen is it is too low or too high for the 20k setting, so your multimeter shows nothing. Measure it with a smaller and larger range. And what nothing does it give? 0 or OL?

4. I've gone through the ranges and I think I at least have it figured out the range part. My highest value is 100.1k Ohm with no buttons pressed. Everything else is below that. I have 100k (5%) resistors already, I guess these will work?

The mode still isn't showing any results, though when I plug the stock stereo back in it functions properly. (I've merely piggy-backed off the wires in the harness, nothing's been cut) Is it possible that I've got a wire wrong? If so, how would I be getting a reading on the other buttons?

Here is my wiring diagram:

I'm using the pink and orange wires.

BTW when I have the radio plugged in and all the wires hooked up I get all sorts of crazy readings.

5. Originally Posted by stealinfool
I've gone through the ranges and I think I at least have it figured out the range part. My highest value is 100.1k Ohm with no buttons pressed. Everything else is below that. I have 100k (5%) resistors already, I guess these will work?

The mode still isn't showing any results, though when I plug the stock stereo back in it functions properly. (I've merely piggy-backed off the wires in the harness, nothing's been cut) Is it possible that I've got a wire wrong? If so, how would I be getting a reading on the other buttons?

Here is my wiring diagram:

I'm using the pink and orange wires.

BTW when I have the radio plugged in and all the wires hooked up I get all sorts of crazy readings.
If you have the schematic, it is pretty clear why MODE is not showing anything using your wires. You have a 3 wire system. MODE is on its own line for some reason. When you press MODE, only resistance is between SW2 and SWG. From your description you are measuring between SW1 and SWG.

You will require 2 inputs to the FB or you can combine MODE into SW1 with another value chosen that would put it outside the error range of buttons on SW1 already. Doesnt make sense to me why they would choose to do it that way since an extra port on the swivel ring thing the steering wheel uses for wires is much more costly than a few more resistors in a fancier network.

But anyways, you need a total of 3 wires, SW1 and SWG (what you have now) and SW2 and SWG (only for MODE).

6. For some reason, I'm getting totally different results from my first set of tests.

The green wire (not the light gray or LG) is allowing me a 2 wire setup with voltage just below 5vdc with a variation in output for all 5 buttons! WTF? Obviously this is easier now as I don't have to muck about with a voltage divider, but it makes no sense compared to what most people (with my car) have dealt with. Any ideas?

I'll be doing some more testing but it seems as if I can hook this up!

7. Well, I sound like an idiot here for sure, but I wasn't able to get any more DC readings when I went back to the car. I hadn't touched anything, either, so it was pretty weird.

Now that I'm using the green wire, I'm still able to get different readings for all five buttons.

My multimeter's highest settings go from 200k to 2M... with no buttons pressed it OL on 200k but reads .199 on 2M. I guess I'd be ok with getting a resister just above 200k?

8. Well I've finally got some time to play with this, and I'm becoming super frustrated.

I will start from the top.

I now get resistive measurements of
No buttons : 199k (only shows up at the 2M setting, not the 200k)
Vol Up : 101k
Vol Down : 103.1
Track Up : 100
Track Down : 100.3
Mode : 100.1

While those seem mighty close to me, I've tried every iteration of wiring possibility and these are the most consistent.

Now, I've got the FB wired up with the 220K resistor as follows

5v DC to 220K to FB input.

One side steering wheel wire to FB input

Other side steering wheel wire to vehicle ground

FB input ground to main FB/vehicle ground

(if this is not correct then I assume the following does not matter)

Initially i was getting these voltages with the original control center code:
No press 2.37
Vol + 1.57
Vol - 1.59
Track + 1.56
Track - 1.56
Mode 1.56

I goofed it up and now I'm using the code borrowed from this post in the tutorial, though I've trimmed it down to just my analog input/logic.

Now the voltages range so much and change so fast I'm having trouble pinning down my ranges. I've adjusted my timers (currently at 30ms) and set auto average to true (history to 5). That has helped, but not much. How can I tame this? And will I be able to get accurate enough measurements to divide them up into separate logics?

9. Originally Posted by stealinfool
Well I've finally got some time to play with this, and I'm becoming super frustrated.

I will start from the top.

I now get resistive measurements of
No buttons : 199k (only shows up at the 2M setting, not the 200k)
Vol Up : 101k
Vol Down : 103.1
Track Up : 100
Track Down : 100.3
Mode : 100.1

While those seem mighty close to me, I've tried every iteration of wiring possibility and these are the most consistent.

Now, I've got the FB wired up with the 220K resistor as follows

5v DC to 220K to FB input.

One side steering wheel wire to FB input

Other side steering wheel wire to vehicle ground

FB input ground to main FB/vehicle ground

(if this is not correct then I assume the following does not matter)

Initially i was getting these voltages with the original control center code:
No press 2.37
Vol + 1.57
Vol - 1.59
Track + 1.56
Track - 1.56
Mode 1.56

I goofed it up and now I'm using the code borrowed from this post in the tutorial, though I've trimmed it down to just my analog input/logic.

Now the voltages range so much and change so fast I'm having trouble pinning down my ranges. I've adjusted my timers (currently at 30ms) and set auto average to true (history to 5). That has helped, but not much. How can I tame this? And will I be able to get accurate enough measurements to divide them up into separate logics?

You should not have to use the 2M mode on your meter. That means 2 MegaOhms meaning value x 1000000 ohms. Waaaaaaaay to high.

You are probably measuring the resistance of the input port or something on an IC somewhere down the line, because that sounds about right for that. Completely meaningless though.

You do not have the stock radio connected? If you connect the stock radio, resistances will not be correct.

And those voltages are too close together to do anything with.

Go back to step one.

Disconnect radio, measure between SW1/SW2 and SWG with the buttons pressed. I very much doubt the values are out of the kOhm range.

10. Well, it turns out that I am, in fact, retarded. I am back to using a configuration that is close to what I had a few days ago. I have finally got everything up and running, monitoring voltages easily and effectively in MDX. Once I get it all set up and soldered/crimped I'll post my final configuration to help any future not-so-smart fellow tC owners.

Thanks for your help there 2k1, I may be bothering you about some RR COM stuff in the near future.

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