# Thread: Tutorial - Steering Wheel Controls

1. ## Tutorial - Steering Wheel Controls

Steering Wheel Interface Tutorial

So, you want to hook up that new Fusion Brain to your steering wheel controls, eh?

First, let's review a bit about electricity. There are three aspects that are particularly important:

• Voltage - electrical "push", like pressure in a pipe (measured in AC or DC volts)
• Current - electrical "quantity", like flowrate in a pipe (measured in amps)
• Resistance - electrical "restriction", like a blockage in a pipe (measured in ohms)

And some mathematical prefixes:

• (u) - micro - 10^-6 - .000001
• (m) - milli - 10^-3 - .001
• (k) - kilo - 10^3 - 1000
• (M) - mega - 10^6 - 1,000,000

Then, get your wiring diagram for your car, and locate the steering wheel wire(s).

Now that we have that squared away, get out your multimeter. You have a multimeter, right?

Set that baby to DC volts, as shown in the picture. If your meter doesn't have auto-scaling, set it to 20Volts DC.

If you have one steering wheel wire, follow these steps
1. Turn the car's ignition to on. (not running)
2. Connect the negative terminal of your meter to ground. (it's the black probe, as can be seen above) make sure you use a good ground. If you use a poor ground, all your measurements will be bad. A good source for ground is the ground/negative wire feeding the brain in your car.
3. Connect the positive terminal to the wire you found earlier with your wiring diagram.
4. Record the voltage (if any) for no buttons pressed, and each button individually.
5. If you get voltages in the range of 0.5volts to 5 volts, proceed to solution A.
6. If you get voltages in the range of 0.5volts to 12 volts, proceed to solution B.
7. If you get voltages less than 0.5 volts, proceed to solution C

If you have two steering wheel wires, follow these steps
1. Turn the car's ignition to on. (not running)
2. Connect the negative terminal of your meter to ground. (it's the black probe, as can be seen above) make sure you use a good ground. If you use a poor ground, all your measurements will be bad. A good source for ground is the ground/negative wire feeding the brain in your car.
3. Connect the positive terminal one of the wires you found earlier with your wiring diagram.
4. Record the voltage (if any) for no buttons pressed, and each button individually.
5. If you get voltages in the range of 0.5volts to 5 volts, proceed to solution A.
6. If you get voltages in the range of 0.5volts to 12 volts, proceed to solution B.
7. If you get voltages less than 0.5 volts, repeat steps 3-6, but connect positive terminal to other steering wheel wire
8. If you do step 7 and still get no voltages, proceed to solution D.

Solution A
You don't need anything at all! Just connect the steering wheel wire (the one connected to the positive terminal of your meter earlier) to the input on the brain (the outermost pin, away from the center of the board) You're done!

Solution B
Congrats! All you need is a voltage divider.

Here is a simple voltage divider:

Vin is what you want to measure, Vout goes to the input pin of the brain (towards the edge of the board) and the symbol at the bottom indicates ground. R1 and R2 need to be selected on a application by application basis.

This formula will help select R1 and R2. For the Fusion Brain, it is a good idea to keep R1 and R2 under 1k-ohm.

We will assume 15vDC maximum, to allow headroom for voltage spikes.

Vout = 100/(200+100)*Vin
5 = 1/4*20

so the voltage divider, with a 200ohm R1 and a 100ohm R2, would have a scaling factor of 33%, meaning we could measure up to 15vDC without overloading the brain... perfect for car applications.

Installation of voltage divider:
Use the diagram above, but connect your steering wheel wire (the one connected to the positive terminal of your meter earlier) to Vin, and connect Vout to the input on the brain (the outermost pin, away from the center of the board) You're done!

Solution C
Solution C is a bit more complicated. Basically, your steering wheel system is the one wire resistive type. We need to find out what the maximum resistance is. The Fusion Brain cannot measure resistance directly, so we must put the steering wheel into a voltage divider configuration, similar to above.

Set your meter to a resistive scale. Generally, 20kohms is a good place to start.

1. Turn the car's ignition to on. (not running)
2. Connect the negative terminal of your meter to ground. (it's the black probe, as can be seen above) make sure you use a good ground. If you use a poor ground, all your measurements will be bad. A good source for ground is the ground/negative wire feeding the brain in your car.
3. Connect the positive terminal one of the wires you found earlier with your wiring diagram.
4. Record the resistance (if any) for no buttons pressed, and each button individually.

Take the highest resistance recorded, and go to radioshack and buy a similar value. For instance, if the highest resistance was 44kohms, you'd want to buy a 47kohm resistor. That resistor you bought becomes R1 in the following figure:

And your steering wheel is R2. The internals of your steering wheel are already connected to ground, so connect the steering wheel wire to the input of the brain and one side of R1, and connect the other side of R1 to the +5vDC pin on the brain's analog input header (towards the center of the board). You're done!

Solution D
Solution D is even more complicated. Basically, your steering wheel system is the two wire resistive type. We need to find out what the maximum resistance is. The Fusion Brain cannot measure resistance directly, so we must put the steering wheel into a voltage divider configuration, similar to above.

Set your meter to a resistive scale. Generally, 20kohms is a good place to start.

1. Turn the car's ignition to on. (not running)
2. Connect the negative terminal of your meter to one steering wheel wire.
3. Connect the positive terminal the other steering wheel wire.
4. Record the resistance (if any) for no buttons pressed, and each button individually.

Take the highest resistance recorded, and go to radioshack and buy a similar value. For instance, if the highest resistance was 44kohms, you'd want to buy a 47kohm resistor. That resistor you bought becomes R1 in the following figure:

And your steering wheel is R2. Connect one steering wheel wire to ground, and the other the steering wheel wire to the input of the brain and one side of R2. Connect the other side of R2 to the +5vDC pin on the brain's analog input header (towards the center of the board). You're done!

Once finished, fire up the fusion brain, and make a skin that measures the input you hooked up. Press each button individually, and record the voltage the brain reads. They should range over 0-5vDC. If you'd like, you can use the Fusion software to control other programs with your steering wheel buttons. For information on that, please refer to our software documentation.

2. Fixed wording.

3. Ok hopefully you don't mind us n00bs posting in your fancy tutorial thread.

I'm basically clueless when it comes to electronics so I was hoping you could explain things again for me.

I have solution D. I've been able to measure the resistance across two pins in the wiring harness where the old head unit used to be. The resistances range from 1474ohms to 84ohms. Does this sound correct? The values are a lot lower than the ones you used in your tutorial.

From here I was hoping you could explain in a bit more depth what to hook up to where in terms a simpleton like me could understand. I didn't quite follow the wording used when you said

Connect one steering wheel wire to ground, and the other the steering wheel wire to the input of the brain and one side of R2. Connect the other side of R2 to the +5vDC pin on the brain's analog input header (towards the center of the board). You're done!

Any help would be greatly appreciated.

4. Those resistances sound fine... the values in my tutorial are arbitrary.

one of the steering wheel wires ---> ground

the other wire ---> the input pin of the fusion brain

one side of R2 (resistor 2) ---> the 5volt pin of the brain

the other side of R2 ---> the input pin of the fusion brain

does that help?

5. Yep perfect, even I can understand that

Hopefully I don't blow up my fusion brain.

6. You have to try pretty hard to damage it... and if you do, we'll work with you on it.

7. For the software side of this:

1) Create a Fusion Brain Instnace to the Fusion Brain the steering wheel wire will be connected to
2) Create an Analogue Input Instance
a) Set the port to the port you will connect to wire to. (0 index based)
b) Set auto-average to 0, or at most a value of 5 or else your presses will "linger" and trigger multiple button presses
3) Create a Logic Node for each button you want to map by doing...
a) Place down your analogue input module, and a number module with the lowest value recorded for that button and a little less (but not so much less it hits the upper bound of another button).
b) Drop down a greater than or equal to module
c) Connect the analogue input module to the top node of the greater than module, and connect the number module to the lower node of the greater than module.
d) Place down your analogue input module (same as step a), and a number module with the highest value recorded for that button and a little more (but not so much more it hits the lower bound of another button).
e) Drop down a less than or equal to module
f) Connect the analogue input module to the top node of the less than module, and connect the number module to the lower node of the less than module.
g) Drop down an AND module
h) Connect the greater than module and the less than module to the AND module in any order (AND is not picky)
i) Place the logic output module (big arrow) and connect to the output of the AND module to finish the complete if/then statement
j) Click the Then/Do icon to add/edit then do statements
k) Add a then do statement to send a key
I) EITHER choose "send key" and then setup the target ID and class of the window you want to send to. This will seek out that window, and target a keypress to that window only.
II) OR choose "send key to foreground" and then choose your key. This will send a key blindly to whatever application is ontop, with no control that way. If the app is not ontop and focused or does not accept global hotkeys, nothing will happen.
l) Choose the properties, and name it so you can keep track
m) Choose it to fire on a timer (logic timer is a good choice for this)
n) Set a minimum delta vote time. This is the time between votes (key presses). Because you will probably be reading the ports in every 50ms or so, but that would cause some crazy keys to be send every 50ms. So set the vote time to something that works for you like 500ms, or 1000ms (1 second). You will need to play with this, and can be different for each button. Maybe Play/Pause should be higher than say Fastforward which should be shorter. All user configurable
o) Save If/Then node
4) Save file in MDX directory, and run MDX, and enjoy.

8. I am having trouble following this tutorial. does this tutorial differ from a current version of MDX Configurator?

9. The Autozone website has wiring schematics for a decent selection of vehicles. The schematics available will probably include the basic steering controls for your make and model. Best of all, these are FREE for download.

You will need to accept cookies for the site.

http://www.autozone.com/shopping/repairGuide.htm

Fill in the year, make, model, and then any other filter (usually engine).

Select "Wiring Diagrams" from the list of links. This will bring up a list of various schematics for your vehicle.

Most of the radio control info is listed under "Entertainment". Other buttons on the steering wheel will probably be listed under "HVAC systems" or the "Instrument Cluster" links.

.

10. Originally Posted by Urbanmindz
I am having trouble following this tutorial. does this tutorial differ from a current version of MDX Configurator?
No. The configurator has not changed anything in this tutorial. Only things that have been added have nothing to do with this.

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