Fusion brain with 3000GT Steering Wheel Controls

**TerraWombat** · 02-21-2008, 03:56 PM

Was wondering if I could use the Fusion Brain in conjunction with my factory steering wheel controls (on a 1991 Mits 3000GT) and my carPC. I'd like to retain the volume up/down and mute buttons on the steering wheel to control the volume up/down and mute in WinXP. The problem I see so far is that my controls are not the "resistive wire" type. There are only two wires going into the controls (power and ground), but pressing the buttons does nothing to the voltage. Using an oscilloscope, each button produces a unique pulse train with a frequency of about 1.2 milliseconds (low for .4 milliseconds and high for .8 milliseconds). Does this sort of radio control sound like it could be programmed the way I'd like with the Fusion Brain?

**TerraWombat** · 02-21-2008, 06:27 PM

Here is some information regarding the pulse trains for the different buttons:

Mute: 1111101011111
FM/AM: 1111010111111
Vol -: 1111011101111
Vol +: 111111101111
Auto M: 11110110101111
M Cal: 1111110101111

Each pulse has a duration (frequency) of about 1.2 milliseconds. It is pulled low for approximately .4 milliseconds and high for about .8 milliseconds. Each button is represented by 13 - 15 pulses. Once the last pulse occurs, the signal stays high for 13-16 mlliseconds and then the signal repeats. The signal repeats every 29 milliseconds (regardless of which button).

Two buttons are oddballs. The Vol + button has 13 recognizable pulses and the Auto M button has 15 recognizable pulses. To me this would imply that all buttons output a code of 15 pulses (or more) but there are leading or trailing pulses that cannot be seen by the scope because they are off.

**greenman100** · 02-21-2008, 07:50 PM

Unfortunately, the Brain samples analog inputs about every 10mS... so it wouldn't be fast enough to do what you're looking for.

I suppose you could retrofit your conttols to resistive type....

**TerraWombat** · 02-22-2008, 12:20 AM

Originally Posted by greenman100

Unfortunately, the Brain samples analog inputs about every 10mS... so it wouldn't be fast enough to do what you're looking for.

I suppose you could retrofit your controls to resistive type....

Thank you for the response. Changing them over to a resistive type is an option, but I'm still on the lookout for a PIC that will be able to accept the factory buttons and the wacky signals they send. Once I get these to work, I plan on using the cruise control lever on the steering wheel for additional shortcut keys for my carPC (I deleted cruise control on my car long ago).

**greenman100** · 02-22-2008, 01:27 AM

The trouble is, USB can update at best every 1mS.... so with the PIC acting as a blind capture device, best case scenario you can do 1mS refreshes.

What you'd need is a PIC that capture the signals, buffer them, and send them... if we spent the processing power to do this, it would hurt our analog input refresh rates.