Speed Sensitive Volume w/ AppRadio4
 

I really miss the vehicle speed adjustments to the audio with the original head unit and I'd like to attempt to recreate this feature with my new AppRadio4 headunit.

I have an idea on how to get this feature back and wanted to know what you guys thought.

Tap into the VSS (Vehicle Speed Sensor) wire and depending on the speed, a different voltage is sent through the wire.

Using an arduino, receive the voltage from the VSS as input and create "map" in software that accepts the different voltages, and maps those out to different volume up or down commands that can be sent to the hard wired steering wheel control input on the back on the headunit.

What I'll need to do is understand what is going across the wire when a vol up and down is pressed and be able to recreate that with the arduino, again using the VSS voltage changes as input.


Does this makes sense? Also, has anyone attempted to do something similar with their "86"?

Update: Looks like rather than a specific voltage being applied, its a pulse that switches on and off so many times a sec. The number of times it pulses in a given time frame determines the speed. So ill have to find out what the appropriate pulse values are for certain speeds.

Found the following on the Arduino forum:

#define DIV 120
#define FPM 5280
#define TIRCIR 7.56
#define PPR 123.2
long TIME = 1000000;//time constant to divide freq
long vsspulse = pulseIn(vss, HIGH);
float vssval = (vsspulse / TIME);
float MPHpulse = ((1 / vssval)/ 2);
byte MPH = ((MPHpulse / FPM) * (TIRCIR / PPR) * DIV);

The issue is that the Arduino does not know what volume your head unit is already at so it would be annoying if you are already blasting your music going 20mph. Then you will be deaf by the time you hit 60mph