# Speed Signal measuring

A project log for JVC to Clio

I want to use a JVC car radio with Renault Clio's built-in steering wheel remote

I measured values on pin A1 of the ISO 10487 connector.

Here you are the measured values:

 Speed (km/h) Pulse duration (μs) 30 ~13000 40 ~10000 50 ~7700 70 ~5400 90 ~4200 100 ~3750 100 ~3400 120 ~3200

It can be calculated more accurate values with "distance = speed x time" formula. It seems the distance is around 0,105m. I this case the duration are the followings:

 Speed (km/h) Pulse duration (μs) 30 12600 40 9450 50 7560 70 5400 90 4200 100 3780 110 3436 120 3150 140 2700 150 2520

The arduino program for the measuring was the following:

```/*
ISO 10487 defines a standard for connectors for the head unit to the car's electrical system, consisting of a system of four different connectors typically used in head units for car audio.
Power (A)
+-----------------+
| |1  |3  |5  |7  |
_|                 |
|_  |2  |4  |6  |8  |
+-----------------+

A1 Speed signal
A2 Phone mute
A3 Not connected
A4 +12v battery
A5 Antenna motor
A6 Illumination
A7 +12v switched
A8 Ground

***

+---+
+------|USB|------+
|[ ]J1 +---+      |
|( )TX0     RAW( )|  RAW
|( )RXI     GND( )|  GND
GND  |( )GND     RST( )|  RESET
GND  |( )GND     VCC( )|  VCC
|( )2        A3( )|
INT0  |( )3   /\   A2( )|
|( )4  /  \  A1( )|
|( )5  \  /  A0( )|
|( )6   \/   15( )|  SCK
|(X)7        14( )|  MISO
|( )8        16( )|  MOSI
|( )9        10( )|
+-----------------+
ProMicro
*/

int SignalPin = 7;
unsigned long duration;

void setup()
{
Serial.begin(9600);
pinMode(SignalPin, INPUT_PULLUP);
}

void loop()
{
duration = pulseIn(SignalPin, LOW);
Serial.println(duration);
delay(1000);
}```

I forgot to mention that there was a 4N25 optocoupler on pin7. I will attach some pictures about my prototype board soon...