Code used to take 1.2L intake air temperature sensor reading and turn it into a resistance to be shown to the Insight ECU. For the time being I've decided to show the Insight ECU a constant resistance value (a constant temperature in other words). There really is no reason to tell the Insight ECU the real temperature as we're not trying to run the Honda engine. If the Insight ECU does for some reason require the real temperature then the mathematical relationship need an update as the variation with temperature is non-linear.
/** Lupo to Insight Intake Air Temperature (IAT) Conversion
* by Jake Staub
*
* Takes the Lupo IAT voltage signal, converts it to a temperature,
* then turns the temperature into the required Insight resistance
* value.
* Lupo temp(volt) = m1*volt + b1.
* Insight res(temp) = m2*temp + b2.
*/
int IATvolt = 2; // Lupo IAT sensor input pin
int val = 0; // variable to store the value coming from the Lupo IAT sensor
float volt = 0; // variable to store Lupo analog voltage value
int fractional; // variable to store fractional value
int temp = 0; // variable to store Lupo analog temperature value
int res = 0; // variable to strore Insight analog resistance value
int m1 = -44; // slope for Lupo temperature function
int b1 = 186; // y intercept for Lupo temperature function
int m2 = -89; // slope for Insight resistance function
int b2 = 8800; // y intercept for Insight resistance function
void setup() {
Serial.begin(9600); // opens serial port for debugging
}
void loop() {
val = analogRead(IATvolt); // reads the value from the sensor
volt = val / 204.8; // converts digital val to analog volt
val = val / 205; // converts digital val to analog val
fractional = (volt - val)*1000; // calculates decimal voltage value
Serial.print("volt = "); // prints "volt = "
Serial.print(val); // prints integer volt value
Serial.print("."); // prints "."
Serial.println(fractional); // prints decimal volt value
delay(3000); // 3 second delay (3000 ms)
temp = m1*volt + b1; // Lupo temperature as a function of voltage
Serial.print("temp = "); // prints "temp = "
Serial.println(temp); // prints analog temperature value
delay(3000); // 3 second delay (3000 ms)
res = m2*temp + b2; // Insight resistance as a function of temperature
if (res < 100) // limits low resistance value
{res = 100;} // 100 ohm minimum resistance
Serial.print("res = "); // prints "res = "
Serial.println(res); // prints analog resistance value
delay(3000); // 3 second delay (3000 ms)
}
