tachometer.cpp

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/*
 * @file tachometer.cpp
 * @brief This is about driving external analog tachometers
 *
 * This implementation produces one pulse per engine cycle
 *
 * @date Aug 18, 2015
 * @author Andrey Belomutskiy, (c) 2012-2020
 */
 
#include "pch.h"
 
#include "tachometer.h"
 
static SimplePwm tachControl("tach"); 
static float tachFreq;  
static float duty;   
 
#if EFI_UNIT_TEST
float getTachFreq() {
    return tachFreq;
}
 
float getTachDuty() {
    return duty;
}
#endif
 
static bool tachHasInit = false;
 
void tachUpdate() {
    // Only do anything if tach enabled
    if (!tachHasInit) {
        return;
    }
 
    // How many tach pulse periods do we have?
    int periods = engineConfiguration->tachPulsePerRev;
 
    if (periods == 0 || periods > 10) {
        firmwareError(ObdCode::CUSTOM_ERR_6709, "Invalid tachometer pulse per rev: %d", periods);
        return;
    }
 
    // What is the angle per tach output period?
    float cycleTimeMs = 60000.0f / Sensor::getOrZero(SensorType::Rpm);
    float periodTimeMs = cycleTimeMs / periods;
    tachFreq = 1000.0f / periodTimeMs;
    
    if (engineConfiguration->tachPulseDurationAsDutyCycle) {
        // Simple case - duty explicitly set
        duty = engineConfiguration->tachPulseDuractionMs;
    } else {
        // Constant high-time mode - compute the correct duty cycle
        duty = engineConfiguration->tachPulseDuractionMs / periodTimeMs;
    }
 
    // In case Freq is under 1Hz, we stop pwm to avoid warnings!
    if (tachFreq < 1) {
        tachFreq = NAN;
    }
    
    tachControl.setSimplePwmDutyCycle(duty);
    tachControl.setFrequency(tachFreq);
}
 
void initTachometer() {
    tachHasInit = false;
 
    if (!isBrainPinValid(engineConfiguration->tachOutputPin)) {
        return;
    }
 
    startSimplePwm(&tachControl,
                "Tachometer",
                &engine->executor,
                &enginePins.tachOut,
                NAN, 0.1f);
 
    tachHasInit = true;
}