/*
 * fsm-adc.c: ADC (voltage, temperature) functions for SpaghettiMonster.
 *
 * Copyright (C) 2017 Selene ToyKeeper
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef FSM_ADC_C
#define FSM_ADC_C


static inline void set_admux_therm() {
    #if (ATTINY == 1634)
        ADMUX = ADMUX_THERM;
    #elif (ATTINY == 25) || (ATTINY == 45) || (ATTINY == 85)
        ADMUX = ADMUX_THERM;
    #elif (ATTINY == 841)  // FIXME: not tested
        ADMUXA = ADMUXA_THERM;
        ADMUXB = ADMUXB_THERM;
    #else
        #error Unrecognized MCU type
    #endif
    adc_channel = 1;
    adc_sample_count = 0;  // first result is unstable
    ADC_start_measurement();
}

inline void set_admux_voltage() {
    #if (ATTINY == 1634)
        #ifdef USE_VOLTAGE_DIVIDER // 1.1V / pin7
            ADMUX = ADMUX_VOLTAGE_DIVIDER;
        #else  // VCC / 1.1V reference
            ADMUX = ADMUX_VCC;
        #endif
    #elif (ATTINY == 25) || (ATTINY == 45) || (ATTINY == 85)
        #ifdef USE_VOLTAGE_DIVIDER  // 1.1V / pin7
            ADMUX = ADMUX_VOLTAGE_DIVIDER;
        #else  // VCC / 1.1V reference
            ADMUX = ADMUX_VCC;
        #endif
    #elif (ATTINY == 841)  // FIXME: not tested
        #ifdef USE_VOLTAGE_DIVIDER  // 1.1V / pin7
            ADMUXA = ADMUXA_VOLTAGE_DIVIDER;
            ADMUXB = ADMUXB_VOLTAGE_DIVIDER;
        #else  // VCC / 1.1V reference
            ADMUXA = ADMUXA_VCC;
            ADMUXB = ADMUXB_VCC;
        #endif
    #else
        #error Unrecognized MCU type
    #endif
    adc_channel = 0;
    adc_sample_count = 0;  // first result is unstable
    ADC_start_measurement();
}

inline void ADC_start_measurement() {
    #if (ATTINY == 25) || (ATTINY == 45) || (ATTINY == 85) || (ATTINY == 841) || (ATTINY == 1634)
        ADCSRA |= (1 << ADSC) | (1 << ADIE);
    #else
        #error unrecognized MCU type
    #endif
}

// set up ADC for reading battery voltage
inline void ADC_on()
{
    #if (ATTINY == 25) || (ATTINY == 45) || (ATTINY == 85) || (ATTINY == 1634)
        set_admux_voltage();
        #ifdef USE_VOLTAGE_DIVIDER
            // disable digital input on divider pin to reduce power consumption
            DIDR0 |= (1 << VOLTAGE_ADC_DIDR);
        #else
            // disable digital input on VCC pin to reduce power consumption
            //DIDR0 |= (1 << ADC_DIDR);  // FIXME: unsure how to handle for VCC pin
        #endif
        #if (ATTINY == 1634)
            //ACSRA |= (1 << ACD);  // turn off analog comparator to save power
            //ADCSRB |= (1 << ADLAR);  // left-adjust flag is here instead of ADMUX
        #endif
        // enable, start, auto-retrigger, prescale
        ADCSRA = (1 << ADEN) | (1 << ADSC) | (1 << ADATE) | ADC_PRSCL;
        // end tiny25/45/85
    #elif (ATTINY == 841)  // FIXME: not tested, missing left-adjust
        ADCSRB = 0;  // Right adjusted, auto trigger bits cleared.
        //ADCSRA = (1 << ADEN ) | 0b011;  // ADC on, prescaler division factor 8.
        set_admux_voltage();
        // enable, start, auto-retrigger, prescale
        ADCSRA = (1 << ADEN) | (1 << ADSC) | (1 << ADATE) | ADC_PRSCL;
        //ADCSRA |= (1 << ADSC);  // start measuring
    #else
        #error Unrecognized MCU type
    #endif
}

inline void ADC_off() {
    ADCSRA &= ~(1<<ADEN); //ADC off
}

#ifdef USE_VOLTAGE_DIVIDER
static inline uint8_t calc_voltage_divider(uint16_t value) {
    // use 9.7 fixed-point to get sufficient precision
    uint16_t adc_per_volt = ((ADC_44<<7) - (ADC_22<<7)) / (44-22);
    // shift incoming value into a matching position
    uint8_t result = ((value>>1) / adc_per_volt) + VOLTAGE_FUDGE_FACTOR;
    return result;
}
#endif

// Each full cycle runs ~4X per second with just voltage enabled,
// or ~2X per second with voltage and temperature.
#if defined(USE_LVP) && defined(USE_THERMAL_REGULATION)
#define ADC_CYCLES_PER_SECOND 2
#else
#define ADC_CYCLES_PER_SECOND 4
#endif

// happens every time the ADC sampler finishes a measurement
// collects a rolling average of 64+ samples, which increases effective number
// of bits from 10 to about 16 (ish, probably more like 14 really) (64 was
// chosen because it's the largest sample size which allows the sum to still
// fit into a 16-bit integer, and for speed and size reasons, we want to avoid
// doing 32-bit math)
ISR(ADC_vect) {

    static uint16_t adc_sum;

    // keep this moving along
    adc_sample_count ++;

    // reset on first sample
    // also, ignore first value since it's probably junk
    if (1 == adc_sample_count) {
        adc_sum = 0;
        return;
    }
    // 64 samples collected, save the result
    // (actually triggers at 64 and every 32 afterward)
    else if (66 == adc_sample_count) {
        // save the latest result
        adc_smooth[adc_channel] = adc_sum;
        // cut sum in half and set up another half-window of samples
        // (for sort of a continuous average)
        // (this seems to significantly reduce noise)
        adc_sum >>= 1;
        adc_sample_count = 33;
    }
    // add the latest measurement to the pile
    else {
        uint16_t m = ADC;
        // add to the running total
        adc_sum += m;
        // update the latest value
        adc_raw[adc_channel] = m;
    }

    // track what woke us up, and enable deferred logic
    irq_adc = 1;
}

void adc_deferred() {
    irq_adc = 0;  // event handled

    #ifdef USE_PSEUDO_RAND
    // real-world entropy makes this a true random, not pseudo
    // Why here instead of the ISR?  Because it makes the time-critical ISR
    // code a few cycles faster and we don't need crypto-grade randomness.
    pseudo_rand_seed += ADCL;
    #endif

    // the ADC triggers repeatedly when it's on, but we only need to run the
    // voltage and temperature regulation stuff once in a while...so disable
    // this after each activation, until it's manually enabled again
    if (! adc_deferred_enable) return;

    // disable after one iteration
    adc_deferred_enable = 0;

    // what is being measured? 0 = battery voltage, 1 = temperature
    uint8_t adc_step;

    #if defined(USE_LVP) && defined(USE_THERMAL_REGULATION)
    // do whichever one is currently active
    adc_step = adc_channel;
    #else
    // unless there's no temperature sensor...  then just do voltage
    adc_step = 0;
    #endif

    #if defined(TICK_DURING_STANDBY) && defined(USE_SLEEP_LVP)
        // in sleep mode, turn off after just one measurement
        // (having the ADC on raises standby power by about 250 uA)
        // (and the usual standby level is only ~20 uA)
        if (go_to_standby) {
            ADC_off();
            // also, only check the battery while asleep, not the temperature
            adc_channel = 0;
        }
    #endif

    if (0) {} // placeholder for easier syntax

    #ifdef USE_LVP
    else if (0 == adc_step) {  // voltage
        ADC_voltage_handler();
        #ifdef USE_THERMAL_REGULATION
        // set the correct type of measurement for next time
        if (! go_to_standby) set_admux_therm();
        #endif
    }
    #endif

    #ifdef USE_THERMAL_REGULATION
    else if (1 == adc_step) {  // temperature
        ADC_temperature_handler();
        #ifdef USE_LVP
        // set the correct type of measurement for next time
        set_admux_voltage();
        #endif
    }
    #endif
}


#ifdef USE_LVP
static inline void ADC_voltage_handler() {
    // rate-limit low-voltage warnings to a max of 1 per N seconds
    static uint8_t lvp_timer = 0;
    #define LVP_TIMER_START (VOLTAGE_WARNING_SECONDS*ADC_CYCLES_PER_SECOND)  // N seconds between LVP warnings

    uint16_t measurement;

    // latest ADC value
    if (go_to_standby) measurement = adc_raw[0] << 6;
    else measurement = adc_smooth[0];

    #ifdef USE_VOLTAGE_DIVIDER
    voltage = calc_voltage_divider(measurement);
    #else
    // calculate actual voltage: volts * 10
    // ADC = 1.1 * 1024 / volts
    // volts = 1.1 * 1024 / ADC
    voltage = ((uint16_t)(2*1.1*1024*10)/(measurement>>6) + VOLTAGE_FUDGE_FACTOR) >> 1;
    #endif

    // if low, callback EV_voltage_low / EV_voltage_critical
    //         (but only if it has been more than N seconds since last call)
    if (lvp_timer) {
        lvp_timer --;
    } else {  // it has been long enough since the last warning
        if (voltage < VOLTAGE_LOW) {
            // send out a warning
            emit(EV_voltage_low, 0);
            // reset rate-limit counter
            lvp_timer = LVP_TIMER_START;
        }
    }
}
#endif


#ifdef USE_THERMAL_REGULATION
static inline void ADC_temperature_handler() {
    // thermal declarations
    #ifndef THERMAL_UPDATE_SPEED
    #define THERMAL_UPDATE_SPEED 2
    #endif
    #define NUM_THERMAL_VALUES_HISTORY 8
    static uint8_t history_step = 0;  // don't update history as often
    static uint16_t temperature_history[NUM_THERMAL_VALUES_HISTORY];
    static uint8_t temperature_timer = 0;
    #define TEMPERATURE_TIMER_START (THERMAL_WARNING_SECONDS*ADC_CYCLES_PER_SECOND)  // N seconds between thermal regulation events

    // latest 16-bit ADC reading
    uint16_t measurement;

    if (! reset_thermal_history) {
        // average of recent samples
        measurement = adc_smooth[1];
    } else {  // wipe out old data
        // don't keep resetting
        reset_thermal_history = 0;

        // ignore average, use latest sample
        measurement = adc_raw[1] << 6;

        // forget any past measurements
        for(uint8_t i=0; i<NUM_THERMAL_VALUES_HISTORY; i++)
            temperature_history[i] = measurement;
    }

    {  // rotate the temperature history
        // if it's time to rotate the thermal history, do it
        // FIXME? allow more than 255 frames per step
        //        (that's only about 8 seconds maximum)
        history_step ++;
        #if (THERMAL_UPDATE_SPEED == 4)  // new value every 4s
        #define THERM_HISTORY_STEP_MAX (4*ADC_CYCLES_PER_SECOND)
        #elif (THERMAL_UPDATE_SPEED == 2)  // new value every 2s
        #define THERM_HISTORY_STEP_MAX (2*ADC_CYCLES_PER_SECOND)
        #elif (THERMAL_UPDATE_SPEED == 1)  // new value every 1s
        #define THERM_HISTORY_STEP_MAX (ADC_CYCLES_PER_SECOND)
        #elif (THERMAL_UPDATE_SPEED == 0)  // new value every 0.5s
        #define THERM_HISTORY_STEP_MAX (ADC_CYCLES_PER_SECOND/2)
        #endif
        // FIXME: rotate the index instead of moving the values
        if (THERM_HISTORY_STEP_MAX == history_step) {
            history_step = 0;
            // rotate measurements and add a new one
            for (uint8_t i=0; i<NUM_THERMAL_VALUES_HISTORY-1; i++) {
                temperature_history[i] = temperature_history[i+1];
            }
            temperature_history[NUM_THERMAL_VALUES_HISTORY-1] = measurement;
        }
    }

    // let the UI see the current temperature in C
    // Convert ADC units to Celsius (ish)
    temperature = (measurement>>6) - 275 + THERM_CAL_OFFSET + (int16_t)therm_cal_offset;

    // guess what the temperature will be in a few seconds
    int16_t pt;
    {
        int16_t diff;
        uint16_t t = measurement;

        // algorithm tweaking; not really intended to be modified
        // how far ahead should we predict?
        #ifndef THERM_PREDICTION_STRENGTH
        #define THERM_PREDICTION_STRENGTH 4
        #endif
        // how proportional should the adjustments be?  (not used yet)
        #ifndef THERM_RESPONSE_MAGNITUDE
        #define THERM_RESPONSE_MAGNITUDE 128
        #endif
        // acceptable temperature window size in C
        #define THERM_WINDOW_SIZE (3<<6)
        // highest temperature allowed
        #define THERM_CEIL (((int16_t)therm_ceil)<<6)
        // bottom of target temperature window
        #define THERM_FLOOR (THERM_CEIL - THERM_WINDOW_SIZE)

        // guess what the temp will be several seconds in the future
        // diff = rate of temperature change
        diff = t - temperature_history[0];
        // slight bias toward zero; ignore very small changes (noise)
        /*
        // FIXME: this is way too small for 16-bit values
        for (uint8_t z=0; z<3; z++) {
            if (diff < 0) diff ++;
            if (diff > 0) diff --;
        }
        */
        // projected_temperature = current temp extended forward by amplified rate of change
        pt = projected_temperature = t + (diff<<THERM_PREDICTION_STRENGTH);
    }

    if (temperature_timer) {
        temperature_timer --;
    } else {  // it has been long enough since the last warning

        // Too hot?
        if (pt > THERM_CEIL) {
            // reset counters
            temperature_timer = TEMPERATURE_TIMER_START;
            // how far above the ceiling?
            //int16_t howmuch = (pt - THERM_CEIL) * THERM_RESPONSE_MAGNITUDE / 128;
            int16_t howmuch = (pt - THERM_CEIL) >> 6;
            // send a warning
            emit(EV_temperature_high, howmuch);
        }

        // Too cold?
        else if (pt < THERM_FLOOR) {
            // reset counters
            temperature_timer = TEMPERATURE_TIMER_START;
            // how far below the floor?
            //int16_t howmuch = (THERM_FLOOR - pt) * THERM_RESPONSE_MAGNITUDE / 128;
            int16_t howmuch = (THERM_FLOOR - pt) >> 6;
            // send a notification (unless voltage is low)
            // (LVP and underheat warnings fight each other)
            if (voltage > VOLTAGE_LOW)
                emit(EV_temperature_low, howmuch);
        }

        // Goldilocks?  (temperature is within target window)
        else {
            // reset counters
            temperature_timer = TEMPERATURE_TIMER_START;
            // send a notification (unless voltage is low)
            // (LVP and temp-okay events fight each other)
            if (voltage > VOLTAGE_LOW)
                emit(EV_temperature_okay, 0);
        }

    }
}
#endif


#ifdef USE_BATTCHECK
#ifdef BATTCHECK_4bars
PROGMEM const uint8_t voltage_blinks[] = {
    30, 35, 38, 40, 42, 99,
};
#endif
#ifdef BATTCHECK_6bars
PROGMEM const uint8_t voltage_blinks[] = {
    30, 34, 36, 38, 40, 41, 43, 99,
};
#endif
#ifdef BATTCHECK_8bars
PROGMEM const uint8_t voltage_blinks[] = {
    30, 33, 35, 37, 38, 39, 40, 41, 42, 99,
};
#endif
void battcheck() {
    #ifdef BATTCHECK_VpT
    blink_num(voltage);
    #else
    uint8_t i;
    for(i=0;
        voltage >= pgm_read_byte(voltage_blinks + i);
        i++) {}
    #ifdef DONT_DELAY_AFTER_BATTCHECK
    blink_digit(i);
    #else
    if (blink_digit(i))
        nice_delay_ms(1000);
    #endif
    #endif
}
#endif

#endif