merged irq-refactor branch, which fixes some small but long-standing issues:

- fixed occasional short/aborted frames in aux LED sleep animation
- fixed rare case of bogus voltage and/or temperature values
- fixed issue where nice_delay_ms() didn't work in setup()
- fixed theoretical possibility of extra-noisy buttons causing a hang
- fixed reboot loop which happened after any crashes
- fixed issue where button press in sleep mode could occasionally crash
  (but the issue may have been created by this branch before being fixed by it)
- reduced occasional missed button events while asleep
  (still seems to happen but not nearly as much)

Also does some other things:
- cleans up the ADC code significantly
- cleans up the WDT code
- adds a voltage stabilizer/lowpass option (enabled on t1634 builds)
- greatly reduces time spent per interrupt,
  which might make a future PWM-DSM technique possible
- moves most interrupt-handling logic to a non-critical code path,
  deferring that code until timing doesn't matter as much
- sped up button state measurements
- very slightly reduces power used in sleep mode

1 files changed, 249 insertions, 229 deletions

diff --git a/spaghetti-monster/fsm-adc.c b/spaghetti-monster/fsm-adc.c
index 6832e32..4ee2018 100644
--- a/spaghetti-monster/fsm-adc.c
+++ b/spaghetti-monster/fsm-adc.c
@@ -21,7 +21,7 @@
 #define FSM_ADC_C
 
 
-inline void set_admux_therm() {
+static inline void set_admux_therm() {
     #if (ATTINY == 25) || (ATTINY == 45) || (ATTINY == 85) || (ATTINY == 1634)
         ADMUX = ADMUX_THERM;
     #elif (ATTINY == 841)
@@ -30,6 +30,7 @@ inline void set_admux_therm() {
     #else
         #error Unrecognized MCU type
     #endif
+    adc_channel = 1;
 }
 
 inline void set_admux_voltage() {
@@ -52,6 +53,7 @@ inline void set_admux_voltage() {
     #else
         #error Unrecognized MCU type
     #endif
+    adc_channel = 0;
 }
 
 inline void ADC_start_measurement() {
@@ -106,43 +108,165 @@ static inline uint8_t calc_voltage_divider(uint16_t value) {
 }
 #endif
 
-// Each full cycle runs 7.8X per second with just voltage enabled,
-// or 3.9X per second with voltage and temperature.
+// Each full cycle runs 15.6X per second with just voltage enabled,
+// or 7.8X per second with voltage and temperature.
 #if defined(USE_LVP) && defined(USE_THERMAL_REGULATION)
-#define ADC_CYCLES_PER_SECOND 4
-#else
 #define ADC_CYCLES_PER_SECOND 8
+#else
+#define ADC_CYCLES_PER_SECOND 16
+#endif
+
+#ifdef USE_THERMAL_REGULATION
+#define ADC_STEPS 2
+#else
+#define ADC_STEPS 1
 #endif
-// TODO: is this better done in main() or WDT()?
+
+// happens every time the ADC sampler finishes a measurement
 ISR(ADC_vect) {
-    // For some reason, the ADC interrupt is getting called a *lot*
-    // more often than it should be, like it's auto-triggering after each
-    // measurement, but I don't know why, or how to turn that off...
-    // So, skip every call except when explicitly requested.
+    #ifdef USE_PSEUDO_RAND
+    // real-world entropy makes this a true random, not pseudo
+    pseudo_rand_seed += ADCL;
+    #endif
+
+    if (irq_adc_stable) {  // skip first result; it's junk
+        adc_values[adc_channel] = ADC;  // save this for later use
+        irq_adc = 1;  // a value was saved, so trigger deferred logic
+    }
+    irq_adc_stable = 1;
+
+    // start another measurement
+    // (is explicit because it otherwise doesn't seem to happen during standby mode)
+    ADC_start_measurement();
+}
+
+void ADC_inner() {
+    irq_adc = 0;  // event handled
+
+    // the ADC triggers repeatedly when it's on, but we only want one value
+    // (so ignore everything after the first value, until it's manually reset)
     if (! adcint_enable) return;
+
+    // disable after one iteration
     adcint_enable = 0;
 
+    #ifdef TICK_DURING_STANDBY
+        // 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();
+    #endif
+
+    // what is being measured? 0 = battery voltage, 1 = temperature
     static uint8_t adc_step = 0;
 
-    // LVP declarations
     #ifdef USE_LVP
-    #ifdef USE_LVP_AVG
-    #define NUM_VOLTAGE_VALUES 4
-    static int16_t voltage_values[NUM_VOLTAGE_VALUES];
+    if (0 == adc_step) {  // voltage
+        ADC_voltage_handler();
+    }
     #endif
+
+    #ifdef USE_THERMAL_REGULATION
+    else if (1 == adc_step) {  // temperature
+        ADC_temperature_handler();
+    }
+    #endif
+
+    #if defined(TICK_DURING_STANDBY) && defined(USE_SLEEP_LVP)
+    // only measure battery voltage while asleep
+    if (go_to_standby) adc_step = 0;
+    else
+    #endif
+
+    adc_step = (adc_step + 1) & (ADC_STEPS-1);
+
+    // set the correct type of measurement for next time
+    #ifdef USE_THERMAL_REGULATION
+        #ifdef USE_LVP
+        if (0 == adc_step) set_admux_voltage();
+        else set_admux_therm();
+        #else
+        //set_admux_therm();
+        #error "USE_THERMAL_REGULATION set without USE_LVP"
+        #endif
+    #else
+        #ifdef USE_LVP
+        set_admux_voltage();
+        #endif
+    #endif
+
+    irq_adc_stable = 0;  // first result is unstable
+}
+
+
+#ifdef USE_LVP
+static inline void ADC_voltage_handler() {
     static uint8_t lvp_timer = 0;
     static uint8_t lvp_lowpass = 0;
     #define LVP_TIMER_START (VOLTAGE_WARNING_SECONDS*ADC_CYCLES_PER_SECOND)  // N seconds between LVP warnings
     #define LVP_LOWPASS_STRENGTH ADC_CYCLES_PER_SECOND  // lowpass for one second
+
+    uint16_t measurement = adc_values[0];  // latest 10-bit ADC reading
+
+    #ifdef USE_VOLTAGE_LOWPASS
+        static uint16_t prev_measurement = 0;
+
+        // prime on first execution, or while asleep
+        if (go_to_standby || (! prev_measurement)) prev_measurement = measurement;
+
+        // only allow raw value to go up or down by 1 per iteration
+        if (measurement > prev_measurement) measurement = prev_measurement + 1;
+        else if (measurement < prev_measurement) measurement = prev_measurement - 1;
+
+        // remember for later
+        prev_measurement = measurement;
+    #endif  // no USE_VOLTAGE_LOWPASS
+
+    #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)(1.1*1024*10)/measurement + VOLTAGE_FUDGE_FACTOR;
+    voltage = ((uint16_t)(2*1.1*1024*10)/measurement + VOLTAGE_FUDGE_FACTOR) >> 1;
     #endif
 
+    // if low, callback EV_voltage_low / EV_voltage_critical
+    //         (but only if it has been more than N ticks since last call)
+    if (lvp_timer) {
+        lvp_timer --;
+    } else {  // it has been long enough since the last warning
+        if (voltage < VOLTAGE_LOW) {
+            if (lvp_lowpass < LVP_LOWPASS_STRENGTH) {
+                lvp_lowpass ++;
+            } else {
+                // try to send out a warning
+                //uint8_t err = emit(EV_voltage_low, 0);
+                //uint8_t err = emit_now(EV_voltage_low, 0);
+                emit(EV_voltage_low, 0);
+                //if (!err) {
+                    // on successful warning, reset counters
+                    lvp_timer = LVP_TIMER_START;
+                    lvp_lowpass = 0;
+                //}
+            }
+        } else {
+            // voltage not low?  reset count
+            lvp_lowpass = 0;
+        }
+    }
+}
+#endif
+
+
+#ifdef USE_THERMAL_REGULATION
+static inline void ADC_temperature_handler() {
     // thermal declarations
-    #ifdef USE_THERMAL_REGULATION
     #ifndef THERMAL_UPDATE_SPEED
     #define THERMAL_UPDATE_SPEED 2
     #endif
     #define NUM_THERMAL_VALUES_HISTORY 8
-    #define ADC_STEPS 4
     static uint8_t history_step = 0;  // don't update history as often
     static int16_t temperature_history[NUM_THERMAL_VALUES_HISTORY];
     static uint8_t temperature_timer = 0;
@@ -151,236 +275,132 @@ ISR(ADC_vect) {
     #define TEMPERATURE_TIMER_START ((THERMAL_WARNING_SECONDS-2)*ADC_CYCLES_PER_SECOND)  // N seconds between thermal regulation events
     #define OVERHEAT_LOWPASS_STRENGTH (ADC_CYCLES_PER_SECOND*2)  // lowpass for 2 seconds
     #define UNDERHEAT_LOWPASS_STRENGTH (ADC_CYCLES_PER_SECOND*2)  // lowpass for 2 seconds
-    #else
-    #define ADC_STEPS 2
-    #endif
-
-    uint16_t measurement = ADC;  // latest 10-bit ADC reading
-
-    #ifdef USE_PSEUDO_RAND
-    // real-world entropy makes this a true random, not pseudo
-    pseudo_rand_seed += measurement;
-    #endif
-
-    #if defined(TICK_DURING_STANDBY) && defined(USE_SLEEP_LVP)
-    // only measure battery voltage while asleep
-    if (go_to_standby) adc_step = 1;
-    else
-    #endif
-
-    adc_step = (adc_step + 1) & (ADC_STEPS-1);
 
-    #ifdef USE_LVP
-    // voltage
-    if (adc_step == 1) {
-        #ifdef USE_LVP_AVG
-        // prime on first execution
-        if (voltage == 0) {
-            for(uint8_t i=0; i<NUM_VOLTAGE_VALUES; i++)
-                voltage_values[i] = measurement;
-            voltage = 42;  // the answer to life, the universe, and the voltage of a full li-ion cell
-        } else {
-            uint16_t total = 0;
-            uint8_t i;
-            for(i=0; i<NUM_VOLTAGE_VALUES-1; i++) {
-                voltage_values[i] = voltage_values[i+1];
-                total += voltage_values[i];
-            }
-            voltage_values[i] = measurement;
-            total += measurement;
-            total = total >> 2;
-
-            #ifdef USE_VOLTAGE_DIVIDER
-            voltage = calc_voltage_divider(total);
-            #else
-            voltage = (uint16_t)(1.1*1024*10)/total + VOLTAGE_FUDGE_FACTOR;
-            #endif
-        }
-        #else  // no USE_LVP_AVG
-            #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)(1.1*1024*10)/measurement + VOLTAGE_FUDGE_FACTOR;
-            voltage = ((uint16_t)(2*1.1*1024*10)/measurement + VOLTAGE_FUDGE_FACTOR) >> 1;
-            #endif
-        #endif
-        // if low, callback EV_voltage_low / EV_voltage_critical
-        //         (but only if it has been more than N ticks since last call)
-        if (lvp_timer) {
-            lvp_timer --;
-        } else {  // it has been long enough since the last warning
-            if (voltage < VOLTAGE_LOW) {
-                if (lvp_lowpass < LVP_LOWPASS_STRENGTH) {
-                    lvp_lowpass ++;
-                } else {
-                    // try to send out a warning
-                    //uint8_t err = emit(EV_voltage_low, 0);
-                    //uint8_t err = emit_now(EV_voltage_low, 0);
-                    emit(EV_voltage_low, 0);
-                    //if (!err) {
-                        // on successful warning, reset counters
-                        lvp_timer = LVP_TIMER_START;
-                        lvp_lowpass = 0;
-                    //}
-                }
-            } else {
-                // voltage not low?  reset count
-                lvp_lowpass = 0;
-            }
+    uint16_t measurement = adc_values[1];  // latest 10-bit ADC reading
+
+    // Convert ADC units to Celsius (ish)
+    int16_t temp = measurement - 275 + THERM_CAL_OFFSET + (int16_t)therm_cal_offset;
+
+    // prime on first execution
+    if (reset_thermal_history) {
+        reset_thermal_history = 0;
+        temperature = temp;
+        for(uint8_t i=0; i<NUM_THERMAL_VALUES_HISTORY; i++)
+            temperature_history[i] = temp;
+    } else {  // update our current temperature estimate
+        // crude lowpass filter
+        // (limit rate of change to 1 degree per measurement)
+        if (temp > temperature) {
+            temperature ++;
+        } else if (temp < temperature) {
+            temperature --;
         }
     }
-    #endif  // ifdef USE_LVP
 
+    // guess what the temperature will be in a few seconds
+    int16_t pt;
+    {
+        int16_t diff;
+        int16_t t = temperature;
 
-    #ifdef USE_THERMAL_REGULATION
-    // temperature
-    else if (adc_step == 3) {
-        // Convert ADC units to Celsius (ish)
-        int16_t temp = measurement - 275 + THERM_CAL_OFFSET + (int16_t)therm_cal_offset;
-
-        // prime on first execution
-        if (reset_thermal_history) {
-            reset_thermal_history = 0;
-            temperature = temp;
-            for(uint8_t i=0; i<NUM_THERMAL_VALUES_HISTORY; i++)
-                temperature_history[i] = temp;
-        } else {  // update our current temperature estimate
-            // crude lowpass filter
-            // (limit rate of change to 1 degree per measurement)
-            if (temp > temperature) {
-                temperature ++;
-            } else if (temp < temperature) {
-                temperature --;
+        // 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 5
+        // highest temperature allowed
+        #define THERM_CEIL ((int16_t)therm_ceil)
+        // bottom of target temperature window
+        #define THERM_FLOOR (THERM_CEIL - THERM_WINDOW_SIZE)
+
+        // if it's time to rotate the thermal history, do it
+        history_step ++;
+        #if (THERMAL_UPDATE_SPEED == 4)  // new value every 4s
+        #define THERM_HISTORY_STEP_MAX ((2*ADC_CYCLES_PER_SECOND)-1)
+        #elif (THERMAL_UPDATE_SPEED == 2)  // new value every 2s
+        #define THERM_HISTORY_STEP_MAX (ADC_CYCLES_PER_SECOND-1)
+        #elif (THERMAL_UPDATE_SPEED == 1)  // new value every 1s
+        #define THERM_HISTORY_STEP_MAX ((ADC_CYCLES_PER_SECOND/2)-1)
+        #elif (THERMAL_UPDATE_SPEED == 0)  // new value every 0.5s
+        #define THERM_HISTORY_STEP_MAX ((ADC_CYCLES_PER_SECOND/4)-1)
+        #endif
+        if (0 == (history_step & THERM_HISTORY_STEP_MAX)) {
+            // 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] = t;
         }
 
-        // guess what the temperature will be in a few seconds
-        int16_t pt;
-        {
-            int16_t diff;
-            int16_t t = temperature;
-
-            // 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 5
-            // highest temperature allowed
-            #define THERM_CEIL ((int16_t)therm_ceil)
-            // bottom of target temperature window
-            #define THERM_FLOOR (THERM_CEIL - THERM_WINDOW_SIZE)
-
-            // if it's time to rotate the thermal history, do it
-            history_step ++;
-            #if (THERMAL_UPDATE_SPEED == 4)  // new value every 4s
-            #define THERM_HISTORY_STEP_MAX 15
-            #elif (THERMAL_UPDATE_SPEED == 2)  // new value every 2s
-            #define THERM_HISTORY_STEP_MAX 7
-            #elif (THERMAL_UPDATE_SPEED == 1)  // new value every 1s
-            #define THERM_HISTORY_STEP_MAX 3
-            #elif (THERMAL_UPDATE_SPEED == 0)  // new value every 0.5s
-            #define THERM_HISTORY_STEP_MAX 1
-            #endif
-            if (0 == (history_step & THERM_HISTORY_STEP_MAX)) {
-                // 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] = t;
-            }
-
-            // guess what the temp will be several seconds in the future
-            // diff = rate of temperature change
-            //diff = temperature_history[NUM_THERMAL_VALUES_HISTORY-1] - temperature_history[0];
-            diff = t - temperature_history[0];
-            // slight bias toward zero; ignore very small changes (noise)
-            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
-            //projected_temperature = temperature_history[NUM_THERMAL_VALUES_HISTORY-1] + (diff<<THERM_PREDICTION_STRENGTH);
-            pt = projected_temperature = t + (diff<<THERM_PREDICTION_STRENGTH);
+        // guess what the temp will be several seconds in the future
+        // diff = rate of temperature change
+        //diff = temperature_history[NUM_THERMAL_VALUES_HISTORY-1] - temperature_history[0];
+        diff = t - temperature_history[0];
+        // slight bias toward zero; ignore very small changes (noise)
+        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
+        //projected_temperature = temperature_history[NUM_THERMAL_VALUES_HISTORY-1] + (diff<<THERM_PREDICTION_STRENGTH);
+        pt = projected_temperature = t + (diff<<THERM_PREDICTION_STRENGTH);
+    }
 
-        // cancel counters if appropriate
-        if (pt > THERM_FLOOR) {
-            underheat_lowpass = 0;  // we're probably not too cold
-        }
-        if (pt < THERM_CEIL) {
-            overheat_lowpass = 0;  // we're probably not too hot
-        }
+    // cancel counters if appropriate
+    if (pt > THERM_FLOOR) {
+        underheat_lowpass = 0;  // we're probably not too cold
+    }
+    if (pt < THERM_CEIL) {
+        overheat_lowpass = 0;  // we're probably not too hot
+    }
+
+    if (temperature_timer) {
+        temperature_timer --;
+    } else {  // it has been long enough since the last warning
 
-        if (temperature_timer) {
-            temperature_timer --;
-        } else {  // it has been long enough since the last warning
-
-            // Too hot?
-            if (pt > THERM_CEIL) {
-                if (overheat_lowpass < OVERHEAT_LOWPASS_STRENGTH) {
-                    overheat_lowpass ++;
-                } else {
-                    // reset counters
-                    overheat_lowpass = 0;
-                    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;
-                    // try to send out a warning
-                    emit(EV_temperature_high, howmuch);
-                }
+        // Too hot?
+        if (pt > THERM_CEIL) {
+            if (overheat_lowpass < OVERHEAT_LOWPASS_STRENGTH) {
+                overheat_lowpass ++;
+            } else {
+                // reset counters
+                overheat_lowpass = 0;
+                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;
+                // try to send out a warning
+                emit(EV_temperature_high, howmuch);
             }
+        }
 
-            // Too cold?
-            else if (pt < THERM_FLOOR) {
-                if (underheat_lowpass < UNDERHEAT_LOWPASS_STRENGTH) {
-                    underheat_lowpass ++;
-                } else {
-                    // reset counters
-                    underheat_lowpass = 0;
-                    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;
-                    // try to send out a warning (unless voltage is low)
-                    // (LVP and underheat warnings fight each other)
-                    if (voltage > VOLTAGE_LOW)
-                        emit(EV_temperature_low, howmuch);
-                }
+        // Too cold?
+        else if (pt < THERM_FLOOR) {
+            if (underheat_lowpass < UNDERHEAT_LOWPASS_STRENGTH) {
+                underheat_lowpass ++;
+            } else {
+                // reset counters
+                underheat_lowpass = 0;
+                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;
+                // try to send out a warning (unless voltage is low)
+                // (LVP and underheat warnings fight each other)
+                if (voltage > VOLTAGE_LOW)
+                    emit(EV_temperature_low, howmuch);
             }
         }
     }
-    #endif  // ifdef USE_THERMAL_REGULATION
-
-
-    // set the correct type of measurement for next time
-    #ifdef USE_THERMAL_REGULATION
-        #ifdef USE_LVP
-        if (adc_step < 2) set_admux_voltage();
-        else set_admux_therm();
-        #else
-        set_admux_therm();
-        #endif
-    #else
-        #ifdef USE_LVP
-        set_admux_voltage();
-        #endif
-    #endif
-
-    #ifdef TICK_DURING_STANDBY
-        // if we were asleep, go back to sleep
-        if (go_to_standby) ADC_off();
-    #endif
 }
+#endif
+
 
 #ifdef USE_BATTCHECK
 #ifdef BATTCHECK_4bars