refactored how interrupts work...

  set a flag and return immediately,
  then handle the actual logic later during a less-critical code path
Enables smarter responses to standby wakeups.
Seems to fix missed button presses during standby,
  and most of the too-fast sleep ticks.
Also eliminated waits from button state measurement, so it can happen easier during standby.
  (also eliminates the chance of an infinite loop on extra-noisy hardware)
Also might improve timing-sensitive interrupts like attiny85 PWM channel 4,
  or a PWM-DSM hybrid technique I'd like to try.

BUT this change also appears to break the thermal sensor, so that needs to be fixed.

10 files changed, 108 insertions, 38 deletions

diff --git a/spaghetti-monster/fsm-adc.c b/spaghetti-monster/fsm-adc.c
index 6832e32..1fc5472 100644
--- a/spaghetti-monster/fsm-adc.c
+++ b/spaghetti-monster/fsm-adc.c
@@ -113,15 +113,44 @@ static inline uint8_t calc_voltage_divider(uint16_t value) {
 #else
 #define ADC_CYCLES_PER_SECOND 8
 #endif
-// TODO: is this better done in main() or WDT()?
+
+// save the measurement result, set a flag to show something happened,
+// and count how many times we've triggered since last counter reset
 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.
+    #if 0  // the fancy method is probably not even needed
+    // count up but wrap around from 255 to 128; not 255 to 0
+    // TODO: find a way to do this faster if possible
+    uint8_t val = irq_adc;  // cache volatile value
+    irq_adc = (val + 1) | (val & 0b10000000);
+    #else
+    irq_adc ++;
+    #endif
+    adc_value = ADC;  // save this for later use
+}
+
+void ADC_inner() {
+    // ignore the first measurement; the docs say it's junk
+    if (irq_adc < 2) {
+        ADC_start_measurement();  // start a second measurement
+        return;
+    }
+
+    // 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;
+
+    // if we're actually runnning, reset the status flags / counters
+    irq_adc = 0;
     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? 0/1 = battery voltage, 2/3 = temperature
     static uint8_t adc_step = 0;
 
     // LVP declarations
@@ -155,7 +184,7 @@ ISR(ADC_vect) {
     #define ADC_STEPS 2
     #endif
 
-    uint16_t measurement = ADC;  // latest 10-bit ADC reading
+    uint16_t measurement = adc_value;  // latest 10-bit ADC reading
 
     #ifdef USE_PSEUDO_RAND
     // real-world entropy makes this a true random, not pseudo
@@ -376,10 +405,6 @@ ISR(ADC_vect) {
         #endif
     #endif
 
-    #ifdef TICK_DURING_STANDBY
-        // if we were asleep, go back to sleep
-        if (go_to_standby) ADC_off();
-    #endif
 }
 
 #ifdef USE_BATTCHECK
diff --git a/spaghetti-monster/fsm-adc.h b/spaghetti-monster/fsm-adc.h
index 274fb4d..acb3da6 100644
--- a/spaghetti-monster/fsm-adc.h
+++ b/spaghetti-monster/fsm-adc.h
@@ -38,9 +38,15 @@
 #define VOLTAGE_FUDGE_FACTOR 5
 #endif
 #endif
+
+volatile uint8_t irq_adc = 0;  // ADC interrupt happened?
+uint16_t adc_value;  // last ADC measurement
+uint8_t adcint_enable = 0;  // is the current ADC result needed?
+void ADC_inner();  // do the actual ADC-related calculations
+
 volatile uint8_t voltage = 0;
-volatile uint8_t adcint_enable;  // kludge, because adc auto-retrigger won't turn off
 void low_voltage();
+
 #ifdef USE_BATTCHECK
 void battcheck();
 #ifdef BATTCHECK_VpT
diff --git a/spaghetti-monster/fsm-events.c b/spaghetti-monster/fsm-events.c
index 3e9a12d..e125e84 100644
--- a/spaghetti-monster/fsm-events.c
+++ b/spaghetti-monster/fsm-events.c
@@ -145,6 +145,9 @@ uint8_t nice_delay_ms(uint16_t ms) {
         _delay_loop_2(BOGOMIPS*98/100);
         #endif  // ifdef USE_DYNAMIC_UNDERCLOCKING
 
+        // run pending system processes while we wait
+        handle_deferred_interrupts();
+
         if ((nice_delay_interrupt) || (old_state != current_state)) {
             return 0;  // state changed; abort
         }
diff --git a/spaghetti-monster/fsm-main.c b/spaghetti-monster/fsm-main.c
index e537a9e..a898f41 100644
--- a/spaghetti-monster/fsm-main.c
+++ b/spaghetti-monster/fsm-main.c
@@ -160,6 +160,9 @@ int main() {
             standby_mode();
         }
 
+        // catch up on interrupts
+        handle_deferred_interrupts();
+
         // give the recipe some time slices
         loop();
 
@@ -168,4 +171,22 @@ int main() {
     }
 }
 
+
+void handle_deferred_interrupts() {
+    /*
+    if (irq_pcint) {  // button pressed or released
+        // nothing to do here
+        // (PCINT only matters during standby)
+    }
+    */
+    if (irq_adc) {  // ADC done measuring
+        ADC_inner();
+        // irq_adc = 0;  // takes care of itself
+    }
+    if (irq_wdt) {  // the clock ticked
+        WDT_inner();
+        // irq_wdt = 0;  // takes care of itself
+    }
+}
+
 #endif
diff --git a/spaghetti-monster/fsm-main.h b/spaghetti-monster/fsm-main.h
index cc469d7..55ae2ff 100644
--- a/spaghetti-monster/fsm-main.h
+++ b/spaghetti-monster/fsm-main.h
@@ -21,5 +21,7 @@
 #define FSM_MAIN_H
 
 int main();
+// needs to run frequently to execute the logic for WDT and ADC and stuff
+void handle_deferred_interrupts();
 
 #endif
diff --git a/spaghetti-monster/fsm-pcint.c b/spaghetti-monster/fsm-pcint.c
index 4928980..a4a496a 100644
--- a/spaghetti-monster/fsm-pcint.c
+++ b/spaghetti-monster/fsm-pcint.c
@@ -24,19 +24,9 @@
 #include <util/delay_basic.h>
 
 uint8_t button_is_pressed() {
-    // remember the past 32 measurements
-    static uint32_t readings = 0;
-    // take at least one new measurement,
-    // and wait for measurements to settle to all zeroes or all ones
-    do {
-        // shift past readings and add current value
-        readings = (readings << 1) | ((SWITCH_PORT & (1<<SWITCH_PIN)) == 0);
-        // wait a moment
-        _delay_loop_2(BOGOMIPS/16);  // up to 2ms to stabilize
-    }
-    while ((readings != 0) && (readings != 0xFFFFFFFF));
-    button_last_state = readings;
-    return readings;
+    uint8_t value = ((SWITCH_PORT & (1<<SWITCH_PIN)) == 0);
+    button_last_state = value;
+    return value;
 }
 
 inline void PCINT_on() {
@@ -75,7 +65,10 @@ inline void PCINT_off() {
 
 //void button_change_interrupt() {
 #if (ATTINY == 25) || (ATTINY == 45) || (ATTINY == 85) || (ATTINY == 1634)
-EMPTY_INTERRUPT(PCINT0_vect);
+//EMPTY_INTERRUPT(PCINT0_vect);
+ISR(PCINT0_vect) {
+    irq_pcint = 1;
+}
 #else
     #error Unrecognized MCU type
 #endif
diff --git a/spaghetti-monster/fsm-pcint.h b/spaghetti-monster/fsm-pcint.h
index ec3ae4b..a7f3733 100644
--- a/spaghetti-monster/fsm-pcint.h
+++ b/spaghetti-monster/fsm-pcint.h
@@ -20,6 +20,7 @@
 #ifndef FSM_PCINT_H
 #define FSM_PCINT_H
 
+volatile uint8_t irq_pcint = 0;  // pin change interrupt happened?
 //static volatile uint8_t button_was_pressed;
 #define BP_SAMPLES 32
 volatile uint8_t button_last_state;
diff --git a/spaghetti-monster/fsm-standby.c b/spaghetti-monster/fsm-standby.c
index 44b047a..4124d92 100644
--- a/spaghetti-monster/fsm-standby.c
+++ b/spaghetti-monster/fsm-standby.c
@@ -42,13 +42,15 @@ void sleep_until_eswitch_pressed()
     // make sure switch isn't currently pressed
     while (button_is_pressed()) {}
     empty_event_sequence();  // cancel pending input on suspend
-    //PCINT_since_WDT = 0;  // ensure PCINT won't ignore itself
 
     PCINT_on();  // wake on e-switch event
 
     #ifdef TICK_DURING_STANDBY
+    // detect which type of event caused a wake-up
+    irq_adc = 0;
+    irq_wdt = 0;
+    irq_pcint = 0;
     while (go_to_standby) {
-        f_wdt = 0;  // detect if WDT was what caused a wake-up
     #else
         go_to_standby = 0;
     #endif
@@ -65,10 +67,19 @@ void sleep_until_eswitch_pressed()
         sleep_disable();
 
     #ifdef TICK_DURING_STANDBY
-        // determine what woke us up... WDT or PCINT
-        if (! f_wdt) {  // PCINT went off; wake up
+        // determine what woke us up...
+        if (irq_pcint) {  // button pressed; wake up
             go_to_standby = 0;
         }
+        if (irq_adc) {  // ADC done measuring
+            adcint_enable = 1;
+            ADC_inner();
+            //ADC_off();  // takes care of itself
+            //irq_adc = 0;  // takes care of itself
+        }
+        if (irq_wdt) {  // generate a sleep tick
+            WDT_inner();
+        }
     }
     #endif
 
diff --git a/spaghetti-monster/fsm-wdt.c b/spaghetti-monster/fsm-wdt.c
index 6e61e87..3cb7d86 100644
--- a/spaghetti-monster/fsm-wdt.c
+++ b/spaghetti-monster/fsm-wdt.c
@@ -82,11 +82,23 @@ inline void WDT_off()
 
 // clock tick -- this runs every 16ms (62.5 fps)
 ISR(WDT_vect) {
+    irq_wdt = 1;  // WDT event happened
+}
+
+void WDT_inner() {
+    irq_wdt = 0;  // WDT event handled; reset flag
+
     static uint8_t adc_trigger = 0;
 
-    #ifdef TICK_DURING_STANDBY
-    f_wdt = 1;  // WDT event happened
+    // detect and emit button change events (even during standby)
+    uint8_t was_pressed = button_last_state;
+    uint8_t pressed = button_is_pressed();
+    if (was_pressed != pressed) {
+        go_to_standby = 0;
+        PCINT_inner(pressed);
+    }
 
+    #ifdef TICK_DURING_STANDBY
     static uint16_t sleep_counter = 0;
     // handle standby mode specially
     if (go_to_standby) {
@@ -107,11 +119,6 @@ ISR(WDT_vect) {
     else { sleep_counter = 0; }
     #endif
 
-    // detect and emit button change events
-    uint8_t was_pressed = button_last_state;
-    uint8_t pressed = button_is_pressed();
-    if (was_pressed != pressed) PCINT_inner(pressed);
-
     // cache this here to reduce ROM size, because it's volatile
     uint16_t ticks_since_last = ticks_since_last_event;
  
@@ -178,6 +185,7 @@ ISR(WDT_vect) {
         if (go_to_standby) ADC_on();
         #endif
         ADC_start_measurement();
+        irq_adc = 0;
         adcint_enable = 1;
     }
     #endif
diff --git a/spaghetti-monster/fsm-wdt.h b/spaghetti-monster/fsm-wdt.h
index 78fe791..d127551 100644
--- a/spaghetti-monster/fsm-wdt.h
+++ b/spaghetti-monster/fsm-wdt.h
@@ -25,9 +25,9 @@
 void WDT_on();
 inline void WDT_off();
 
-#ifdef TICK_DURING_STANDBY
-volatile uint8_t f_wdt = 0;
+volatile uint8_t irq_wdt = 0;  // WDT interrupt happened?
 
+#ifdef TICK_DURING_STANDBY
   #if defined(USE_INDICATOR_LED) || defined(USE_AUX_RGB_LEDS)
   // measure battery charge while asleep
   #define USE_SLEEP_LVP