Debouncing finally works (at least, it does on my two test hosts).

4 files changed, 25 insertions, 56 deletions

diff --git a/spaghetti-monster/fsm-pcint.c b/spaghetti-monster/fsm-pcint.c
index c04375a..722cb88 100644
--- a/spaghetti-monster/fsm-pcint.c
+++ b/spaghetti-monster/fsm-pcint.c
@@ -24,20 +24,19 @@
 #include <util/delay_basic.h>
 
 uint8_t button_is_pressed() {
-    // debounce a little
-    uint8_t highcount = 0;
-    // measure for 16/64ths of a ms
-    for(uint8_t i=0; i<BP_SAMPLES; i++) {
-        // check current value
-        uint8_t bit = ((PINB & (1<<SWITCH_PIN)) == 0);
-        highcount += bit;
+    // 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) | ((PINB & (1<<SWITCH_PIN)) == 0);
         // wait a moment
-        _delay_loop_2(BOGOMIPS/64);
+        _delay_loop_2(BOGOMIPS/16);  // up to 2ms to stabilize
     }
-    // use most common value
-    uint8_t result = (highcount > (BP_SAMPLES/2));
-    //button_was_pressed = result;
-    return result;
+    while ((readings != 0) && (readings != 0xFFFFFFFF));
+    button_last_state = readings;
+    return readings;
 }
 
 inline void PCINT_on() {
@@ -59,20 +58,15 @@ ISR(PCINT0_vect) {
 
     //DEBUG_FLASH;
 
-    /*
-    uint8_t pressed;
+    // as it turns out, it's more reliable to detect pin changes from WDT
+    // because PCINT itself tends to double-tap when connected to a
+    // noisy / bouncy switch (so the content of this function has been
+    // moved to a separate function, called from WDT only)
+    // PCINT_inner(button_is_pressed());
 
-    // add event to current sequence
-    pressed = button_is_pressed();
-    PCINT_inner(pressed);
-    */
-    if (! PCINT_since_WDT) {
-        PCINT_since_WDT = 1;
-        PCINT_inner(button_is_pressed());
-    }
 }
 
-// should only be called from PCINT and WDT
+// should only be called from PCINT and/or WDT
 // (is a separate function to reduce code duplication)
 void PCINT_inner(uint8_t pressed) {
     uint8_t pushed;
diff --git a/spaghetti-monster/fsm-pcint.h b/spaghetti-monster/fsm-pcint.h
index a94fc82..ec3ae4b 100644
--- a/spaghetti-monster/fsm-pcint.h
+++ b/spaghetti-monster/fsm-pcint.h
@@ -23,7 +23,6 @@
 //static volatile uint8_t button_was_pressed;
 #define BP_SAMPLES 32
 volatile uint8_t button_last_state;
-volatile uint8_t PCINT_since_WDT;
 uint8_t button_is_pressed();
 inline void PCINT_on();
 inline void PCINT_off();
diff --git a/spaghetti-monster/fsm-standby.c b/spaghetti-monster/fsm-standby.c
index eb631d6..b90ccea 100644
--- a/spaghetti-monster/fsm-standby.c
+++ b/spaghetti-monster/fsm-standby.c
@@ -37,7 +37,7 @@ 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_since_WDT = 0;  // ensure PCINT won't ignore itself
 
     PCINT_on();  // wake on e-switch event
 
diff --git a/spaghetti-monster/fsm-wdt.c b/spaghetti-monster/fsm-wdt.c
index bee2914..777bef0 100644
--- a/spaghetti-monster/fsm-wdt.c
+++ b/spaghetti-monster/fsm-wdt.c
@@ -45,47 +45,23 @@ inline void WDT_off()
 
 // clock tick -- this runs every 16ms (62.5 fps)
 ISR(WDT_vect) {
+    // 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);
+
     //if (ticks_since_last_event < 0xff) ticks_since_last_event ++;
     // increment, but loop from max back to half
     ticks_since_last_event = (ticks_since_last_event + 1) \
                              | (ticks_since_last_event & 0x8000);
 
-    // just in case the pin change interrupt missed something
-    uint8_t le_num = last_event_num();
-    uint8_t last_event = 0;
-    if (le_num >= 1) last_event = current_event[le_num-1];
-    uint8_t pressed = button_is_pressed();
-    uint8_t was_pressed_before = (last_event == A_PRESS) || (last_event == A_HOLD);
-    //if (pressed != button_last_state) {
-    if (pressed != was_pressed_before) {
-        PCINT_inner(pressed);
-        /*
-        uint8_t pushed;
-        if (pressed) {
-            pushed = push_event(A_PRESS);
-        } else {
-            pushed = push_event(A_RELEASE);
-        }
-
-        // check if sequence matches any defined sequences
-        // if so, send event to current state callback
-        if (pushed) {
-            button_last_state = pressed;
-            emit_current_event(0);
-        }
-        */
-    }
-    PCINT_since_WDT = 0;
-
     // if time since last event exceeds timeout,
     // append timeout to current event sequence, then
     // send event to current state callback
 
     // preload recent events
-    //uint8_t le_num = last_event_num();
-    le_num = last_event_num();
-    //uint8_t last_event = 0;
-    last_event = 0;
+    uint8_t le_num = last_event_num();
+    uint8_t last_event = 0;
     uint8_t prev_event = 0;
     if (le_num >= 1) last_event = current_event[le_num-1];
     if (le_num >= 2) prev_event = current_event[le_num-2];