reworked nice_delay interrupt system and fixed some old issues:

- added set_state_deferred(), to avoid timing issues when changing state in loop()
  (fixes bug where first button press after version check was sometimes ignored,
   and similar issue after battcheck in simple UI)

- reduced chance of eating first button press after simple UI's battcheck,
  because it spent an extra second waiting after finishing the readout,
  and it wasn't intuitive for a single click to go from "post-battcheck darkness"
  to "off" during that period

- made interrupt_nice_delays() happen every time the state changes, instead of
  having nice_delay() explicitly check for state changes while it waits...
  (because the explicit check was buggy and used more ROM)

- made nice_delay_ms() abort immediately when interrupt is set, instead of waiting
  1ms before it even checks for the interrupt condition...  this makes aborted
  animations end a lot faster, with less visible flickering

- made blink_num() smaller and simpler, because changes listed above make it possible

- slightly changed order of events in main(), to accommodate for changes above

- fixed issue where battcheck would keep trying to blink out numbers while the user
  was holding 10H for voltage config mode

- ... and reduced ROM size by about 38 bytes

7 files changed, 38 insertions, 37 deletions

diff --git a/spaghetti-monster/anduril/anduril.c b/spaghetti-monster/anduril/anduril.c
index b497eb9..f5bf1ee 100644
--- a/spaghetti-monster/anduril/anduril.c
+++ b/spaghetti-monster/anduril/anduril.c
@@ -297,7 +297,8 @@ void loop() {
         // in simple mode, turn off after one readout
         // FIXME: can eat the next button press
         //        (state changes in loop() act weird)
-        if (simple_ui_active) set_state(off_state, 0);
+        if (simple_ui_active) set_state_deferred(off_state, 0);
+        else nice_delay_ms(1000);
         #endif
     }
     #endif
diff --git a/spaghetti-monster/anduril/version-check-mode.c b/spaghetti-monster/anduril/version-check-mode.c
index 76efde3..edb1723 100644
--- a/spaghetti-monster/anduril/version-check-mode.c
+++ b/spaghetti-monster/anduril/version-check-mode.c
@@ -39,7 +39,7 @@ inline void version_check_iter() {
     //while (button_is_pressed()) {}
     //empty_event_sequence();
 
-    set_state(off_state, 0);
+    set_state_deferred(off_state, 0);
 }
 
 
diff --git a/spaghetti-monster/fsm-events.c b/spaghetti-monster/fsm-events.c
index b4cb671..3279c14 100644
--- a/spaghetti-monster/fsm-events.c
+++ b/spaghetti-monster/fsm-events.c
@@ -126,7 +126,6 @@ inline void interrupt_nice_delays() { nice_delay_interrupt = 1; }
 //   0: state changed
 //   1: normal completion
 uint8_t nice_delay_ms(uint16_t ms) {
-    StatePtr old_state = current_state;
     /*  // delay_zero() implementation
     if (ms == 0) {
         CLKPR = 1<<CLKPCE; CLKPR = 0;  // full speed
@@ -135,6 +134,10 @@ uint8_t nice_delay_ms(uint16_t ms) {
     }
     */
     while(ms-- > 0) {
+        if (nice_delay_interrupt) {
+            return 0;
+        }
+
         #ifdef USE_DYNAMIC_UNDERCLOCKING
         #ifdef USE_RAMPING
         uint8_t level = actual_level;  // volatile, avoid repeat access
@@ -168,9 +171,6 @@ uint8_t nice_delay_ms(uint16_t ms) {
         // run pending system processes while we wait
         handle_deferred_interrupts();
 
-        if ((nice_delay_interrupt) || (old_state != current_state)) {
-            return 0;  // state changed; abort
-        }
         // handle events only afterward, so that any collapsed delays will
         // finish running the UI's loop() code before taking any further actions
         // (this helps make sure code runs in the correct order)
diff --git a/spaghetti-monster/fsm-main.c b/spaghetti-monster/fsm-main.c
index 790cc68..0457d75 100644
--- a/spaghetti-monster/fsm-main.c
+++ b/spaghetti-monster/fsm-main.c
@@ -139,6 +139,14 @@ int main() {
         // if event queue not empty, empty it
         process_emissions();
 
+        // if loop() tried to change state, process that now
+        StatePtr df = deferred_state;
+        if (df) {
+            set_state(df, deferred_state_arg);
+            deferred_state = NULL;
+            //deferred_state_arg = 0;  // unnecessary
+        }
+
         // enter standby mode if requested
         // (works better if deferred like this)
         if (go_to_standby) {
@@ -164,11 +172,12 @@ int main() {
         // catch up on interrupts
         handle_deferred_interrupts();
 
+        // turn delays back on, if they were off
+        nice_delay_interrupt = 0;
+
         // give the recipe some time slices
         loop();
 
-        // in case we fell through, turn delays back on
-        nice_delay_interrupt = 0;
     }
 }
 
diff --git a/spaghetti-monster/fsm-misc.c b/spaghetti-monster/fsm-misc.c
index 82be745..15cb659 100644
--- a/spaghetti-monster/fsm-misc.c
+++ b/spaghetti-monster/fsm-misc.c
@@ -83,13 +83,12 @@ uint8_t blink_big_num(uint16_t num) {
 #endif
 #ifdef USE_BLINK_NUM
 uint8_t blink_num(uint8_t num) {
-    //StatePtr old_state = current_state;
-    #if 0
+    #if 1
     uint8_t hundreds = num / 100;
     num = num % 100;
     uint8_t tens = num / 10;
     num = num % 10;
-    #else  // 8 bytes smaller
+    #else  // can be smaller or larger, depending on whether divmod is used elsewhere
     uint8_t hundreds = 0;
     uint8_t tens = 0;
     for(; num >= 100; hundreds ++, num -= 100);
@@ -102,32 +101,9 @@ uint8_t blink_num(uint8_t num) {
     nice_delay_ms(200);
     #endif
 
-    #if 0
-    if (hundreds) {
-        if (! blink_digit(hundreds)) return 0;
-        if (! blink_digit(tens)) return 0;
-    }
-    else if (tens) {
-        if (! blink_digit(tens)) return 0;
-    }
-    if (! blink_digit(num)) return 0;
-    return nice_delay_ms(1000);
-    #else // same size :(
-    if (hundreds) if (! blink_digit(hundreds)) return 0;
-    if (hundreds || tens) if (! blink_digit(tens)) return 0;
-    if (! blink_digit(num)) return 0;
-    return nice_delay_ms(1000);
-    #endif
-
-    /*
-    uint8_t volts, tenths;
-    volts = voltage / 10;
-    tenths = voltage % 10;
-    if (! blink(volts)) return;
-    nice_delay_ms(200);
-    if (! blink(tenths)) return;
-    nice_delay_ms(200);
-    */
+    if (hundreds) blink_digit(hundreds);
+    if (hundreds || tens) blink_digit(tens);
+    return blink_digit(num);
 }
 #endif
 
diff --git a/spaghetti-monster/fsm-states.c b/spaghetti-monster/fsm-states.c
index f91dc4b..4d9ac08 100644
--- a/spaghetti-monster/fsm-states.c
+++ b/spaghetti-monster/fsm-states.c
@@ -39,6 +39,9 @@ void _set_state(StatePtr new_state, uint16_t arg,
     current_state = new_state;
     // call new state-enter hook (don't use stack)
     if (new_state != NULL) current_state(enter_event, arg);
+
+    // since state changed, stop any animation in progress
+    interrupt_nice_delays();
 }
 
 int8_t push_state(StatePtr new_state, uint16_t arg) {
@@ -79,6 +82,11 @@ uint8_t set_state(StatePtr new_state, uint16_t arg) {
     return push_state(new_state, arg);
 }
 
+void set_state_deferred(StatePtr new_state, uint16_t arg) {
+    deferred_state = new_state;
+    deferred_state_arg = arg;
+}
+
 #ifndef DONT_USE_DEFAULT_STATE
 // bottom state on stack
 // handles default actions for LVP, thermal regulation, etc
diff --git a/spaghetti-monster/fsm-states.h b/spaghetti-monster/fsm-states.h
index 7d9361b..9964bc1 100644
--- a/spaghetti-monster/fsm-states.h
+++ b/spaghetti-monster/fsm-states.h
@@ -40,6 +40,13 @@ void _set_state(StatePtr new_state, uint16_t arg,
 int8_t push_state(StatePtr new_state, uint16_t arg);
 StatePtr pop_state();
 uint8_t set_state(StatePtr new_state, uint16_t arg);
+
+// if loop() needs to change state, use this instead of set_state()
+// (because this avoids race conditions)
+volatile StatePtr deferred_state;
+volatile uint16_t deferred_state_arg;
+void set_state_deferred(StatePtr new_state, uint16_t arg);
+
 #ifndef DONT_USE_DEFAULT_STATE
 uint8_t default_state(Event event, uint16_t arg);
 #endif