Powers off instead of sleeping

tama.c

@@ -37,6 +37,7 @@
 #define FRAME_MS        60      // main loop period
 #define TICK_FRAMES     250     // stat update every ~15 s (250 * 60 ms)
 #define ANIM_FRAMES     12      // how long an action reaction is shown
+#define TICK_MS  (TICK_FRAMES * FRAME_MS) // 15000 ms: also the screen-off check period
 
 // With the values below an untended pet survives roughly half an hour:
 // a need empties in ~20 min, after which health bleeds down over ~10 more.
@@ -87,14 +88,16 @@ static uint8_t  evo_anim;           // frames remaining for an evolution banner
 
 // settings
 static uint8_t  sound_on    = 1;
-static uint8_t  timeout_idx = 1; // index into screen_timeout_opts (default 30 s)
+static uint8_t  timeout_idx = 1; // index into screen_timeout_opts (default 10 s)
 static uint8_t  set_sel     = 0; // highlighted row on the settings screen
 static uint8_t  sel_species = 0; // highlighted species on the welcome screen
 
-// screen-off-on-inactivity options, in frames (0 = never sleep the display)
-static const uint16_t screen_timeout_opts[] = { 250, 500, 1000, 0 };
-static const char *const screen_timeout_names[] = { "15s", "30s", "60s", "Off" };
-#define TIMEOUT_OPT_COUNT 4
+// screen-off-on-inactivity options, in frames (0 = never sleep the display).
+// Shorter timeouts blank the OLED sooner, which is the single biggest power
+// win on a CR2032 — the panel draws far more than the dozing MCU.
+static const uint16_t screen_timeout_opts[] = { 83, 167, 250, 500, 1000, 0 };
+static const char *const screen_timeout_names[] = { "5s", "10s", "15s", "30s", "60s", "Off" };
+#define TIMEOUT_OPT_COUNT 6
 #define SETTINGS_ROWS     3      // screen-off, sound, back
 
 // display power state
@@ -571,6 +574,88 @@ static Buttons read_buttons(void)
 	return b;
 }
 
+// ----------------------------------------------------------------- low power
+// Two wake sources let the core idle in WFI light-sleep while the OLED is off:
+//   * a button press (EXTI falling edge) -> light the screen back up
+//   * a periodic TIM2 overflow (~once per game tick) -> run a quick check
+// WFI only gates the CPU clock, so SRAM/registers (and the whole Pet) survive
+// untouched; full standby would wipe them and force a reboot/splash on wake.
+static volatile uint8_t exti_wake;   // a button interrupt fired
+static volatile uint8_t tick_wake;   // the periodic check timer fired
+
+// OK=PC0->EXTI0, Right=PD5->EXTI5, Left=PD6->EXTI6 all share this vector.
+void EXTI7_0_IRQHandler(void) INTERRUPT_DECORATOR;
+void EXTI7_0_IRQHandler(void)
+{
+	EXTI->INTFR = EXTI_Line0 | EXTI_Line5 | EXTI_Line6;  // clear pending
+	exti_wake = 1;
+}
+
+void TIM2_IRQHandler(void) INTERRUPT_DECORATOR;
+void TIM2_IRQHandler(void)
+{
+	TIM2->INTFR = (uint16_t)~TIM_FLAG_Update;            // clear update flag
+	tick_wake = 1;
+}
+
+static void lowpower_setup(void)
+{
+	// --- button wake: falling-edge EXTI on the three button pins ---
+	// (AFIO + GPIO clocks were already enabled by funGpioInitAll.)
+	AFIO->EXTICR |= AFIO_EXTICR_EXTI0_PC |   // OK     on PC0
+	                AFIO_EXTICR_EXTI5_PD |   // Right  on PD5
+	                AFIO_EXTICR_EXTI6_PD;    // Left   on PD6
+	EXTI->INTENR |= EXTI_Line0 | EXTI_Line5 | EXTI_Line6;
+	EXTI->FTENR  |= EXTI_Line0 | EXTI_Line5 | EXTI_Line6;  // press == falling edge
+	NVIC_EnableIRQ(EXTI7_0_IRQn);
+
+	// --- periodic wake: TIM2 update IRQ, one overflow per game tick ---
+	RCC->APB1PCENR |= RCC_APB1Periph_TIM2;
+	TIM2->PSC    = 23999;                     // 24 MHz / 24000 = 1 kHz (1 ms/count)
+	TIM2->ATRLR  = TICK_MS - 1;               // overflow once per game tick
+	TIM2->SWEVGR = TIM_PSCReloadMode_Immediate; // latch PSC/ARR now
+	TIM2->INTFR  = (uint16_t)~TIM_FLAG_Update;
+	TIM2->DMAINTENR |= TIM_UIE;               // enable update interrupt
+	NVIC_EnableIRQ(TIM2_IRQn);
+	// the counter itself stays disabled until we actually enter low-power sleep
+}
+
+// Doze in WFI until a button or the periodic timer wakes us. Returns only once
+// the display has been switched back on (button press, or the pet dying while
+// we slept); otherwise it keeps running background ticks and sleeping again.
+static void enter_low_power(void)
+{
+	for (;;) {
+		exti_wake = 0;
+		tick_wake = 0;
+		TIM2->CNT   = 0;
+		TIM2->INTFR = (uint16_t)~TIM_FLAG_Update;
+		TIM2->CTLR1 |= TIM_CEN;               // arm the periodic wake
+		__WFI();                              // core clock gated until an IRQ
+		TIM2->CTLR1 &= ~TIM_CEN;              // halt it while we're awake
+
+		if (exti_wake) {                      // a button: bring the screen back
+			ssd1306_cmd(SSD1306_DISPLAYON);
+			disp_on     = 1;
+			idle_frames = 0;
+			tick_acc    = 0;
+			return;
+		}
+
+		// otherwise it was the periodic check: advance the pet a tick. This
+		// still chirps low-need reminders (and the death tune) over the buzzer.
+		if (pet.alive) {
+			game_tick();
+			if (!pet.alive) {                 // it died in its sleep: show the grave
+				ssd1306_cmd(SSD1306_DISPLAYON);
+				disp_on     = 1;
+				idle_frames = 0;
+				return;
+			}
+		}
+	}
+}
+
 // ----------------------------------------------------------------- setup
 static void gpio_setup(void)
 {
@@ -625,6 +710,7 @@ int main(void)
 {
 	SystemInit();
 	gpio_setup();
+	lowpower_setup();              // button-wake EXTI + periodic-check timer
 
 	Delay_Ms(120);                 // let the OLED rail settle
 	if (ssd1306_i2c_init()) {      // non-zero == failure
@@ -639,6 +725,16 @@ int main(void)
 	Buttons prev = {0, 0, 0};
 
 	while (1) {
+		if (!disp_on) {
+			// Display is off: hand the core to WFI light-sleep, waking only
+			// for button presses or the periodic background check. It returns
+			// once the screen is lit again; swallow whatever press woke us so
+			// it just wakes the display rather than also firing an action.
+			enter_low_power();
+			prev = read_buttons();
+			continue;
+		}
+
 		Buttons b = read_buttons();
 		uint8_t ok_edge    = b.ok    && !prev.ok;
 		uint8_t left_edge  = b.left  && !prev.left;
@@ -648,13 +744,7 @@ int main(void)
 
 		if (any_edge) idle_frames = 0;
 
-		if (!disp_on) {
-			// screen is asleep: the first press only wakes it (not an action)
-			if (any_edge) {
-				ssd1306_cmd(SSD1306_DISPLAYON);
-				disp_on = 1;
-			}
-		} else {
+		{
 			switch (screen) {
 			case SCR_SELECT:
 				if (left_edge) {