Merge pull request 'Disable unused peripherals for power saving' (#5) from feature/energy-saving into main

Reviewed-on: #5

main.c

@@ -1,6 +1,7 @@
 /**
  * @file main.c
- * @brief Bike rear light implementation for ATTINY202 with low-power standby.
+ * @brief Bike rear light implementation for ATTINY202.
+ *
  */
 
 #include <stdint.h>
@@ -17,13 +18,16 @@
 #define PA6_SET_MASK 0x40    ///< Green LED pin
 #define PA7_SET_MASK 0x80    ///< Red LED
 
-#define MAIN_LOOP_SLEEP 50U                 // Loop period in ms
+#define MAIN_LOOP_SLEEP 10U                 // Main loop delay in ms
 #define BUTTON_LONG_PRESS_DURATION_MS 1000U // Long press threshold
 #define BUTTON_SHORT_PRESS_DURATION_MS 50U  // Short press threshold
 #define BUTTON_IGNORE_DURATION_MS 2000U     // Time button ignored after long press
 #define BUTTON_CONFIRMATION_BLINK_LOOPS 10U // Blink animation for confirmation
 #define BUTTON_CONFIRMATION_BLINK_DURATION_MS 50U
+#define GLOW_BRIGHTNESS_MIN 10U
+#define GLOW_BRIGHTNESS_MAX 100U
 
+/** Convert milliseconds to system ticks */
 #define MS_TO_TICKS(ms) ((ms) / MAIN_LOOP_SLEEP)
 
 typedef enum _Mode
@@ -42,6 +46,7 @@ volatile eMode eModeCurrent = ANIMATION_BLINK;
 // Forward declarations
 ISR(PORTA_PORT_vect);
 static void software_reset(void);
+static void configureLowPower(void);
 void initPWM(void);
 void setPWM_PA2(uint8_t duty);
 static inline void leds_off(void);
@@ -53,27 +58,15 @@ void ledAnimationBlink(bool resetCounters);
 void ledAnimationGlow(void);
 void ledStaticFull(void);
 
-/* --- Timer init: Use RTC PIT for periodic wake-up --- */
-void init_timer(void)
-{
-    RTC.CLKSEL = RTC_CLKSEL_INT1K_gc; // 1 kHz ULP clock for RTC
-    while (RTC.STATUS > 0)
-    {
-    } // Wait for sync
-
-    RTC.PITINTCTRL = RTC_PI_bm;        // Enable PIT interrupt
-    RTC.PITCTRLA = RTC_PERIOD_CYC64_gc // ≈64 ms wake-up (~50 ms)
-                   | RTC_PITEN_bm;     // Enable PIT
-}
-
-ISR(RTC_PIT_vect)
-{
-    RTC.PITINTFLAGS = RTC_PI_bm; // Clear interrupt flag
-}
-
-/* --- MAIN --- */
+/**
+ * @brief Main entry point
+ */
 int main(void)
 {
+
+    // Disable unused peripherals for power saving
+    configureLowPower();
+
     // Configure LED pins as outputs
     VPORTA.DIR = (PA1_SET_MASK | PA2_SET_MASK | PA3_SET_MASK | PA6_SET_MASK | PA7_SET_MASK);
     initPWM();
@@ -88,13 +81,7 @@ int main(void)
     bool bLedEnabledOld = bLedEnabled;
     eModeCurrent = ANIMATION_BLINK; // Set the mode to start with
 
-    cli();
-    init_timer();
-    sei();
-
-    set_sleep_mode(SLEEP_MODE_STANDBY);
-
-    while (1)
+    while (true)
     {
         bBtnPressed = handleSwitch(); // Check switch state
 
@@ -131,7 +118,6 @@ int main(void)
             set_sleep_mode(SLEEP_MODE_STANDBY); // Deepest sleep mode (standby)
             sleep_enable();                     // Enable sleep
 
-            cli();       // Disable global interrupts
             sei();       // Re-enable interrupts
             sleep_cpu(); // MCU sleeps here
         }
@@ -156,8 +142,9 @@ int main(void)
             }
         }
 
+        // Sleep during delay instead of busy-wait
         sleep_enable();
-        sleep_cpu(); // Sleep until PIT wakes
+        _delay_ms(MAIN_LOOP_SLEEP);
         sleep_disable();
     }
 }
@@ -170,6 +157,54 @@ static inline void switchMode(void)
     eModeCurrent = (eModeCurrent + 1) % MAX_COUNT;
 }
 
+/**
+ * @brief Configure for lowest power consumption
+ */
+static void configureLowPower(void)
+{
+    // Set unused pins as outputs LOW to prevent floating inputs
+    // Floating inputs can cause extra current consumption
+    PORTA.DIRSET = PIN4_bm | PIN5_bm; // Set PA4, PA5 as outputs if unused
+    PORTA.OUTCLR = PIN4_bm | PIN5_bm; // Drive them LOW
+
+    // Configure sleep mode
+    set_sleep_mode(SLEEP_MODE_IDLE); // Use IDLE when TCA0 PWM needs to run
+    // Use SLEEP_MODE_STANDBY for deep sleep when LEDs are off
+
+    // Disable unused timers
+    TCB0.CTRLA = 0; // Disable TCB0 if not used
+    // TCA0 is used for PWM, keep it enabled
+
+    // Disable ADC (Analog-to-Digital Converter)
+    ADC0.CTRLA &= ~ADC_ENABLE_bm;
+
+    // Disable AC (Analog Comparator)
+    AC0.CTRLA &= ~AC_ENABLE_bm;
+
+    // Disable unused USART
+    USART0.CTRLB = 0;
+
+    // Disable TWI (I2C) if not used
+    TWI0.MCTRLA = 0;
+    TWI0.SCTRLA = 0;
+
+    // Disable SPI
+    SPI0.CTRLA = 0;
+
+    // Disable Watchdog Timer (if not needed)
+    // Note: WDT can only be disabled during first 4 clock cycles after reset
+    // CCP = CCP_IOREG_gc;
+    // WDT.CTRLA = 0;
+
+    // Disable BOD (Brown-Out Detection) in sleep modes for lower power
+    // This is done via fuses, not runtime configurable
+
+    // Disable digital input buffers on unused pins to save power
+    // Only needed if pins are truly unused (floating)
+    // PORTA.PIN4CTRL = PORT_ISC_INPUT_DISABLE_gc;  // PA4 if unused
+    // PORTA.PIN5CTRL = PORT_ISC_INPUT_DISABLE_gc;  // PA5 if unused
+}
+
 /**
  * @brief Init PWM for PA2
  */
@@ -421,7 +456,7 @@ void ledAnimationBlink(bool resetCounters)
         if (counter >= T250)
         {
             counter = 0;
-            state = 0;
+            state = 0; // restart normal sequence
         }
         break;
     }
@@ -447,14 +482,14 @@ void ledAnimationGlow(void)
     brightness += direction;
 
     // Reverse direction at limits
-    if (brightness >= 100U)
+    if (brightness >= GLOW_BRIGHTNESS_MAX)
     {
-        brightness = 100U;
+        brightness = GLOW_BRIGHTNESS_MAX;
         direction = -1;
     }
-    else if (brightness == 10U)
+    else if (brightness == GLOW_BRIGHTNESS_MIN)
     {
-        brightness = 10U;
+        brightness = GLOW_BRIGHTNESS_MIN;
         direction = 1;
     }