try to use timer interrupt

README.md

@@ -76,7 +76,7 @@ Hardware: FT232 USB-UART adapter connected to UPDI with a 4.7 kΩ resistor.
    ```
 4. Flash using pymcuprog:
    ```bash
-    pymcuprog -t uart -u /dev/ttyUSB0 -d attiny202 erase && pymcuprog -t uart -u /dev/ttyUSB0 -d attiny202 write -f build/main.hex
+    pymcuprog -t uart -u /dev/ttyUSB0 -d attiny202 write -f build/main.hex
    ```
 ## Hardware Setup (FT232 → ATtiny202 UPDI)
    ```bash

main.c

@@ -1,7 +1,6 @@
 /**
  * @file main.c
- * @brief Bike rear light implementation for ATTINY202.
- *
+ * @brief Bike rear light implementation for ATTINY202 with low-power standby.
  */
 
 #include <stdint.h>
@@ -11,38 +10,47 @@
 #include <avr/sleep.h>
 #include <avr/interrupt.h>
 
-#define BUTTON_PIN_MASK 0x01 // PA0 used as RESET/UPDI pin
-#define PA1_SET_MASK 0x02    ///< LED 1–2
-#define PA2_SET_MASK 0x04    ///< LED 3–6
-#define PA3_SET_MASK 0x08    ///< LED 7–8
-#define PA6_SET_MASK 0x40    ///< Green LED pin
-#define PA7_SET_MASK 0x80    ///< Red LED
+#define BUTTON_PIN_MASK 0x01 // PA0
+#define PA1_SET_MASK 0x02    // LED 1–2
+#define PA2_SET_MASK 0x04    // LED 3–6
+#define PA3_SET_MASK 0x08    // LED 7–8
+#define PA6_SET_MASK 0x40    // Green LED
+#define PA7_SET_MASK 0x80    // Red LED
 
-#define MAIN_LOOP_SLEEP 10U                 // Main loop delay in ms
+#define MAIN_LOOP_SLEEP 50U                 // Loop period in ms
 #define BUTTON_LONG_PRESS_DURATION_MS 1000U // Long 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 BUTTON_IGNORE_DURATION_MS 1000U     // Ignore after long press
 
-/** Convert milliseconds to system ticks */
 #define MS_TO_TICKS(ms) ((ms) / MAIN_LOOP_SLEEP)
 
-/** Global flags */
-volatile bool bLedEnabled = true;
+volatile bool bLedEnabled = false;
 volatile bool bBtnPressed = false;
 
-// Forward declarations
-void blinkLed(bool resetCounters);
 static inline void leds_off(void);
 static inline void leds_on(void);
 static void battery_level_indicator(void);
 static void handleSwitch(void);
-static void software_reset(void);
-ISR(PORTA_PORT_vect);
+void blinkLed(bool resetCounters);
 
-/**
- * @brief Main entry point
- */
+/* --- 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 --- */
 int main(void)
 {
     // Configure LED pins as outputs
@@ -58,7 +66,13 @@ int main(void)
 
     bool bLedEnabledOld = bLedEnabled;
 
-    while (true)
+    cli();
+    init_timer();
+    sei();
+
+    set_sleep_mode(SLEEP_MODE_STANDBY);
+
+    while (1)
     {
         handleSwitch(); // Check switch state
 
@@ -72,32 +86,19 @@ int main(void)
             leds_off();
         }
 
-        // Long press detected --> show confirmation blink
+        // Long press detected → show confirmation blink
         if (bLedEnabledOld != bLedEnabled)
         {
             bLedEnabledOld = bLedEnabled;
 
-            for (uint8_t i = 0U; i < BUTTON_CONFIRMATION_BLINK_LOOPS; i++)
-            {
             leds_off();
-                _delay_ms(BUTTON_CONFIRMATION_BLINK_DURATION_MS);
+            _delay_ms(BUTTON_IGNORE_DURATION_MS / 10);
             leds_on();
-                _delay_ms(BUTTON_CONFIRMATION_BLINK_DURATION_MS);
+            _delay_ms(BUTTON_IGNORE_DURATION_MS / 10);
             leds_off();
-            }
-
-            // Give time until button is released
             _delay_ms(BUTTON_IGNORE_DURATION_MS);
 
-            // Activate the interrupt for PA0
-            PORTA.PIN0CTRL = PORT_PULLUPEN_bm | PORT_ISC_FALLING_gc;
-
-            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
+            blinkLed(true); // reset blink state machine
         }
         else
         {
@@ -107,7 +108,9 @@ int main(void)
             }
         }
 
-        _delay_ms(MAIN_LOOP_SLEEP);
+        sleep_enable();
+        sleep_cpu(); // Sleep until PIT wakes
+        sleep_disable();
     }
 }
 
@@ -168,32 +171,6 @@ static void handleSwitch(void)
     prevPressed = pressed;
 }
 
-/**
- * @brief Perform software reset
- */
-static void software_reset(void)
-{
-    CCP = CCP_IOREG_gc; // unlock protected registers
-    RSTCTRL.SWRR = 1;   // trigger software reset
-    while (1)
-        ; // wait for reset
-}
-
-/**
- * @brief Interrupt service routine
- */
-ISR(PORTA_PORT_vect)
-{
-    // Clear interrupt flags for PA0
-    PORTA.INTFLAGS = BUTTON_PIN_MASK;
-
-    if (!(VPORTA.IN & BUTTON_PIN_MASK)) // check PA0 low
-    {
-        // Turn off all LEDs
-        software_reset();
-    }
-}
-
 /**
  * @brief LED blink state machine (bike rear light style)
  *
@@ -324,7 +301,7 @@ void blinkLed(bool resetCounters)
         if (counter >= T250)
         {
             counter = 0;
-            state = 0; // restart normal sequence
+            state = 0;
         }
         break;
     }