ATtiny3224: PWM 出力 （ソフトウェア版）

PIN_PA5 に 170Hz の PWM出力をします。

プログラム

pwm04/pwm04.ino

// ----------------------------------------------------------------
/*
	pwm04.ino
				Sep/21/2025
*/
// ----------------------------------------------------------------
#define	PROGRAM	"pwm04.ino"
#define	VERSION	"2025-09-21 PM 13:33"

// 20MHz, target 300Hz software PWM for PA5 (works with TinyCore 0.3.0)

#define LED_PIN PIN_PA5

// 170Hz の周期（マイクロ秒）
const uint32_t TARGET_HZ = 170;
const uint32_t PERIOD_US = 1000000UL / TARGET_HZ;
	// = 3333 us (実測周波数 = 1000000/3333 ≈ 300.03 Hz)

// ----------------------------------------------------------------
void setup() {
	Serial1.begin(19200);
	delay(200);
	Serial1.println("*** setup start ***");
	delay(1000);
	Serial1.println("*** ATtiny3224 ***");
	Serial1.println(PROGRAM);
        delay(1000);
        Serial1.println(VERSION);
        delay(1000);

  Serial1.print("CPU Clock = "); Serial1.println(F_CPU);
  Serial1.print("Using software PWM at approx "); Serial1.print(1000000.0f / (float)PERIOD_US, 3);
  Serial1.println(" Hz");
  pinMode(LED_PIN, OUTPUT);
}

// ----------------------------------------------------------------
// duty: 0..255
void pwmRunFor(uint8_t duty8, uint32_t duration_ms) {
  uint32_t cycles = (duration_ms * 1000UL) / PERIOD_US;
  uint32_t high_us = (uint32_t)((uint64_t)(PERIOD_US) * (uint32_t)duty8 / 255ULL);

  // 特殊値の最適化
  if (duty8 == 0) {
    digitalWrite(LED_PIN, LOW);
    delay(duration_ms);
    return;
  }
  if (duty8 == 255) {
    digitalWrite(LED_PIN, HIGH);
    delay(duration_ms);
    return;
  }

  for (uint32_t i = 0; i < cycles; ++i) {
    if (high_us > 0) {
      digitalWrite(LED_PIN, HIGH);
      if (high_us > 1) delayMicroseconds(high_us);
      else __asm__ __volatile__ ("nop");
    }
    uint32_t low_us = PERIOD_US - high_us;
    if (low_us > 0) {
      digitalWrite(LED_PIN, LOW);
      if (low_us > 4) delayMicroseconds(low_us); // delayMicroseconds は 1us 単位
      else for (volatile uint8_t k=0;k< (uint8_t)low_us; ++k) __asm__ __volatile__ ("nop");
    }
  }
}

// ----------------------------------------------------------------
void loop() {
  // テスト：0->64->128->192->255->0 の各デューティを1秒ずつ表示
  uint8_t dutySteps[] = {0, 32, 64, 128, 0};
  for (int i=0;i < sizeof(dutySteps)/sizeof(dutySteps[0]); ++i) {
    uint8_t d = dutySteps[i];
    Serial1.print("Setting duty (0..255) = "); Serial1.println(d);
    pwmRunFor(d, 1000);
		// 1000ms = 1秒
    delay(1000);
		// 少し余裕
  }
}

// ----------------------------------------------------------------

シリアルの出力

*** setup start ***
*** ATtiny3224 ***
pwm04.ino
2025-09-21 PM 13:33
CPU Clock = 20000000
Using software PWM at approx 170.010 Hz
Setting duty (0..255) = 0
Setting duty (0..255) = 32
Setting duty (0..255) = 64
Setting duty (0..255) = 128
Setting duty (0..255) = 0
Setting duty (0..255) = 0
Setting duty (0..255) = 32
Setting duty (0..255) = 64