ESP32-C3轻度休眠时序问题求解

我对 ESP32-C3 进入 light-sleep 和从 light-sleep 唤醒需要多长时间很感兴趣，但我找不到任何发布的内容，所以我做了一些实验。我想我会在这里为其他人发布结果。

我写了一些代码进入进入 Light-Sleep 的循环，然后在 GPIO (4) 变高时醒来。我还在这个过程中设置了另一个 GPIO (13)，这样我就可以在我的示波器上查看时序。

这是基本循环。它在以 160 MHz 运行的 ESP32-C3 开发板上使用 Arduino 环境以及一些 IDF API 调用。

代码：全选
  // Go into an infinite loop of Light-Sleeps waiting on a GPIO to wake us up.
  // - GPIO04 - Wake-up Pin - Feed 100 Hz (3.3V) into this
  //          - This is level based, so it will wake up as long as it is high.
  //          - If it is already high, we will wake up right away.
  // - GPIO13 - Sleep-Indicator pin
  uint32_t CpuCountS;     // Count of CPU cycles
  uint32_t CpuCountE;
  uint64_t MicrosS;       // From ESP microseconds timer
  uint64_t MicrosE;
  
  pinMode(GPIO_NUM_4, INPUT);
  pinMode(GPIO_NUM_13, OUTPUT);

  gpio_wakeup_enable(GPIO_NUM_4, GPIO_INTR_HIGH_LEVEL);    // Enable wakeup on high-level on GPIO 4
  esp_sleep_enable_gpio_wakeup();                          // Enable wake-up via GPIO pin level
   
  // Infinite loop
  for (uint16_t i; ; i++) {
      
    while (digitalRead(GPIO_NUM_4) == HIGH) {}             // Loop until the pin is low since we don't want to wake up right away
      
    MicrosS =  esp_timer_get_time();
    CpuCountS = cpu_hal_get_cycle_count();

    GPIO.out_w1ts.out_w1ts = (1 << GPIO_NUM_13);           // Extra-fast - Set HIGH
    esp_light_sleep_start();
    GPIO.out_w1tc.out_w1tc = (1 << GPIO_NUM_13);           // Extra-fast - Set LOW
      
    CpuCountE = cpu_hal_get_cycle_count();
    MicrosE = esp_timer_get_time();
      
    printf("Sleep wake-up via GPIO after: %10.6f secs clock. %10.6f secs CPU.n",
           (MicrosE - MicrosS)/1000000.0, (CpuCountE - CpuCountS)/(1000000.0 * 160));
  }

  // Cleanup wakeup settings even though this will never be executed in this code.
  esp_sleep_disable_wakeup_source(ESP_SLEEP_WAKEUP_GPIO);
  gpio_wakeup_disable(GPIO_NUM_4);

然后我将大约 100 Hz 的方波馈入 GPIO 4，并观察 GPIO 13 以查看 ESP 何时进入和退出睡眠模式。

我进行一系列测量的笔记是：
代码：全选
Light Sleep Timing Data

- Going to sleep:
      +  0 us - GPIO13 goes high - Just before the Sleep call.
      +320 us - GPIO 13 goes Hi-z
              - Voltage drops to Vcc/2 in a couple of us.
              - Drops to zero in < 5us when pulled low by 20K ohms
      +600 us - Drops to zero loaded with a 1x scope probe.
      +900 us - Drops to zero loaded with a 10x scope probe.

  - Basically,  sleep is entered about 320 us after the esp_light_sleep_start() call.

- Waking up:
     +      0 us - GPIO 4 goes high to wake up the ESP32
     +280-290 us - GPIO 13 goes high again as pin returns to output-high from hi-z sleep mode
     +490-500 us - GPIO 13 goes low, set by code immediately after sleep returns.

- The time returned by esp_timer_get_time() pretty accurately measures the true elapsed time
   including the sleep period.
- The time returned by cpu_hal_get_cycle_count() is always about 250 us over the sleep period
   regardless of the sleep length.
   - That seems to be how long the CPU actually executes during the sleep entry and exit.

所以最重要的是，进入 Light Sleep 模式大约需要 320 us，然后大约需要 500 us 才能恢复正常执行。信号中有大约 10-20us 的抖动。

以下是串行控制台的几行：

代码：全选
Sleep wake-up via GPIO after:   0.000989 secs clock.   0.000244 secs CPU.
Sleep wake-up via GPIO after:   0.001002 secs clock.   0.000243 secs CPU.
Sleep wake-up via GPIO after:   0.000995 secs clock.   0.000249 secs CPU.
Sleep wake-up via GPIO after:   0.001001 secs clock.   0.000250 secs CPU.
Sleep wake-up via GPIO after:   0.000992 secs clock.   0.000250 secs CPU.
Sleep wake-up via GPIO after:   0.001000 secs clock.   0.000250 secs CPU.
Sleep wake-up via GPIO after:   0.000994 secs clock.   0.000245 secs CPU.
Sleep wake-up via GPIO after:   0.000993 secs clock.   0.000245 secs CPU.
Sleep wake-up via GPIO after:   0.001002 secs clock.   0.000243 secs CPU.
Sleep wake-up via GPIO after:   0.001003 secs clock.   0.000249 secs CPU.
Sleep wake-up via GPIO after:   0.001000 secs clock.   0.000251 secs CPU.
Sleep wake-up via GPIO after:   0.000993 secs clock.   0.000251 secs CPU.
Sleep wake-up via GPIO after:   0.001001 secs clock.   0.000250 secs CPU.
Sleep wake-up via GPIO after:   0.000989 secs clock.   0.000244 secs CPU.
Sleep wake-up via GPIO after:   0.000995 secs clock.   0.000245 secs CPU.
Sleep wake-up via GPIO after:   0.001002 secs clock.   0.000244 secs CPU.
Sleep wake-up via GPIO after:   0.000995 secs clock.   0.000244 secs CPU.