Hi

Question #1
How to configure the ESP32 RTC with the Arduino platform, to use the external 32KHz crystal for the RTC peripheral?

I have tried the following code and it seems to configure the RTC however, once entering deep sleep mode the device will never wake-up again.

Please see the following code:

#include <soc/rtc.h>
#include <TimeLib.h>
#include <sys/time.h>

#define SYNC_TIMEOUT 60000
#define CALIBRATE_ONE(cali_clk) calibrate_one(cali_clk, #cali_clk)


static uint32_t calibrate_one(rtc_cal_sel_t cal_clk, const char *name)
{
  const uint32_t cal_count = 1000;
  const float factor = (1 << 19) * 1000.0f;
  uint32_t cali_val;
  printf("%s:\n", name);

  for (int i = 0; i < 5; ++i)
  {
    printf("calibrate (%d): ", i);
    cali_val = rtc_clk_cal(cal_clk, cal_count);
    printf("%.3f kHz\n", factor / (float)cali_val);
  }
  return cali_val;
}

// Sync control variable
static volatile uint32_t _syncTime = 0;
//static uint32_t utcOffset = (-3 * 3600);
static uint32_t utcOffset = 0; // Use UTC

void DeepSleep() {
  /*
    First we configure the wake up source
    We set our ESP32 to wake up for an external trigger.
    There are two types for ESP32, ext0 and ext1 .
    ext0 uses RTC_IO to wakeup thus requires RTC peripherals
    to be on while ext1 uses RTC Controller so doesnt need
    peripherals to be powered on.
    Note that using internal pullups/pulldowns also requires
    RTC peripherals to be turned on.
  */

  //esp_sleep_enable_ext0_wakeup(GPIO_NUM_2, 1); //1 = High, 0 = Low
  //If you were to use ext1, you would use it like
  //esp_sleep_enable_ext1_wakeup(BUTTON_PIN_BITMASK,ESP_EXT1_WAKEUP_ANY_HIGH);

  const int ext_wakeup_pin_1 = 2;
  const uint64_t ext_wakeup_pin_1_mask = 1ULL << ext_wakeup_pin_1;
  //const int ext_wakeup_pin_2 = 4;
  //const uint64_t ext_wakeup_pin_2_mask = 1ULL << ext_wakeup_pin_2;

  // printf("Enabling EXT1 wakeup on pins GPIO%d, GPIO%d\n", ext_wakeup_pin_1);
  esp_sleep_enable_ext1_wakeup(ext_wakeup_pin_1_mask, ESP_EXT1_WAKEUP_ANY_HIGH);

  //Go to sleep now

  esp_deep_sleep_start();
  //esp_deep_sleep(1000000LL);
  //ESP.restart();
  Serial.println("This will never be printed");
}

bool go_to_sleep = false;


void IRAM_ATTR ISR() {
  go_to_sleep = true;
}



void setup() {
  Serial.begin(115200);

  // ------------- Start RTC Clock and Calibration --------------
  rtc_clk_32k_bootstrap(512);
  //rtc_clk_32k_bootstrap(512);
  rtc_clk_32k_enable(true);

  uint32_t cal_32k = CALIBRATE_ONE(RTC_CAL_32K_XTAL);
  rtc_clk_slow_freq_set(RTC_SLOW_FREQ_32K_XTAL);

  if (cal_32k == 0)
  {
    printf("32K XTAL OSC has not started up");
  }
  else
  {
    printf("XTAL OSC - Okay");
  }

  if (rtc_clk_32k_enabled())
  {
    Serial.println("OSC Enabled");
  }

  struct timeval now = { 0 };
  settimeofday(&now, NULL);

  //setTime(int hr,int min,int sec,int day, int month, int yr);
  Serial.println("attach Interrupt");
  attachInterrupt(digitalPinToInterrupt(2), ISR, FALLING);
}

void loop() {
  //Start:
  if (go_to_sleep) {
    //detachInterrupt(2);
    Serial.println("\n\nGoing to sleep now");
    go_to_sleep = false;
    //pinMode(2, INPUT);
    DeepSleep();
  }
  //check time once per second
  Serial.print(day());
  Serial.print("/");
  Serial.print(month());
  Serial.print("/");
  Serial.println(year());

  Serial.print(second());
  Serial.print("/");
  Serial.print(minute());
  Serial.print("/");
  Serial.print(hour());

  delay(1000);
}

Does anyone have experience in working with the ESP32 RTC with an external crystal?

Thank You!

 

Sorry I do not have an answer for you, but since I currently have an ESP32 on my bench I'm working with I would appreciate it if your share your results.