Deep_sleep overnight

philpep54 · May 11, 2020, 12:11pm

Hey guys, i researched on the topic of deep sleep for the ESP32 but most of what i found is only for a couple of second or minutes. I am currently looking into automation in my greenhouse and since i wont use it during the night i was wondering if it’s possible to set up deep sleep overnight? Or if there is other alternatives instead of deep sleep? Thank you in advance!!

maxgerhardt · May 11, 2020, 1:41pm

Source? When I look into the ESP-IDF code

github.com

espressif/esp-idf/blob/045aaf6fb0e1c7bc121088a6457873ddf86badee/components/soc/esp32/rtc_time.c#L132


      
              rtc_xtal_freq_t xtal_freq = rtc_clk_xtal_freq_get();
              uint64_t xtal_cycles = rtc_clk_cal_internal(cal_clk, slowclk_cycles);
              uint64_t divider = ((uint64_t)xtal_freq) * slowclk_cycles;
              uint64_t period_64 = ((xtal_cycles << RTC_CLK_CAL_FRACT) + divider / 2 - 1) / divider;
              uint32_t period = (uint32_t)(period_64 & UINT32_MAX);
              return period;
          }
          
          uint64_t rtc_time_us_to_slowclk(uint64_t time_in_us, uint32_t period)
          {
              /* Overflow will happen in this function if time_in_us >= 2^45, which is about 400 days.
               * TODO: fix overflow.
               */
              return (time_in_us << RTC_CLK_CAL_FRACT) / period;
          }
          
          uint64_t rtc_time_slowclk_to_us(uint64_t rtc_cycles, uint32_t period)
          {
              return (rtc_cycles * period) >> RTC_CLK_CAL_FRACT;
          }

If the wakeup source is the RTC timer, and it is fed by RTC slow clock, up to 400 days of sleep should be possible before an overflow occurs.

Also here a user comments that you have to be careful to use 64-bit constants (ULL suffix) so that the computed time in microseconds to sleep is not internally overflowing to a cut-off 32-bit version.

https://github.com/espressif/arduino-esp32/blob/master/tools/sdk/include/esp32/esp_sleep.h#L110

Also this issue says that the module should need a 32.768kHz watch crystal if you expected very accurate wake-up time without a drift by a few minutes.

philpep54 · May 11, 2020, 1:59pm

Oh i must have looked for the wrong thing then, my question was mostly to find out if it was possible to do that with deep sleep or if something else was more usefull !! thank you ill try this out !