![]() While ext0 can only be assigned to one pin, ext1 can be assigned to a map of different pins. There are a few things to consider when using the ULP core: Only the pins that can be accessed by the RTC can be used (RTC GPIO). Also I found that the internal pullup/pulldown setting are not reliable. The two external wakeups are ext0 and ext1. For this project GPIO interrupts are needed as the device should wake up with the press of a button. The ESP32 can activated by different wakeup sources. Luckily Espressif has an example for a blinking LED that does exactly what I wanted: The ULP can be woken up periodically by the RTC using:įor the 1Hz signal the ULP coprocessor has to be programmed in assembler. This Ultra Low Power processor can do basic tasks like checking sensors or reading and writing pin states while only needing ~150♚. ![]() The RTC itself can't do much, but it can wake the ESP32's third core, the ULP coprocessor. During this, the internal Real Time Clock controller is still active. ![]() In sleep mode the ESP32's main cores are powered down, reducing the current to only 10♚. But not everyone knows that it has some nice power saving features. This means that part of the ESP32 needs to remain active during standby mode.Īt 70-200mA, the ESP32 can be power-hungry with its dual cores and WiFi modem. Although the memory display does not need constant refreshing over SPI, a >1Hz clock signal must be supplied to its EXTCOMM pin. There are a few things necessary to keep the display active and the battery life long. This way the device would be usable as a clock and calendar. ![]() While the battery can power the handheld for only a few hours, I wanted to include a standby mode that utilizes the low power display. ![]()
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