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ulp_set_wakeup_period() function
Set one of ULP wakeup period values ULP coprocessor starts running the program when the wakeup timer counts up to a given value (called period). There are 5 period values which can be programmed into SENS_ULP_CP_SLEEP_CYCx_REG registers, x = 0..4 for ESP32, and one period value which can be programmed into RTC_CNTL_ULP_CP_TIMER_1_REG register for ESP32-S2/S3. By default, for ESP32, wakeup timer will use the period set into SENS_ULP_CP_SLEEP_CYC0_REG, i.e. period number 0. ULP program code can use SLEEP instruction to select which of the SENS_ULP_CP_SLEEP_CYCx_REG should be used for subsequent wakeups. However, please note that SLEEP instruction issued (from ULP program) while the system is in deep sleep mode does not have effect, and sleep cycle count 0 is used. For ESP32-S2/S3 the SLEEP instruction not exist. Instead a WAKE instruction will be used.
Syntax
Implemented in ![]()
ulp_common.c:20
Return value
- ESP_OK on success - ESP_ERR_INVALID_ARG if period_index is out of range
Notes
The ULP FSM requires two clock cycles to wakeup before being able to run the program. Then additional 16 cycles are reserved after wakeup waiting until the 8M clock is stable. The FSM also requires two more clock cycles to go to sleep after the program execution is halted. The minimum wakeup period that may be set up for the ULP is equal to the total number of cycles spent on the above internal tasks. For a default configuration of the ULP running at 150kHz it makes about 133us.