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espressif / esp-idf

Espressif IoT Development Framework. Official development framework for Espressif SoCs.
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ledc_clk_cfg_t has RTC8M option on SoC without this clock (ESP32-C3) (IDFGH-7565) #9125

Open tcbennun opened 2 years ago

tcbennun commented 2 years ago

The definition of the ledc_clk_cfg_t enum in ledc_types.h includes LEDC_USE_RTC8M_CLK for all SoCs. ESP32-C3 does not have such a clock, so this option is ambiguous.

According to the TRM, LEDC_SCLK on ESP32-C3 may be sourced from APB_CLK, FOSC_CLK or XTAL_CLK (though the clock diagram in Figure 6-2 does not indicate that XTAL_CLK is an option!)

(Also, the TRM states that FOSC_CLK is the option to choose in order to generate PWM during light sleep, but the option isn't explicitly available in ESP-IDF, and when forcing the option in the conf register, PWM doesn't generate in light sleep anyway. If anyone has any idea how to make that work, I would appreciate the help!)

songruo commented 2 years ago

RTC8M_CLK is the old name for FOSC_CLK (we are planning to do some refactor to make the clock name unified on all chips), so you can select LEDC_USE_RTC8M_CLK to keep the PWM during light sleep on ESP32C3.

There are two more things you need to make sure before you can see the PWM in sleep:

First is to make sure the gpio pin is configured correctly in sleep mode. The easiest way is probably by calling gpio_sleep_sel_dis(pin_num).

Second is you need to keep the RTC8M_CLK on during sleep by calling esp_sleep_pd_config(ESP_PD_DOMAIN_RTC8M, ESP_PD_OPTION_ON) (if you are on master or release/v4.4, then you don't need to worry about this, this will be done internally).