时钟树

[English]

ESP32 的时钟子系统用于从一系列根时钟中提取并分配系统/模块时钟。时钟树驱动程序负责维护系统时钟的基本功能，并管理模块时钟间的复杂关系。

本文档首先介绍了根时钟和模块时钟，随后介绍了可供用户调用的时钟树 API，调用这些 API，可以监测模块时钟的运行状态。

简介

本节列出了 ESP32 支持的根时钟和模块时钟的定义，这些定义通常用于驱动程序配置，有助于为外设选择合适的时钟源。

根时钟

根时钟会产生可靠的时钟信号，经各种门、复用器、分频器或倍频器传递，这些时钟信号最终成为 CPU 内核、Wi-Fi、蓝牙、RTC 及外设等功能模块的时钟源。

ESP32 的根时钟列在 soc_root_clk_t 中：

• 内部 8 MHz RC 振荡器 (RC_FAST)

  此 RC 振荡器可产生约 8.5 MHz 的时钟信号输出，标识为 RC_FAST_CLK。

  此约 8.5 MHz 的信号也会传入可配置的分频器，默认情况下，该分频器会将输入的时钟频率分频 256 倍，生成信号 RC_FAST_D256_CLK。

  在运行时，通过在 RC_FAST_D256_CLK 上校准，可以计算 RC_FAST_CLK 的实际频率。

• 外部 2 ~ 40 MHz 晶振 (XTAL)

• 内部 150 kHz RC 振荡器 (RC_SLOW)

  此 RC 振荡器产生约 150 kHz 的时钟信号输出，标识为 RC_SLOW_CLK。在运行时，通过校准，可以计算该时钟信号的实际频率。

• 外部 32 kHz 晶振 - 可选 (XTAL32K)

  XTAL32K_CLK 的时钟源可以是连接到 32K_XP 和 32K_XN 管脚的 32 kHz 晶振，也可以是外部电路生成的 32 kHz 时钟信号。如果使用外部电路生成的时钟信号，该信号必须连接到 32K_XN 管脚，并且在 32K_XP 管脚和地之间连接一个 1 nF 的电容。此时，32K_XP 管脚不能用作 GPIO 管脚。

  通过校准，可以计算 XTAL32K_CLK 的实际频率。

与晶振产生的信号相比，从 RC 振荡器电路产生的信号通常精度较低，且容易受环境影响。因此，ESP32 为 RTC_SLOW_CLK 提供了几种时钟源选项，可以根据对系统时间精度和对功耗的要求选择。更多详情，请参阅 RTC 定时器时钟源。

模块时钟

ESP32 的可用模块时钟在 soc_module_clk_t 中列出，每个模块时钟都有其唯一 ID。查阅文档中的枚举值，即可获取各模块时钟的详细信息。

使用 API

时钟树驱动程序提供了一个一体化接口，可以获取模块时钟的频率，即 esp_clk_tree_src_get_freq_hz()。通过该函数，你可以在任何时刻，通过提供时钟名称 soc_module_clk_t 和指定返回频率值的精度级别 esp_clk_tree_src_freq_precision_t，获取时钟频率。

API 参考

Header File

• components/soc/esp32/include/soc/clk_tree_defs.h

• This header file can be included with:

  #include "soc/clk_tree_defs.h"
  

Macros

SOC_CLK_RC_FAST_FREQ_APPROX

Approximate RC_FAST_CLK frequency in Hz

SOC_CLK_RC_SLOW_FREQ_APPROX

Approximate RC_SLOW_CLK frequency in Hz

SOC_CLK_RC_FAST_D256_FREQ_APPROX

Approximate RC_FAST_D256_CLK frequency in Hz

SOC_CLK_XTAL32K_FREQ_APPROX

Approximate XTAL32K_CLK frequency in Hz

SOC_GPTIMER_CLKS

Array initializer for all supported clock sources of GPTimer.

The following code can be used to iterate all possible clocks:

soc_periph_gptimer_clk_src_t gptimer_clks[] = (soc_periph_gptimer_clk_src_t)SOC_GPTIMER_CLKS;
for (size_t i = 0; i< sizeof(gptimer_clks) / sizeof(gptimer_clks[0]); i++) {
    soc_periph_gptimer_clk_src_t clk = gptimer_clks[i];
// Test GPTimer with the clock `clk`
}

SOC_LCD_CLKS

Array initializer for all supported clock sources of LCD.

SOC_RMT_CLKS

Array initializer for all supported clock sources of RMT.

SOC_UART_CLKS

Array initializer for all supported clock sources of UART.

SOC_MCPWM_TIMER_CLKS

Array initializer for all supported clock sources of MCPWM Timer.

SOC_MCPWM_CAPTURE_CLKS

Array initializer for all supported clock sources of MCPWM Capture Timer.

SOC_MCPWM_CARRIER_CLKS

Array initializer for all supported clock sources of MCPWM Carrier.

SOC_I2S_CLKS

Array initializer for all supported clock sources of I2S.

SOC_I2C_CLKS

Array initializer for all supported clock sources of I2C.

SOC_SPI_CLKS

Array initializer for all supported clock sources of SPI.

SOC_SDM_CLKS

Array initializer for all supported clock sources of SDM.

SOC_DAC_DIGI_CLKS

Array initializer for all supported clock sources of DAC digital controller.

SOC_DAC_COSINE_CLKS

Array initializer for all supported clock sources of DAC cosine wave generator.

SOC_TWAI_CLKS

Array initializer for all supported clock sources of TWAI.

SOC_ADC_DIGI_CLKS

Array initializer for all supported clock sources of ADC digital controller.

SOC_ADC_RTC_CLKS

Array initializer for all supported clock sources of ADC RTC controller.

SOC_MWDT_CLKS

Array initializer for all supported clock sources of MWDT.

SOC_LEDC_CLKS

Array initializer for all supported clock sources of LEDC.

SOC_SDMMC_CLKS

Array initializer for all supported clock sources of SDMMC.

Enumerations

enum soc_root_clk_t

Root clock.

Values:

enumerator SOC_ROOT_CLK_INT_RC_FAST

Internal 8MHz RC oscillator

enumerator SOC_ROOT_CLK_INT_RC_SLOW

Internal 150kHz RC oscillator

enumerator SOC_ROOT_CLK_EXT_XTAL

External 2~40MHz crystal

enumerator SOC_ROOT_CLK_EXT_XTAL32K

External 32kHz crystal/clock signal

enum soc_cpu_clk_src_t

CPU_CLK mux inputs, which are the supported clock sources for the CPU_CLK.

备注

Enum values are matched with the register field values on purpose

Values:

enumerator SOC_CPU_CLK_SRC_XTAL

Select XTAL_CLK as CPU_CLK source

enumerator SOC_CPU_CLK_SRC_PLL

Select PLL_CLK as CPU_CLK source (PLL_CLK is the output of 40MHz crystal oscillator frequency multiplier, can be 480MHz or 320MHz)

enumerator SOC_CPU_CLK_SRC_RC_FAST

Select RC_FAST_CLK as CPU_CLK source

enumerator SOC_CPU_CLK_SRC_APLL

Select APLL_CLK as CPU_CLK source

enumerator SOC_CPU_CLK_SRC_INVALID

Invalid CPU_CLK source

enum soc_rtc_slow_clk_src_t

RTC_SLOW_CLK mux inputs, which are the supported clock sources for the RTC_SLOW_CLK.

备注

Enum values are matched with the register field values on purpose

Values:

enumerator SOC_RTC_SLOW_CLK_SRC_RC_SLOW

Select RC_SLOW_CLK as RTC_SLOW_CLK source

enumerator SOC_RTC_SLOW_CLK_SRC_XTAL32K

Select XTAL32K_CLK as RTC_SLOW_CLK source

enumerator SOC_RTC_SLOW_CLK_SRC_RC_FAST_D256

Select RC_FAST_D256_CLK (referred as FOSC_DIV or 8m_d256/8md256 in TRM and reg. description) as RTC_SLOW_CLK source

enumerator SOC_RTC_SLOW_CLK_SRC_INVALID

Invalid RTC_SLOW_CLK source

enum soc_rtc_fast_clk_src_t

RTC_FAST_CLK mux inputs, which are the supported clock sources for the RTC_FAST_CLK.

备注

Enum values are matched with the register field values on purpose

Values:

enumerator SOC_RTC_FAST_CLK_SRC_XTAL_D4

Select XTAL_D4_CLK (may referred as XTAL_CLK_DIV_4) as RTC_FAST_CLK source

enumerator SOC_RTC_FAST_CLK_SRC_XTAL_DIV

Alias name for SOC_RTC_FAST_CLK_SRC_XTAL_D4

enumerator SOC_RTC_FAST_CLK_SRC_RC_FAST

Select RC_FAST_CLK as RTC_FAST_CLK source

enumerator SOC_RTC_FAST_CLK_SRC_INVALID

Invalid RTC_FAST_CLK source

enum soc_xtal_freq_t

Possible main XTAL frequency options on the target.

备注

Enum values equal to the frequency value in MHz

备注

Not all frequency values listed here are supported in IDF. Please check SOC_XTAL_SUPPORT_XXX in soc_caps.h for the supported ones.

Values:

enumerator SOC_XTAL_FREQ_AUTO

Automatic XTAL frequency detention

enumerator SOC_XTAL_FREQ_24M

24MHz XTAL

enumerator SOC_XTAL_FREQ_26M

26MHz XTAL

enumerator SOC_XTAL_FREQ_40M

40MHz XTAL

enum soc_module_clk_t

Supported clock sources for modules (CPU, peripherals, RTC, etc.)

备注

enum starts from 1, to save 0 for special purpose

Values:

enumerator SOC_MOD_CLK_CPU

CPU_CLK can be sourced from XTAL, PLL, RC_FAST, or APLL by configuring soc_cpu_clk_src_t

enumerator SOC_MOD_CLK_RTC_FAST

RTC_FAST_CLK can be sourced from XTAL_D4 or RC_FAST by configuring soc_rtc_fast_clk_src_t

enumerator SOC_MOD_CLK_RTC_SLOW

RTC_SLOW_CLK can be sourced from RC_SLOW, XTAL32K, or RC_FAST_D256 by configuring soc_rtc_slow_clk_src_t

enumerator SOC_MOD_CLK_APB

APB_CLK is highly dependent on the CPU_CLK source

enumerator SOC_MOD_CLK_PLL_D2

PLL_D2_CLK is derived from PLL, it has a fixed divider of 2

enumerator SOC_MOD_CLK_PLL_F160M

PLL_F160M_CLK is derived from PLL, and has a fixed frequency of 160MHz

enumerator SOC_MOD_CLK_XTAL32K

XTAL32K_CLK comes from the external 32kHz crystal, passing a clock gating to the peripherals

enumerator SOC_MOD_CLK_RC_FAST

RC_FAST_CLK comes from the internal 8MHz rc oscillator, passing a clock gating to the peripherals

enumerator SOC_MOD_CLK_RC_FAST_D256

RC_FAST_D256_CLK comes from the internal 8MHz rc oscillator, divided by 256, and passing a clock gating to the peripherals

enumerator SOC_MOD_CLK_XTAL

XTAL_CLK comes from the external crystal (2~40MHz)

enumerator SOC_MOD_CLK_REF_TICK

REF_TICK is derived from APB, it has a fixed frequency of 1MHz even when APB frequency changes

enumerator SOC_MOD_CLK_APLL

APLL is sourced from PLL, and its frequency is configurable through APLL configuration registers

enumerator SOC_MOD_CLK_INVALID

Indication of the end of the available module clock sources

enum soc_periph_systimer_clk_src_t

Type of SYSTIMER clock source.

Values:

enumerator SYSTIMER_CLK_SRC_XTAL

SYSTIMER source clock is XTAL

enumerator SYSTIMER_CLK_SRC_DEFAULT

SYSTIMER source clock default choice is XTAL

enum soc_periph_gptimer_clk_src_t

Type of GPTimer clock source.

Values:

enumerator GPTIMER_CLK_SRC_APB

Select APB as the source clock

enumerator GPTIMER_CLK_SRC_DEFAULT

Select APB as the default choice

enum soc_periph_tg_clk_src_legacy_t

Type of Timer Group clock source, reserved for the legacy timer group driver.

Values:

enumerator TIMER_SRC_CLK_APB

Timer group source clock is APB

enumerator TIMER_SRC_CLK_DEFAULT

Timer group source clock default choice is APB

enum soc_periph_lcd_clk_src_t

Type of LCD clock source.

Values:

enumerator LCD_CLK_SRC_PLL160M

Select PLL_160M as the source clock

enumerator LCD_CLK_SRC_DEFAULT

Select PLL_160M as the default choice

enum soc_periph_rmt_clk_src_t

Type of RMT clock source.

Values:

enumerator RMT_CLK_SRC_APB

Select APB as the source clock

enumerator RMT_CLK_SRC_REF_TICK

Select REF_TICK as the source clock

enumerator RMT_CLK_SRC_DEFAULT

Select APB as the default choice

enum soc_periph_rmt_clk_src_legacy_t

Type of RMT clock source, reserved for the legacy RMT driver.

Values:

enumerator RMT_BASECLK_APB

RMT source clock is APB CLK

enumerator RMT_BASECLK_REF

RMT source clock is REF_TICK

enumerator RMT_BASECLK_DEFAULT

RMT source clock default choice is APB

enum soc_periph_uart_clk_src_legacy_t

Type of UART clock source, reserved for the legacy UART driver.

Values:

enumerator UART_SCLK_APB

UART source clock is APB CLK

enumerator UART_SCLK_REF_TICK

UART source clock is REF_TICK

enumerator UART_SCLK_DEFAULT

UART source clock default choice is APB

enum soc_periph_mcpwm_timer_clk_src_t

Type of MCPWM timer clock source.

Values:

enumerator MCPWM_TIMER_CLK_SRC_PLL160M

Select PLL_F160M as the source clock

enumerator MCPWM_TIMER_CLK_SRC_DEFAULT

Select PLL_F160M as the default clock choice

enum soc_periph_mcpwm_capture_clk_src_t

Type of MCPWM capture clock source.

Values:

enumerator MCPWM_CAPTURE_CLK_SRC_APB

Select APB as the source clock

enumerator MCPWM_CAPTURE_CLK_SRC_DEFAULT

Select APB as the default clock choice

enum soc_periph_mcpwm_carrier_clk_src_t

Type of MCPWM carrier clock source.

Values:

enumerator MCPWM_CARRIER_CLK_SRC_PLL160M

Select PLL_F160M as the source clock

enumerator MCPWM_CARRIER_CLK_SRC_DEFAULT

Select PLL_F160M as the default clock choice

enum soc_periph_i2s_clk_src_t

I2S clock source enum.

Values:

enumerator I2S_CLK_SRC_DEFAULT

Select PLL_F160M as the default source clock

enumerator I2S_CLK_SRC_PLL_160M

Select PLL_F160M as the source clock

enumerator I2S_CLK_SRC_APLL

Select APLL as the source clock

enum soc_periph_i2c_clk_src_t

Type of I2C clock source.

Values:

enumerator I2C_CLK_SRC_APB

enumerator I2C_CLK_SRC_DEFAULT

enum soc_periph_spi_clk_src_t

Type of SPI clock source.

Values:

enumerator SPI_CLK_SRC_DEFAULT

Select APB as SPI source clock

enumerator SPI_CLK_SRC_APB

Select APB as SPI source clock

enum soc_periph_sdm_clk_src_t

Sigma Delta Modulator clock source.

Values:

enumerator SDM_CLK_SRC_APB

Select APB as the source clock

enumerator SDM_CLK_SRC_DEFAULT

Select APB as the default clock choice

enum soc_periph_dac_digi_clk_src_t

DAC digital controller clock source.

Values:

enumerator DAC_DIGI_CLK_SRC_PLLD2

Select PLL_D2 as the source clock

enumerator DAC_DIGI_CLK_SRC_APLL

Select APLL as the source clock

enumerator DAC_DIGI_CLK_SRC_DEFAULT

Select PLL_D2 as the default source clock

enum soc_periph_dac_cosine_clk_src_t

DAC cosine wave generator clock source.

Values:

enumerator DAC_COSINE_CLK_SRC_RTC_FAST

Select RTC FAST as the source clock

enumerator DAC_COSINE_CLK_SRC_DEFAULT

Select RTC FAST as the default source clock

enum soc_periph_twai_clk_src_t

TWAI clock source.

Values:

enumerator TWAI_CLK_SRC_APB

Select APB as the source clock

enumerator TWAI_CLK_SRC_DEFAULT

Select APB as the default clock choice

enum soc_periph_adc_digi_clk_src_t

ADC digital controller clock source.

备注

ADC DMA mode is clocked from I2S on ESP32, using ADC_DIGI_ here for compatibility Its clock source is same as I2S

Values:

enumerator ADC_DIGI_CLK_SRC_PLL_F160M

Select F160M as the source clock

enumerator ADC_DIGI_CLK_SRC_APLL

Select APLL as the source clock

enumerator ADC_DIGI_CLK_SRC_DEFAULT

Select F160M as the default clock choice

enum soc_periph_adc_rtc_clk_src_t

ADC RTC controller clock source.

Values:

enumerator ADC_RTC_CLK_SRC_RC_FAST

Select RC_FAST as the source clock

enumerator ADC_RTC_CLK_SRC_DEFAULT

Select RC_FAST as the default clock choice

enum soc_periph_mwdt_clk_src_t

MWDT clock source.

Values:

enumerator MWDT_CLK_SRC_APB

Select APB as the source clock

enumerator MWDT_CLK_SRC_DEFAULT

Select APB as the default clock choice

enum soc_periph_ledc_clk_src_legacy_t

Type of LEDC clock source, reserved for the legacy LEDC driver.

Values:

enumerator LEDC_AUTO_CLK

LEDC source clock will be automatically selected based on the giving resolution and duty parameter when init the timer

enumerator LEDC_USE_APB_CLK

Select APB as the source clock

enumerator LEDC_USE_RC_FAST_CLK

Select RC_FAST as the source clock

enumerator LEDC_USE_REF_TICK

Select REF_TICK as the source clock

enumerator LEDC_USE_RTC8M_CLK

Alias of 'LEDC_USE_RC_FAST_CLK'

enum soc_periph_sdmmc_clk_src_t

Type of SDMMC clock source.

Values:

enumerator SDMMC_CLK_SRC_DEFAULT

Select PLL_160M as the default choice

enumerator SDMMC_CLK_SRC_PLL160M

Select PLL_160M as the source clock

enum soc_clkout_sig_id_t

Values:

enumerator CLKOUT_SIG_I2S0

I2S0 clock, depends on the i2s driver configuration

enumerator CLKOUT_SIG_PLL

PLL_CLK is the output of crystal oscillator frequency multiplier

enumerator CLKOUT_SIG_RC_SLOW

RC slow clock, depends on the RTC_CLK_SRC configuration

enumerator CLKOUT_SIG_XTAL

Main crystal oscillator clock

enumerator CLKOUT_SIG_APLL

Divided by PLL, frequency is configurable

enumerator CLKOUT_SIG_REF_TICK

Divided by APB clock, usually be 1MHz

enumerator CLKOUT_SIG_PLL_F80M

From PLL, usually be 80MHz

enumerator CLKOUT_SIG_RC_FAST

RC fast clock, about 8MHz

enumerator CLKOUT_SIG_I2S1

I2S1 clock, depends on the i2s driver configuration

enumerator CLKOUT_SIG_INVALID

Header File

• components/esp_hw_support/include/esp_clk_tree.h

• This header file can be included with:

  #include "esp_clk_tree.h"
  

Functions

esp_err_t esp_clk_tree_src_get_freq_hz(soc_module_clk_t clk_src, esp_clk_tree_src_freq_precision_t precision, uint32_t *freq_value)

Get frequency of module clock source.

参数

• clk_src -- [in] Clock source available to modules, in soc_module_clk_t

• precision -- [in] Degree of precision, one of esp_clk_tree_src_freq_precision_t values This arg only applies to the clock sources that their frequencies can vary: SOC_MOD_CLK_RTC_FAST, SOC_MOD_CLK_RTC_SLOW, SOC_MOD_CLK_RC_FAST, SOC_MOD_CLK_RC_FAST_D256, SOC_MOD_CLK_XTAL32K For other clock sources, this field is ignored.

• freq_value -- [out] Frequency of the clock source, in Hz

返回

• ESP_OK Success

• ESP_ERR_INVALID_ARG Parameter error

• ESP_FAIL Calibration failed

Enumerations

enum esp_clk_tree_src_freq_precision_t

Degree of precision of frequency value to be returned by esp_clk_tree_src_get_freq_hz()

Values:

enumerator ESP_CLK_TREE_SRC_FREQ_PRECISION_CACHED

enumerator ESP_CLK_TREE_SRC_FREQ_PRECISION_APPROX

enumerator ESP_CLK_TREE_SRC_FREQ_PRECISION_EXACT

enumerator ESP_CLK_TREE_SRC_FREQ_PRECISION_INVALID

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