时钟树

[English]

ESP32-C2 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-C2 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-C2 的根时钟列在 soc_root_clk_t 中：

• 内部 17.5 MHz RC 振荡器 (RC_FAST)

  此 RC 振荡器可产生约 17.5 MHz 的时钟信号输出，标识为 RC_FAST_CLK。

  此约 17.5 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 40/26 MHz 晶振 (XTAL)

• 内部 136 kHz RC 振荡器 (RC_SLOW)

  此 RC 振荡器产生约 136 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。

• 外部慢速时钟 - 可选 (OSC_SLOW)

  将外部电路生成的时钟信号连接到 pin0（时钟信号频率不超过 136 kHz 时），可作为 RTC_SLOW_CLK 的时钟源。通过校准，可以计算该时钟信号的实际频率。

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-C2 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-C2 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/esp32c2/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_OSC_SLOW_FREQ_APPROX

Approximate OSC_SLOW_CLK (external slow clock) 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_TEMP_SENSOR_CLKS

Array initializer for all supported clock sources of Temperature Sensor.

SOC_SPI_CLKS

Array initializer for all supported clock sources of SPI.

SOC_I2C_CLKS

Array initializer for all supported clock sources of I2C.

SOC_ADC_DIGI_CLKS

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

SOC_GLITCH_FILTER_CLKS

Array initializer for all supported clock sources of Glitch Filter.

SOC_MWDT_CLKS

Array initializer for all supported clock sources of MWDT.

SOC_LEDC_CLKS

Array initializer for all supported clock sources of LEDC.

Enumerations

enum soc_root_clk_t

Root clock.

Values:

enumerator SOC_ROOT_CLK_INT_RC_FAST

Internal 17.5MHz RC oscillator

enumerator SOC_ROOT_CLK_INT_RC_SLOW

Internal 136kHz RC oscillator

enumerator SOC_ROOT_CLK_EXT_XTAL

External 26/40MHz crystal

enumerator SOC_ROOT_CLK_EXT_OSC_SLOW

External slow clock signal at pin0, only support 32.768 KHz currently

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 26/40MHz crystal oscillator frequency multiplier, 480MHz)

enumerator SOC_CPU_CLK_SRC_RC_FAST

Select RC_FAST_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_OSC_SLOW

Select OSC_SLOW_CLK (external slow clock) 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_D2

Select XTAL_D2_CLK (may referred as XTAL_CLK_DIV_2) as RTC_FAST_CLK source

enumerator SOC_RTC_FAST_CLK_SRC_XTAL_DIV

Alias name for SOC_RTC_FAST_CLK_SRC_XTAL_D2

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_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, or RC_FAST by configuring soc_cpu_clk_src_t

enumerator SOC_MOD_CLK_RTC_FAST

RTC_FAST_CLK can be sourced from XTAL_D2 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 always 40MHz no matter it derives from XTAL or PLL

enumerator SOC_MOD_CLK_PLL_F40M

PLL_F40M_CLK is derived from PLL, and has a fixed frequency of 40MHz

enumerator SOC_MOD_CLK_PLL_F60M

PLL_F60M_CLK is derived from PLL, and has a fixed frequency of 60MHz

enumerator SOC_MOD_CLK_PLL_F80M

PLL_F80M_CLK is derived from PLL, and has a fixed frequency of 80MHz

enumerator SOC_MOD_CLK_OSC_SLOW

OSC_SLOW_CLK comes from an external slow clock signal, passing a clock gating to the peripherals

enumerator SOC_MOD_CLK_RC_FAST

RC_FAST_CLK comes from the internal 20MHz rc oscillator, passing a clock gating to the peripherals

enumerator SOC_MOD_CLK_RC_FAST_D256

RC_FAST_D256_CLK comes from the internal 20MHz rc oscillator, divided by 256, and passing a clock gating to the peripherals

enumerator SOC_MOD_CLK_XTAL

XTAL_CLK comes from the external 26/40MHz crystal

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_PLL_F40M

Select PLL_F40M as the source clock

enumerator GPTIMER_CLK_SRC_XTAL

Select XTAL as the source clock

enumerator GPTIMER_CLK_SRC_DEFAULT

Select PLL_F40M 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_PLL_F40M

Timer group clock source is PLL_F40M

enumerator TIMER_SRC_CLK_XTAL

Timer group clock source is XTAL

enumerator TIMER_SRC_CLK_DEFAULT

Timer group clock source default choice is PLL_F40M

enum soc_periph_temperature_sensor_clk_src_t

Type of Temp Sensor clock source.

Values:

enumerator TEMPERATURE_SENSOR_CLK_SRC_XTAL

Select XTAL as the source clock

enumerator TEMPERATURE_SENSOR_CLK_SRC_RC_FAST

Select RC_FAST as the source clock

enumerator TEMPERATURE_SENSOR_CLK_SRC_DEFAULT

Select XTAL as the default choice

enum soc_periph_uart_clk_src_legacy_t

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

Values:

enumerator UART_SCLK_PLL_F40M

UART source clock is PLL_F40M CLK

enumerator UART_SCLK_RTC

UART source clock is RC_FAST

enumerator UART_SCLK_XTAL

UART source clock is XTAL

enumerator UART_SCLK_DEFAULT

UART source clock default choice is PLL_F40M

enum soc_periph_spi_clk_src_t

Type of SPI clock source.

Values:

enumerator SPI_CLK_SRC_DEFAULT

Select PLL_40M as SPI source clock

enumerator SPI_CLK_SRC_PLL_F40M

Select PLL_40M as SPI source clock

enumerator SPI_CLK_SRC_XTAL

Select XTAL as SPI source clock

enum soc_periph_i2c_clk_src_t

Type of I2C clock source.

Values:

enumerator I2C_CLK_SRC_XTAL

Select XTAL as the source clock

enumerator I2C_CLK_SRC_RC_FAST

Select RC_FAST as the source clock

enumerator I2C_CLK_SRC_DEFAULT

Select XTAL as the default clock choice

enum soc_periph_adc_digi_clk_src_t

ADC digital controller clock source.

Values:

enumerator ADC_DIGI_CLK_SRC_XTAL

Select XTAL as the source clock

enumerator ADC_DIGI_CLK_SRC_PLL_F80M

Select PLL_F80M as the source clock

enumerator ADC_DIGI_CLK_SRC_DEFAULT

Select PLL_F80M as the default clock choice

enum soc_periph_glitch_filter_clk_src_t

Glitch filter clock source.

Values:

enumerator GLITCH_FILTER_CLK_SRC_APB

Select APB clock as the source clock

enumerator GLITCH_FILTER_CLK_SRC_DEFAULT

Select APB clock as the default clock choice

enum soc_periph_mwdt_clk_src_t

MWDT clock source.

Values:

enumerator MWDT_CLK_SRC_XTAL

Select XTAL as the source clock

enumerator MWDT_CLK_SRC_PLL_F40M

Select PLL 40 Mhz as the source clock

enumerator MWDT_CLK_SRC_DEFAULT

Select PLL 40 Mhz 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_PLL_DIV_CLK

Select PLL_F60M as the source clock

enumerator LEDC_USE_RC_FAST_CLK

Select RC_FAST as the source clock

enumerator LEDC_USE_XTAL_CLK

Select XTAL as the source clock

enumerator LEDC_USE_RTC8M_CLK

Alias of 'LEDC_USE_RC_FAST_CLK'

Header File

• components/esp_hw_support/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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