esp-idf/components/esp32s2beta/include/esp_clk.h

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2019-05-09 23:34:06 -04:00
// Copyright 2015-2017 Espressif Systems (Shanghai) PTE LTD
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.
#pragma once
/**
* @file esp_clk.h
*
* This file contains declarations of clock related functions.
*/
/**
* @brief Get the calibration value of RTC slow clock
*
* The value is in the same format as returned by rtc_clk_cal (microseconds,
* in Q13.19 fixed-point format).
*
* @return the calibration value obtained using rtc_clk_cal, at startup time
*/
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uint32_t esp_clk_slowclk_cal_get(void);
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/**
* @brief Update the calibration value of RTC slow clock
*
* The value has to be in the same format as returned by rtc_clk_cal (microseconds,
* in Q13.19 fixed-point format).
* This value is used by timekeeping functions (such as gettimeofday) to
* calculate current time based on RTC counter value.
* @param value calibration value obtained using rtc_clk_cal
*/
void esp_clk_slowclk_cal_set(uint32_t value);
/**
* @brief Return current CPU clock frequency
* When frequency switching is performed, this frequency may change.
* However it is guaranteed that the frequency never changes with a critical
* section.
*
* @return CPU clock frequency, in Hz
*/
int esp_clk_cpu_freq(void);
/**
* @brief Return current APB clock frequency
*
* When frequency switching is performed, this frequency may change.
* However it is guaranteed that the frequency never changes with a critical
* section.
*
* @return APB clock frequency, in Hz
*/
int esp_clk_apb_freq(void);
/**
* @brief Read value of RTC counter, converting it to microseconds
* @attention The value returned by this function may change abruptly when
* calibration value of RTC counter is updated via esp_clk_slowclk_cal_set
* function. This should not happen unless application calls esp_clk_slowclk_cal_set.
* In ESP-IDF, esp_clk_slowclk_cal_set is only called in startup code.
*
* @return Value or RTC counter, expressed in microseconds
*/
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uint64_t esp_clk_rtc_time(void);