Diff: mbed-os/hal/us_ticker_api.h

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+++ b/mbed-os/hal/us_ticker_api.h	Thu Jun 21 13:51:43 2018 +0000
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+
+/** \addtogroup hal */
+/** @{*/
+/* mbed Microcontroller Library
+ * Copyright (c) 2006-2015 ARM Limited
+ *
+ * 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.
+ */
+#ifndef MBED_US_TICKER_API_H
+#define MBED_US_TICKER_API_H
+
+#include <stdint.h>
+#include "hal/ticker_api.h"
+
+#ifdef __cplusplus
+extern "C" {
+#endif
+
+/**
+ * \defgroup hal_us_ticker Microsecond Ticker
+ * Low level interface to the microsecond ticker of a target
+ *
+ * # Defined behavior
+ * * Has a reported frequency between 250KHz and 8MHz - Verified by test ::us_ticker_info_test
+ * * Has a counter that is at least 16 bits wide - Verified by test ::us_ticker_info_test
+ * * All behavior defined by the @ref hal_ticker_shared "ticker specification"
+ *
+ * # Undefined behavior
+ * * See the @ref hal_ticker_shared "ticker specification"
+ *
+ * @see hal_us_ticker_tests
+ *
+ * @{
+ */
+
+/**
+ * \defgroup hal_us_ticker_tests Microsecond Ticker tests
+ * Tests to validate the proper implementation of the microsecond ticker
+ *
+ * To run the microsecond ticker hal tests use the command:
+ *
+ *     mbed test -t <toolchain> -m <target> -n tests-mbed_hal-common_ticker*,tests-mbed_hal-us_ticker*
+ *
+ * @see hal_ticker_tests
+ *
+ */
+
+/**
+ * \defgroup hal_ticker_shared Ticker Hal
+ * Low level interface to the ticker of a target
+ *
+ * # Defined behavior
+ * * The function ticker_init is safe to call repeatedly - Verified by test ::ticker_init_test
+ * * The function ticker_init allows the ticker to keep counting and disables the ticker interrupt - Verified by test ::ticker_init_test
+ * * Ticker frequency is non-zero and counter is at least 8 bits - Verified by ::ticker_info_test
+ * * The ticker rolls over at (1 << bits) and continues counting starting from 0 - Verified by ::ticker_overflow_test
+ * * The ticker counts at the specified frequency +- 10% - Verified by ::ticker_frequency_test
+ * * The ticker increments by 1 each tick - Verified by ::ticker_increment_test
+ * * The ticker interrupt fires only when the ticker times increments to or past the value set by ticker_set_interrupt.
+ * Verified by ::ticker_interrupt_test and ::ticker_past_test
+ * * It is safe to call ticker_set_interrupt repeatedly before the handler is called - Verified by ::ticker_repeat_reschedule_test
+ * * The function ticker_fire_interrupt causes ticker_irq_handler to be called immediately from interrupt context -
+ * Verified by ::ticker_fire_now_test
+ * * The ticker operations ticker_read, ticker_clear_interrupt, ticker_set_interrupt and ticker_fire_interrupt
+ * take less than 20us to complete - Verified by ::ticker_speed_test
+ *
+ * # Undefined behavior
+ * * Calling any function other than ticker_init before the initialization of the ticker
+ * * Whether ticker_irq_handler is called a second time if the time wraps and matches the value set by ticker_set_interrupt again
+ * * Calling ticker_set_interrupt with a value that has more than the supported number of bits
+ * * Calling any function other than us_ticker_init after calling us_ticker_free
+ *
+ * # Potential bugs
+ * * Drift due to reschedule - Verified by ::ticker_repeat_reschedule_test
+ * * Incorrect overflow handling of timers - Verified by ::ticker_overflow_test
+ * * Interrupting at a time of 0 - Verified by ::ticker_overflow_test
+ * * Interrupt triggered more than once - Verified by ::ticker_interrupt_test
+ *
+ * @ingroup hal_us_ticker
+ * @ingroup hal_lp_ticker
+ */
+
+/**
+ * \defgroup hal_ticker_tests Ticker Tests
+ * Tests to validate the proper implementation of a ticker
+ *
+ * To run the ticker hal tests use the command:
+ *
+ *     mbed test -t <toolchain> -m <target> -n tests-mbed_hal-common_ticker*
+ *
+ * @ingroup hal_us_ticker
+ * @ingroup hal_lp_ticker
+ */
+
+ 
+typedef void (*ticker_irq_handler_type)(const ticker_data_t *const);
+
+/** Set ticker IRQ handler
+ *
+ * @param ticker_irq_handler IRQ handler to be connected
+ *
+ * @return previous ticker IRQ handler
+ *
+ * @note by default IRQ handler is set to ::ticker_irq_handler
+ * @note this function is primarily for testing purposes and it's not required part of HAL implementation
+ *
+ */
+ticker_irq_handler_type set_us_ticker_irq_handler(ticker_irq_handler_type ticker_irq_handler);
+
+/** Get ticker's data
+ *
+ * @return The microsecond ticker data
+ */
+const ticker_data_t* get_us_ticker_data(void);
+
+
+/** The wrapper for ticker_irq_handler, to pass us ticker's data
+ *
+ */
+void us_ticker_irq_handler(void);
+
+/* HAL us ticker */
+
+/** Initialize the ticker
+ *
+ * Initialize or re-initialize the ticker. This resets all the
+ * clocking and prescaler registers, along with disabling
+ * the compare interrupt.
+ *
+ * @note Initialization properties tested by ::ticker_init_test
+ *
+ * Pseudo Code:
+ * @code
+ * void us_ticker_init()
+ * {
+ *     // Enable clock gate so processor can read TIMER registers
+ *     POWER_CTRL |= POWER_CTRL_TIMER_Msk;
+ *
+ *     // Disable the timer and ensure it is powered down
+ *     TIMER_CTRL &= ~(TIMER_CTRL_ENABLE_Msk | TIMER_CTRL_COMPARE_ENABLE_Msk);
+ *
+ *     // Configure divisors
+ *     uint32_t prescale = SystemCoreClock / 1000000;
+ *     TIMER_PRESCALE = prescale - 1;
+ *     TIMER_CTRL |= TIMER_CTRL_ENABLE_Msk;
+ *
+ *     // Install the interrupt handler
+ *     NVIC_SetVector(TIMER_IRQn, (uint32_t)us_ticker_irq_handler);
+ *     NVIC_EnableIRQ(TIMER_IRQn);
+ * }
+ * @endcode
+ */
+void us_ticker_init(void);
+
+/** Deinitialize the us ticker
+ *
+ * Powerdown the us ticker in preparation for sleep, powerdown, or reset.
+ *
+ * After this function is called, no other ticker functions should be called
+ * except us_ticker_init(), calling any function other than init is undefined.
+ *
+ * @note This function stops the ticker from counting.
+ */
+void us_ticker_free(void);
+
+/** Read the current counter
+ *
+ * Read the current counter value without performing frequency conversions.
+ * If no rollover has occurred, the seconds passed since us_ticker_init()
+ * was called can be found by dividing the ticks returned by this function
+ * by the frequency returned by ::us_ticker_get_info.
+ *
+ * @return The current timer's counter value in ticks
+ *
+ * Pseudo Code:
+ * @code
+ * uint32_t us_ticker_read()
+ * {
+ *     return TIMER_COUNT;
+ * }
+ * @endcode
+ */
+uint32_t us_ticker_read(void);
+
+/** Set interrupt for specified timestamp
+ *
+ * @param timestamp The time in ticks to be set
+ *
+ * @note no special handling needs to be done for times in the past
+ * as the common timer code will detect this and call
+ * us_ticker_fire_interrupt() if this is the case
+ *
+ * @note calling this function with timestamp of more than the supported
+ * number of bits returned by ::us_ticker_get_info results in undefined
+ * behavior.
+ *
+ * Pseudo Code:
+ * @code
+ * void us_ticker_set_interrupt(timestamp_t timestamp)
+ * {
+ *     TIMER_COMPARE = timestamp;
+ *     TIMER_CTRL |= TIMER_CTRL_COMPARE_ENABLE_Msk;
+ * }
+ * @endcode
+ */
+void us_ticker_set_interrupt(timestamp_t timestamp);
+
+/** Disable us ticker interrupt
+ *
+ * Pseudo Code:
+ * @code
+ * void us_ticker_disable_interrupt(void)
+ * {
+ *     // Disable the compare interrupt
+ *     TIMER_CTRL &= ~TIMER_CTRL_COMPARE_ENABLE_Msk;
+ * }
+ * @endcode
+ */
+void us_ticker_disable_interrupt(void);
+
+/** Clear us ticker interrupt
+ *
+ * Pseudo Code:
+ * @code
+ * void us_ticker_clear_interrupt(void)
+ * {
+ *     // Write to the ICR (interrupt clear register) of the TIMER
+ *     TIMER_ICR = TIMER_ICR_COMPARE_Msk;
+ * }
+ * @endcode
+ */
+void us_ticker_clear_interrupt(void);
+
+/** Set pending interrupt that should be fired right away.
+ *
+ * The ticker should be initialized prior calling this function.
+ *
+ * Pseudo Code:
+ * @code
+ * void us_ticker_fire_interrupt(void)
+ * {
+ *     NVIC_SetPendingIRQ(TIMER_IRQn);
+ * }
+ * @endcode
+ */
+void us_ticker_fire_interrupt(void);
+
+/** Get frequency and counter bits of this ticker.
+ *
+ * Pseudo Code:
+ * @code
+ * const ticker_info_t* us_ticker_get_info()
+ * {
+ *     static const ticker_info_t info = {
+ *         1000000,    // 1 MHz
+ *         32          // 32 bit counter
+ *     };
+ *     return &info;
+ * }
+ * @endcode
+ */
+const ticker_info_t* us_ticker_get_info(void);
+
+/**@}*/
+
+#ifdef __cplusplus
+}
+#endif
+
+#endif
+
+/** @}*/