Diff: hal/lp_ticker_api.h

Revision:

186:707f6e361f3e

Parent:

180:96ed750bd169

Child:

187:0387e8f68319

--- a/hal/lp_ticker_api.h	Thu Apr 19 17:12:19 2018 +0100
+++ b/hal/lp_ticker_api.h	Fri Jun 22 16:45:37 2018 +0100
@@ -21,7 +21,7 @@
 
 #include "device.h"
 
-#if DEVICE_LOWPOWERTIMER
+#if DEVICE_LPTICKER
 
 #include "hal/ticker_api.h"
 
@@ -30,10 +30,37 @@
 #endif
 
 /**
- * \defgroup hal_LpTicker Low Power Ticker Functions
+ * \defgroup hal_lp_ticker Low Power Ticker
+ * Low level interface to the low power ticker of a target
+ *
+ * # Defined behavior
+ * * Has a reported frequency between 4KHz and 64KHz - verified by ::lp_ticker_info_test
+ * * Has a counter that is at least 12 bits wide - verified by ::lp_ticker_info_test
+ * * Continues operating in deep sleep mode - verified by ::lp_ticker_deepsleep_test
+ * * All behavior defined by the @ref hal_ticker_shared "ticker specification"
+ *
+ * # Undefined behavior
+ * * See the @ref hal_ticker_shared "ticker specification"
+ * * Calling any function other than lp_ticker_init after calling lp_ticker_free
+ *
+ * # Potential bugs
+ * * Glitches due to ripple counter - Verified by ::lp_ticker_glitch_test
+ *
+ * @see hal_lp_ticker_tests
+ *
  * @{
  */
 
+/**
+ * \defgroup hal_lp_ticker_tests Low Power Ticker tests
+ * Tests to validate the proper implementation of the low power ticker
+ *
+ * To run the low power ticker hal tests use the command:
+ *
+ *     mbed test -t <toolchain> -m <target> -n tests-mbed_hal-common_ticker*,tests-mbed_hal-lp_ticker*
+ *
+ */
+
 typedef void (*ticker_irq_handler_type)(const ticker_data_t *const);
 
 /** Set low power ticker IRQ handler
@@ -42,7 +69,7 @@
  *
  * @return previous ticker IRQ handler
  *
- * @note by default IRQ handler is set to 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
  *
  */
@@ -63,39 +90,147 @@
 
 /** Initialize the low power ticker
  *
+ * Initialize or re-initialize the ticker. This resets all the
+ * clocking and prescaler registers, along with disabling
+ * the compare interrupt.
+ *
+ * Pseudo Code:
+ * @code
+ * void lp_ticker_init()
+ * {
+ *     // Enable clock gate so processor can read LPTMR registers
+ *     POWER_CTRL |= POWER_CTRL_LPTMR_Msk;
+ *
+ *     // Disable the timer and ensure it is powered down
+ *     LPTMR_CTRL &= ~(LPTMR_CTRL_ENABLE_Msk | LPTMR_CTRL_COMPARE_ENABLE_Msk);
+ *
+ *     // Configure divisors - no division necessary
+ *     LPTMR_PRESCALE = 0;
+ *     LPTMR_CTRL |= LPTMR_CTRL_ENABLE_Msk;
+ *
+ *     // Install the interrupt handler
+ *     NVIC_SetVector(LPTMR_IRQn, (uint32_t)lp_ticker_irq_handler);
+ *     NVIC_EnableIRQ(LPTMR_IRQn);
+ * }
+ * @endcode
  */
 void lp_ticker_init(void);
 
-/** Read the current counter
+/** Deinitialize the lower power ticker
+ *
+ * Powerdown the lp ticker in preparation for sleep, powerdown, or reset.
+ *
+ * After calling this function no other ticker functions should be called except
+ * lp_ticker_init(). Calling any function other than init after freeing is
+ * undefined.
+ *
+ * @note This function stops the ticker from counting.
+ */
+void lp_ticker_free(void);
+
+/** Read the current tick
+ *
+ * If no rollover has occurred, the seconds passed since lp_ticker_init()
+ * was called can be found by dividing the ticks returned by this function
+ * by the frequency returned by ::lp_ticker_get_info.
  *
- * @return The current timer's counter value in microseconds
+ * @return The current timer's counter value in ticks
+ *
+ * Pseudo Code:
+ * @code
+ * uint32_t lp_ticker_read()
+ * {
+ *     uint16_t count;
+ *     uint16_t last_count;
+ *
+ *     // Loop until the same tick is read twice since this
+ *     // is ripple counter on a different clock domain.
+ *     count = LPTMR_COUNT;
+ *     do {
+ *         last_count = count;
+ *         count = LPTMR_COUNT;
+ *     } while (last_count != count);
+ *
+ *     return count;
+ * }
+ * @endcode
  */
 uint32_t lp_ticker_read(void);
 
 /** Set interrupt for specified timestamp
  *
- * @param timestamp The time in microseconds to be set
+ * @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
+ * lp_ticker_fire_interrupt() if this is the case
+ *
+ * @note calling this function with timestamp of more than the supported
+ * number of bits returned by ::lp_ticker_get_info results in undefined
+ * behavior.
+ *
+ * Pseudo Code:
+ * @code
+ * void lp_ticker_set_interrupt(timestamp_t timestamp)
+ * {
+ *     LPTMR_COMPARE = timestamp;
+ *     LPTMR_CTRL |= LPTMR_CTRL_COMPARE_ENABLE_Msk;
+ * }
+ * @endcode
  */
 void lp_ticker_set_interrupt(timestamp_t timestamp);
 
 /** Disable low power ticker interrupt
  *
+ * Pseudo Code:
+ * @code
+ * void lp_ticker_disable_interrupt(void)
+ * {
+ *     // Disable the compare interrupt
+ *     LPTMR_CTRL &= ~LPTMR_CTRL_COMPARE_ENABLE_Msk;
+ * }
+ * @endcode
  */
 void lp_ticker_disable_interrupt(void);
 
 /** Clear the low power ticker interrupt
  *
+ * Pseudo Code:
+ * @code
+ * void lp_ticker_clear_interrupt(void)
+ * {
+ *     // Write to the ICR (interrupt clear register) of the LPTMR
+ *     LPTMR_ICR = LPTMR_ICR_COMPARE_Msk;
+ * }
+ * @endcode
  */
 void lp_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 lp_ticker_fire_interrupt(void)
+ * {
+ *     NVIC_SetPendingIRQ(LPTMR_IRQn);
+ * }
+ * @endcode
  */
 void lp_ticker_fire_interrupt(void);
 
 /** Get frequency and counter bits of this ticker.
  *
+ * Pseudo Code:
+ * @code
+ * const ticker_info_t* lp_ticker_get_info()
+ * {
+ *     static const ticker_info_t info = {
+ *         32768,      // 32KHz
+ *         16          // 16 bit counter
+ *     };
+ *     return &info;
+ * }
+ * @endcode
  */
 const ticker_info_t* lp_ticker_get_info(void);