src/lib/HWTIMER/hwTimer.h

   1 #pragma once
   2
   3 #include "targets.h"
   4 #include <stdio.h>
   5
   6 #if defined(TARGET_TX)
   7 #define TimerIntervalUSDefault 4000
   8 #else
   9 #define TimerIntervalUSDefault 20000
  10 #endif
  11
  12 /**
  13  * @brief Hardware abstraction for the hardware timer to provide precise timing
  14  *
  15  * The timer provides callback for "tick" and "tock" alternating at half the update
  16  * interval each.
  17  *
  18  * The timer includes a built-in frequency offset to adjust for differences in actual
  19  * timing rates between 2 timers. The offset can be incremented, decremented or reset
  20  * to 0.
  21  *
  22  * The `phaseShift` function can be used to provide a one-time adjustment to shift the
  23  * phase of the timer so two timers can be aligned on their tock phase.
  24  */
  25 class hwTimer
  26 {
  27 public:
  28     /**
  29      * @brief Initialise the timer with the specified tick/tock callback functions.
  30      *
  31      * Only the tock callback is used for transmitter targets.
  32      *
  33      * The timer initialised in the stopped state and must be started with resume().
  34      */
  35     static void init(void (*callbackTick)(), void (*callbackTock)());
  36
  37     /**
  38      * @brief Stop the timer.
  39      *
  40      * The timer is stopped and no more callbacks are performed.
  41      */
  42     static void stop();
  43
  44     /**
  45      * @brief Resume the timer.
  46      *
  47      * The timer is started from this instant, callbacks will be called.
  48      * The timer fires a tock callback immediately after it is resumed.
  49      */
  50     static void resume();
  51
  52     /**
  53      * @brief Change the interval between callbacks.
  54      * The time between tick and tock is half the provided interval.
  55      * The timer should not be running when updateInterval() is called.
  56      *
  57      * @param time in microseconds for a full tick/tock.
  58      */
  59     static void updateInterval(uint32_t time = TimerIntervalUSDefault);
  60     /**
  61      * @brief Reset the frequency offset to zero microseconds
  62      */
  63     static ICACHE_RAM_ATTR void inline resetFreqOffset() { FreqOffset = 0; }
  64
  65     /**
  66      * @brief Increment the frequency offset by one microsecond
  67      */
  68     static ICACHE_RAM_ATTR void inline incFreqOffset() { FreqOffset++; }
  69
  70
  71     /**
  72      * @brief Decrement the frequency offset by one microsecond
  73      */
  74     static ICACHE_RAM_ATTR void inline decFreqOffset() { FreqOffset--; }
  75
  76     /**
  77      * @brief Get the frequency offset
  78      */
  79     static ICACHE_RAM_ATTR int32_t inline getFreqOffset() { return FreqOffset; }
  80
  81     /**
  82      * @brief Provides a coarse one time adjustment to the frequency to
  83      * align the phase of two timers.
  84      *
  85      * The phase shift is a delay that is added to the timer after the
  86      * next tock callback, delaying the tick after by phaseShift microseonds.
  87      *
  88      * The maximum phase shift is 1/4 of the update interval.
  89      *
  90      * @param newPhaseShift time in microseconds to delay the timer.
  91      */
  92     static void phaseShift(int32_t newPhaseShift);
  93
  94     static volatile bool running;
  95     static volatile bool isTick;
  96
  97 private:
  98     static void callback();
  99
 100     static void (*callbackTick)();
 101     static void (*callbackTock)();
 102
 103     static volatile uint32_t HWtimerInterval;
 104     static volatile int32_t PhaseShift;
 105     static volatile int32_t FreqOffset;
 106 };