tool/mbed/mbed-sdk/libraries/mbed/targets/hal/TARGET_Maxim/TARGET_MAX32610/us_ticker.c

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  33
  34 #include "mbed_error.h"
  35 #include "us_ticker_api.h"
  36 #include "PeripheralNames.h"
  37 #include "tmr_regs.h"
  38
  39 #define US_TIMER        MXC_TMR0
  40 #define US_TIMER_IRQn   TMR0_IRQn
  41
  42 static int us_ticker_inited = 0;
  43 static uint32_t ticks_per_us;
  44 static uint32_t tick_win;
  45 static volatile uint64_t current_cnt;   // Hold the current ticks
  46 static volatile uint64_t event_cnt;     // Holds the value of the next event
  47
  48 #define ticks_to_us(ticks)  ((ticks) / ticks_per_us);
  49 #define MAX_TICK_VAL    ((uint64_t)0xFFFFFFFF * ticks_per_us)
  50
  51 //******************************************************************************
  52 static inline void inc_current_cnt(uint32_t inc) {
  53
  54     // Overflow the ticker when the us ticker overflows
  55     current_cnt += inc;
  56     if(current_cnt > MAX_TICK_VAL) {
  57         current_cnt -= (MAX_TICK_VAL + 1);
  58     }
  59 }
  60
  61 //******************************************************************************
  62 static inline int event_passed(uint64_t current, uint64_t event) {
  63
  64     // Determine if the event has already happened.
  65     // If the event is behind the current ticker, within a window,
  66     // then the event has already happened.
  67     if(((current < tick_win) && ((event < current) ||
  68         (event > (MAX_TICK_VAL - (tick_win - current))))) ||
  69         ((event < current) && (event > (current - tick_win)))) {
  70         return 1;
  71     }
  72
  73     return 0;
  74 }
  75
  76 //******************************************************************************
  77 static inline uint64_t event_diff(uint64_t current, uint64_t event) {
  78
  79     // Check to see if the ticker will overflow before the event
  80     if(current <= event) {
  81         return (event - current);
  82     }
  83
  84     return ((MAX_TICK_VAL - current) + event);
  85 }
  86
  87 //******************************************************************************
  88 static void tmr_handler(void)
  89 {
  90     uint32_t term_cnt32 = US_TIMER->term_cnt32;
  91     US_TIMER->term_cnt32 = 0xFFFFFFFF;  // reset to max value to prevent further interrupts
  92     US_TIMER->intfl = (MXC_F_TMR_INTFL_TIMER0 | MXC_F_TMR_INTFL_TIMER1);    // clear interrupt
  93     NVIC_ClearPendingIRQ(US_TIMER_IRQn);
  94
  95     inc_current_cnt(term_cnt32);
  96
  97     if (event_passed(current_cnt + US_TIMER->count32, event_cnt )) {
  98         // the timestamp has expired
  99         event_cnt = 0xFFFFFFFFFFFFFFFFULL;  // reset to max value
 100         us_ticker_irq_handler();
 101     } else {
 102
 103         uint64_t diff = event_diff(current_cnt, event_cnt);
 104         if (diff < (uint64_t)0xFFFFFFFF) {
 105             // the event occurs before the next overflow
 106             US_TIMER->term_cnt32 = diff;
 107
 108             // Since the timer keeps counting after the terminal value is reached, it is possible that the new
 109             // terminal value is in the past.
 110             if (US_TIMER->term_cnt32 < US_TIMER->count32) {
 111                 // the timestamp has expired
 112                 US_TIMER->term_cnt32 = 0xFFFFFFFF;  // reset to max value to prevent further interrupts
 113                 US_TIMER->intfl = (MXC_F_TMR_INTFL_TIMER0 | MXC_F_TMR_INTFL_TIMER1);    // clear interrupt
 114                 NVIC_ClearPendingIRQ(US_TIMER_IRQn);
 115                 event_cnt = 0xFFFFFFFFFFFFFFFFULL;  // reset to max value
 116                 us_ticker_irq_handler();
 117             }
 118         }
 119     }
 120 }
 121
 122 //******************************************************************************
 123 void us_ticker_init(void)
 124 {
 125     if (us_ticker_inited)
 126         return;
 127     us_ticker_inited = 1;
 128
 129     current_cnt = 0;
 130     event_cnt = 0xFFFFFFFFFFFFFFFFULL;  // reset to max value
 131
 132     if (SystemCoreClock <= 1000000) {
 133         error("us_ticker cannot operate at this SystemCoreClock");
 134         return;
 135     }
 136
 137     // Configure timer for 32-bit continuous mode with /1 prescaler
 138     US_TIMER->ctrl = MXC_E_TMR_MODE_CONTINUOUS << MXC_F_TMR_CTRL_MODE_POS | (0 << MXC_F_TMR_CTRL_PRESCALE_POS);
 139     ticks_per_us = SystemCoreClock / 1000000;
 140
 141     // Set the tick window to 10ms
 142     tick_win = SystemCoreClock/100;
 143
 144     // Set timer overflow to the max
 145     US_TIMER->term_cnt32 = 0xFFFFFFFF;
 146     US_TIMER->pwm_cap32 = 0xFFFFFFFF;
 147     US_TIMER->count32 = 0;
 148
 149     US_TIMER->intfl = (MXC_F_TMR_INTFL_TIMER0 | MXC_F_TMR_INTFL_TIMER1);    // clear pending interrupts
 150
 151     NVIC_SetVector(US_TIMER_IRQn, (uint32_t)tmr_handler);
 152     NVIC_EnableIRQ(US_TIMER_IRQn);
 153
 154     US_TIMER->inten |= MXC_F_TMR_INTEN_TIMER0;  // enable interrupts
 155     US_TIMER->ctrl |= MXC_F_TMR_CTRL_ENABLE0;   // enable timer
 156 }
 157
 158 //******************************************************************************
 159 void us_ticker_deinit(void)
 160 {
 161     US_TIMER->ctrl = 0;     // disable timer
 162     US_TIMER->inten = 0;    // disable interrupts
 163     US_TIMER->intfl = (MXC_F_TMR_INTFL_TIMER0 | MXC_F_TMR_INTFL_TIMER1);    // clear interrupts
 164     us_ticker_inited = 0;
 165 }
 166
 167 //******************************************************************************
 168 uint32_t us_ticker_read(void)
 169 {
 170     uint64_t current_cnt1, current_cnt2;
 171     uint32_t term_cnt, tmr_cnt;
 172     int intfl1, intfl2;
 173
 174     if (!us_ticker_inited)
 175         us_ticker_init();
 176
 177     // Ensure coherency between current_cnt and US_TIMER->count32
 178     do {
 179         current_cnt1 = current_cnt;
 180         intfl1 = US_TIMER->intfl;
 181         term_cnt = US_TIMER->term_cnt32;
 182         tmr_cnt = US_TIMER->count32;
 183         intfl2 = US_TIMER->intfl;
 184         current_cnt2 = current_cnt;
 185     } while ((current_cnt1 != current_cnt2) || (intfl1 != intfl2));
 186
 187     if (intfl1) {
 188         current_cnt1 += term_cnt;
 189     }
 190
 191     current_cnt1 += tmr_cnt;
 192
 193     return (current_cnt1 / ticks_per_us);
 194 }
 195
 196 //******************************************************************************
 197 void us_ticker_set_interrupt(timestamp_t timestamp)
 198 {
 199     // Note: interrupts are disabled before this function is called.
 200     US_TIMER->ctrl &= ~MXC_F_TMR_CTRL_ENABLE0;  // disable timer
 201
 202     if (US_TIMER->intfl) {
 203         US_TIMER->intfl = (MXC_F_TMR_INTFL_TIMER0 | MXC_F_TMR_INTFL_TIMER1);    // clear interrupt
 204         NVIC_ClearPendingIRQ(US_TIMER_IRQn);
 205         inc_current_cnt(US_TIMER->term_cnt32);
 206     }
 207
 208     // add and reset the current count value
 209     inc_current_cnt(US_TIMER->count32);
 210     US_TIMER->count32 = 0;
 211
 212     // add the number of cycles that the timer is disabled here for
 213     inc_current_cnt(200);
 214
 215     event_cnt = (uint64_t)timestamp * ticks_per_us;
 216
 217     // Check to see if the event has already passed
 218     if (!event_passed(current_cnt, event_cnt)) {
 219         uint64_t diff = event_diff(current_cnt, event_cnt);
 220         if (diff < (uint64_t)0xFFFFFFFF) {
 221             // the event occurs before the next overflow
 222             US_TIMER->term_cnt32 = diff;
 223         } else {
 224             // the event occurs after the next overflow
 225             US_TIMER->term_cnt32 = 0xFFFFFFFF;  // set to max
 226         }
 227     } else {
 228         // the requested timestamp occurs in the past
 229         // set the timer up to immediately expire
 230         US_TIMER->term_cnt32 = 1;
 231     }
 232     US_TIMER->ctrl |= MXC_F_TMR_CTRL_ENABLE0;   // enable timer
 233 }
 234
 235 //******************************************************************************
 236 void us_ticker_disable_interrupt(void)
 237 {
 238     // There are no more events, set timer overflow to the max
 239     US_TIMER->term_cnt32 = 0xFFFFFFFF;
 240 }
 241
 242 //******************************************************************************
 243 void us_ticker_clear_interrupt(void)
 244 {
 245     // cleared in the local handler
 246 }
 247
 248 //******************************************************************************
 249 void us_ticker_set(timestamp_t timestamp)
 250 {
 251     US_TIMER->ctrl &= ~MXC_F_TMR_CTRL_ENABLE0;  // disable timer
 252     current_cnt = (uint64_t)timestamp * ticks_per_us;
 253     US_TIMER->count32 = 0;
 254     US_TIMER->term_cnt32 = 0xFFFFFFFF;
 255     US_TIMER->ctrl |= MXC_F_TMR_CTRL_ENABLE0;   // enable timer
 256
 257     if (((uint64_t)timestamp * ticks_per_us) >= event_cnt) {
 258         // The next timestamp has elapsed. Trigger the interrupt to handle it.
 259         NVIC_SetPendingIRQ(US_TIMER_IRQn);
 260     }
 261 }