tmk_core/common/chibios/timer.c

   1 #include "ch.h"
   2
   3 #include "timer.h"
   4
   5 static uint32_t reset_point = 0;
   6 #if CH_CFG_ST_RESOLUTION < 32
   7 static uint32_t last_systime = 0;
   8 static uint32_t overflow     = 0;
   9 #endif
  10
  11 void timer_init(void) { timer_clear(); }
  12
  13 void timer_clear(void) {
  14     reset_point = (uint32_t)chVTGetSystemTime();
  15 #if CH_CFG_ST_RESOLUTION < 32
  16     last_systime = reset_point;
  17     overflow     = 0;
  18 #endif
  19 }
  20
  21 uint16_t timer_read(void) { return (uint16_t)timer_read32(); }
  22
  23 uint32_t timer_read32(void) {
  24     uint32_t systime = (uint32_t)chVTGetSystemTime();
  25
  26 #if CH_CFG_ST_RESOLUTION < 32
  27     // If/when we need to support 64-bit chips, this may need to be modified to match the native bit-ness of the MCU.
  28     // At this point, the only SysTick resolution allowed other than 32 is 16 bit.
  29     // In the 16-bit case, at:
  30     //    - CH_CFG_ST_FREQUENCY = 100000, overflow will occur every ~0.65 seconds
  31     //    - CH_CFG_ST_FREQUENCY = 10000, overflow will occur every ~6.5 seconds
  32     //    - CH_CFG_ST_FREQUENCY = 1000, overflow will occur every ~65 seconds
  33     // With this implementation, as long as we ensure a timer read happens at least once during the overflow period, timing should be accurate.
  34     if (systime < last_systime) {
  35         overflow += ((uint32_t)1) << CH_CFG_ST_RESOLUTION;
  36     }
  37
  38     last_systime = systime;
  39     return (uint32_t)TIME_I2MS(systime - reset_point + overflow);
  40 #else
  41     return (uint32_t)TIME_I2MS(systime - reset_point);
  42 #endif
  43 }
  44
  45 uint16_t timer_elapsed(uint16_t last) { return TIMER_DIFF_16(timer_read(), last); }
  46
  47 uint32_t timer_elapsed32(uint32_t last) { return TIMER_DIFF_32(timer_read32(), last); }