1 files changed, 47 insertions, 0 deletions

diff --git a/platforms/chibios/timer.c b/platforms/chibios/timer.c
new file mode 100644
index 000000000..9f664e1f7
--- /dev/null
+++ b/platforms/chibios/timer.c
@@ -0,0 +1,47 @@
+#include <ch.h>
+
+#include "timer.h"
+
+static uint32_t reset_point = 0;
+#if CH_CFG_ST_RESOLUTION < 32
+static uint32_t last_systime = 0;
+static uint32_t overflow     = 0;
+#endif
+
+void timer_init(void) { timer_clear(); }
+
+void timer_clear(void) {
+    reset_point = (uint32_t)chVTGetSystemTime();
+#if CH_CFG_ST_RESOLUTION < 32
+    last_systime = reset_point;
+    overflow     = 0;
+#endif
+}
+
+uint16_t timer_read(void) { return (uint16_t)timer_read32(); }
+
+uint32_t timer_read32(void) {
+    uint32_t systime = (uint32_t)chVTGetSystemTime();
+
+#if CH_CFG_ST_RESOLUTION < 32
+    // If/when we need to support 64-bit chips, this may need to be modified to match the native bit-ness of the MCU.
+    // At this point, the only SysTick resolution allowed other than 32 is 16 bit.
+    // In the 16-bit case, at:
+    //    - CH_CFG_ST_FREQUENCY = 100000, overflow will occur every ~0.65 seconds
+    //    - CH_CFG_ST_FREQUENCY = 10000, overflow will occur every ~6.5 seconds
+    //    - CH_CFG_ST_FREQUENCY = 1000, overflow will occur every ~65 seconds
+    // With this implementation, as long as we ensure a timer read happens at least once during the overflow period, timing should be accurate.
+    if (systime < last_systime) {
+        overflow += ((uint32_t)1) << CH_CFG_ST_RESOLUTION;
+    }
+
+    last_systime = systime;
+    return (uint32_t)TIME_I2MS(systime - reset_point + overflow);
+#else
+    return (uint32_t)TIME_I2MS(systime - reset_point);
+#endif
+}
+
+uint16_t timer_elapsed(uint16_t last) { return TIMER_DIFF_16(timer_read(), last); }
+
+uint32_t timer_elapsed32(uint32_t last) { return TIMER_DIFF_32(timer_read32(), last); }