add time

Core/Src/time.c

@@ -0,0 +1,16 @@
+#include <stdint.h>
+#include "time.h"
+#include "main.h"
+
+int32_t ticks_ms() {
+    return HAL_GetTick() & INT32_MAX;
+}
+
+int32_t ticks_add(int32_t t1, int32_t delta) {
+    return (t1 + delta) & INT32_MAX;
+}
+
+int32_t ticks_diff(int32_t t1, int32_t t2) {
+    int32_t half = (INT32_MAX / 2) + 1;
+    return ((t1 - t2 + half) & INT32_MAX) - half;
+}