--- /dev/null
+#include "cmsis.h"
+#include "timer.h"
+
+/* Mill second tick count */
+volatile uint32_t timer_count = 0;
+
+/* Timer interrupt handler */
+void SysTick_Handler(void) {
+ timer_count++;
+}
+
+void timer_init(void)
+{
+ SysTick_Config(SystemCoreClock / 1000); /* 1ms tick */
+}
+
+void timer_clear(void)
+{
+ timer_count = 0;
+}
+
+uint16_t timer_read(void)
+{
+ return (uint16_t)(timer_count & 0xFFFF);
+}
+
+uint32_t timer_read32(void)
+{
+ return timer_count;
+}
+
+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);
+}