Reduce display startup time

Core/Src/shorttimer.c

@@ -0,0 +1,29 @@
+#include "shorttimer.h"
+
+#include "stm32h7xx_hal.h"
+#include "stm32h7xx_hal_tim.h"
+#include <stdint.h>
+
+static TIM_HandleTypeDef *htim;
+static uint32_t ticks;
+
+void shorttimer_init(TIM_HandleTypeDef *handle) {
+  htim = handle;
+  ticks = 0;
+  HAL_TIM_Base_Start_IT(htim);
+}
+
+uint32_t shorttimer_gettick(void) { return ticks; }
+
+void shorttimer_sleep(uint32_t microseconds) {
+  volatile uint32_t start = shorttimer_gettick();
+  // Add another tick to guarantee a minimum wait
+  if (microseconds < UINT32_MAX) {
+    microseconds++;
+  }
+
+  while (shorttimer_gettick() - start < microseconds) {
+  }
+}
+
+void shorttimer_callback() { ticks++; }