Improve README and doxygen comments

include/sta/hal/delay.hpp

@@ -3,10 +3,10 @@
  *
  * Configuration:
  *     STA_HAL_DELAY_ENABLE: Enable module
- *     STA_HAL_DELAY_US_TIM: HAL TIM instance for `delayUs()`
+ *     STA_HAL_DELAY_US_TIM: 1 MHz TIM instance used by `sta::delayUs`
  *
- * NOTE: Don't forget to start TIM. When using startup system task this
- *       is automatically handled.
+ * NOTE: TIM time base must be started before use of `sta::delayUs` by calling `sta::initHAL`.
+ *       When using startup system task this is handled automatically.
  */
 #ifndef STA_HAL_DELAY_HPP
 #define STA_HAL_DELAY_HPP
@@ -14,6 +14,8 @@
 #include <sta/config.hpp>
 #ifdef STA_HAL_DELAY_ENABLE
 
+#include <cstdint>
+
 
 namespace sta
 {