SHARP_UNIT
#define SHARP_BIT_PULSE (8 * SHARP_UNIT) /* 320us */
#define SHARP_BIT_0_PERIOD (25 * SHARP_UNIT) /* 1ms (680us space) */
#define SHARP_BIT_1_PERIOD (50 * SHARP_UNIT) /* 2ms (1680us space) */
#define SHARP_BIT_0_SPACE (17 * SHARP_UNIT) /* 680us space */
#define SHARP_BIT_1_SPACE (42 * SHARP_UNIT) /* 1680us space */
#define SHARP_ECHO_SPACE (1000 * SHARP_UNIT) /* 40 ms */
#define SHARP_TRAILER_SPACE (125 * SHARP_UNIT) /* 5 ms (even longer) */