+ static enum {
+ INIT,
+ START,
+ BIT0, BIT1, BIT2, BIT3, BIT4, BIT5, BIT6, BIT7,
+ PARITY,
+ STOP,
+ } state = INIT;
+ static uint8_t data = 0;
+ static uint8_t parity = 1;
+
+ // TODO: abort if elapse 100us from previous interrupt
+
+ // return unless falling edge
+ if (clock_in()) {
+ goto RETURN;
+ }