Receiver hardware for IR beam (red eye)?

[MeindertKuipers]

Looks like an interesting state machine. I have not used IRQ's so far for syncing between state machines. Since it goes through the NVIC I had the idea that there may be an extra delay.
I use 2 extra GPIO's for this type of syncing, but then I have one source, and multiple state machines that need to sync to that one.