SuperDroid Robots Dual LS7366R Quadrature Encoder Buffer

This board does what it says, and it does it well. It's kind of pricey in my opinion, but if you absolutely positively cannot miss a pulse on either of two axes, it's the way to go. (It has a minimum quadrature period of around 52ns or so, meaning you could hypothetically read something like 24000 revolutions per second on a 200PPR encoder? Works for me!) No more fussing with Arduino hardware or pin-change interrupts. Honestly, the only thing that annoys me about the LS7366R is that it expects the index signal to be inverted, i.e. active-low (which none of my US Digital encoders do), and you cannot configure it in software (unlike the LS7366, which lets you set either a negative or positive index in MDR0 bit 6). Still, that's not SuperDroid's fault - this board does exactly what it's supposed to do - and it's not really a pain for me to throw an inverter into the circuit. Don't forget -- if you need a simultaneous reading of both axes, activate both SS lines at the same time and send a 'copy CNTR to OTR' command to lock in the values on both devices, then read each OTR value at your leisure. These chips will do SPI at over 4MHz but that's still too slow to read one buffer and then the other buffer.

Works great, but at almost $50 is a little overpriced for what you get. It doesn't even come with headers/connectors. I will say that superdroids has great documentation on it.