Very high speed filler display from FLEX I/O

I know your problem is resolved already, but if you have so many cans passing through, wouldn't the prox switch always stay on? I figured the end of one can would be on one end of the prox while the start of the next can would be on the other end of the prox. Wouldn't a laser pointer work better?

No worries though, good job resolving the issue!

The specs for the FlexIO say the default filtering is only 0.5ms so the input should not be having much trouble getting the signal unless the duty cycle of the signal is terrible.
2300 cpm is one pulse every 26ms. Assuming your duty cycle is 50% you should be able to read the stream with a RPI of 13ms. Even compactlogix IO with their ****ty 8ms filter could do it.

I suspect the signal duration is super short. In that case you need to sample at half the duration of the signal. If you have a decent duty cycle you can get useful performance from proxes to use as ghetto encoders.