Level shifter to Interface Microcontroller A/D channel
Something simple like this should make it easy enough to count the pulses:







simulate this circuit &ndash; Schematic created using CircuitLab

So the idea is to rectify the pulse, feed it into a Schmitt Trigger and the use an interrupt on the micro controller to count the pulses. In the schematic there is an inverting not gate. This is meant to be representative of a 74HC14 hex inverting Schmitt trigger. These are very cheap and very common. The inversion makes no difference to the solution since the interrupt on the micro controller will trigger on a HIGH to LOW instead of a LOW to HIGH.

Since the voltage swing is potentially small, you may want to consider using a Schottky diode to reduce the effect of the diodes forward voltage. Also make sure that the rectified voltage is enough to trigger the Schmitt Trigger.

EDIT: For this to work, you would need to remove the DC bias from the signal by adding a capacitor in series with the diode.