I find that information regarding measurment of human pulse rate is rather limited here. So, I would like to share my method here.

Basically, an Infra-red emitting diode and a photo-diode will be used. They are connected in parallel, and a series resistor is connected to each diode.

These two diodes are shield from ambience light, leaving only two holes on the top. They are also shield from each other.

To detect the pulse, a finfer is placed over the sensor; covering the two openings. The infra-red radiation produced by the emitter falls on the finger and is reflected back towards the detector via the blood stream. The amount of radiation falling on the photodiode induces a current in it.

This forms a series of pulses, which can be fed into the INT pins of 8751.

Are there better methods in measuring pulse rate? Anyone would like to share your experiences?