I went through and interesting article here

 

Basically, what they state is that once you got the correspondence between biosignal ADC reading and maximum blood pressure, you can determine systolic and diastolic pressure by applying a linear equation on the minimum and maximum ADC reading for each heart beat

 

So I have a very simple (yet not optimal) solution to the problem of determining the systolic and diastolic pressure

The flow chart of the process for measuring blood pressure is as follow

 

17 - Blood pressure measurement.png