Setting up our hardware

The first thing we are going to do is to set up our pieces of hardware so that the Pi Zero can communicate with each piece correctly. The Pulse Sensor Amped is a 5V analog device designed for use with the Arduino products. Arduino boards have a builtin Analog to Digital Converter (ADC), which allows you to connect analog sensors and monitor them digitally. The Pi Zero does not have an ADC; this is where the Enviro pHAT comes in. We will use the ADC of the Enviro pHAT to connect our analog heart rate sensor to our Pi Zero and finally use the Scroll pHAT HD as our display system. There is one more problem, which we need to solve with this sensor; the problem is that it's output is at 5V and our Pi Zero and the Enviro pHAT wants the input at 3.3V. To achieve this, we are going to use a simple resistor-based voltage divider. We are going to use 3 x 330...