So let’s say your using an Arduino in your project. You already have the hardware-based serial interface working with one portion of the project and need a second serial port for unrelated hardware.

Before opening the Arduino software, wire up the Arduino according to the circuits page using the 8MHz minimalist breadboard circuit but with a 10k pull-up resistor on the reset pin (physical pin 1).

I am currently using a PZEM-004T V4.0 100A connected to an Arduino Uno. I have connected the 5V and Gnd from the Arduino to the PZEM. I used the software serial example. PZEM TX is connected to pin 12 ...