Running it a frustrating problem. When connecting common ground between Arduino and power supply serial communication is lost. TX(4) pin goes to >4V while RX(3) goes to <0.5V. FYI I am using software serial on a Arduino Nano.
The circuit contains the following components.
- 14V 30A DC Switching Power Supply (PYRAMID PSV-300)
- ECUMASTER EMU (Communication is based on RS232 at 19200. Output levels are <5V)
- DC-DC Buck Convertor 12V to 5V. (POLOLU D36V6F5, Also tested with POLOLU D24V22F5)
- Arduino Nano
- CANBUS Module (Not Shown, Issue is still present with this completely removed)
I have posted some hand drawn schematics to illustrate what wiring worked and what wiring didn’t work.
Troubleshooting that has been completed so far.
- If the Arduino Nano is powered via Laptop/Wall wart serial communication works as intended.
- The moment I bridge the GND from Arduino to Power Supply serial communication stops working.
- Having the Arduino Nano powered via +5V port using a 5V regulator serial communication does not working.
- Having the Arduino Nano powered via USB port using a 5V regulator Serial communication does not work.
This circuit is to be installed within a vehicle where the grounds are common hence would like to figure out why serial communication stops working when grounds are common.