In this video, I walk through a complete, real-world example of building a custom Modbus  TCP/IP server device from the ground up - from programming in Arduino and connecting the wires, to seeing live values and overriding equipment on a BAS or SCADA screen. All for under $20. Contents Introduction Key Concepts & Takeaways Objective Memory Map Hardware Used Arduino Sketch Code Introduction Providing two paths, using both an ESP32 and Raspberry Pi, I interface with an SHT41 t