How to prevent interference in I/O module DI/DO cabling?

Improving the immunity of I/O module DI/DO wiring requires a comprehensive approach to routing strategies and termination techniques. DI signal lines should be as short as possible and kept away from noise sources such as clocks and power supplies. Using differential pair routing, maintaining equal length and spacing, can effectively suppress common-mode interference. Connect a small capacitor in parallel to ground at the receiving end, forming a low-pass filter with the line impedance matching resistor. For long DI lines, add a resistor of several tens of ohms in series at the entry point to dampen reflections, and use a TVS diode array such as ESDSVLC05-4 for protection.

For DO wiring, especially when driving inductive loads, output lines should be kept away from other sensitive lines and, where possible, use twisted-pair cables. Connect a small resistor or ferrite bead in series at the output of the driver chip to slow down switching edges and reduce high-frequency radiation. Add freewheeling diodes to relay or transistor outputs and place them close to the load. All DI/DO lines should reference a complete ground plane to ensure a continuous return path. At connectors, DI/DO signal pins should be surrounded by ground pins. Verify the immunity of the wiring, especially its resistance to EFT and ESD, through simulation and testing.