Control Usb Relay

Control USB relay modules with on/off switching, state tracking, and automation support.

When to Use

User wants to control a USB relay module to switch devices on/off or automate based on sensor input.

Core Rules

1. Verify Hardware First — Confirm relay is at /dev/ttyUSB1 and user is in dialout group.

2. Always Initialize — Call relay.connect() before any control. Wait 500ms for connection.

3. Use Correct Protocol — ON: A0 01 01 A2, OFF: A0 01 00 A1. Different modules may use different protocols.

4. State May Drift — get_status() tracks last command. May differ if manual override occurred.

5. Disconnect on Exit — Always call relay.disconnect() to release serial port.

Data Storage

No persistent storage. Relay state tracked in memory during session only.

External Endpoints

Endpoint	Purpose
/dev/ttyUSB1	Serial control

Quick Reference

Topic	File
Setup & examples	setup.md
Troubleshooting	setup.md

Security Notes

• Physical device control — confirm with user before switching
• Some relays need external 5V/12V power supply