relay-usb

The relay-usb driver switches the channels of a CH340-based USB relay board, the kind that shows up on the bench as a USB serial port. Use it to press a DUT's buttons, cut its power, or drive a test point.

Property	Value
kind	relay-usb
Interfaces	relay
location	The board's /dev/serial/by-id/ path

Example

button_relay:
  kind: relay-usb
  name: "USB Relay for Buttons"
  description: "Drives the DUT's front-panel buttons"
  location: /dev/serial/by-id/usb-1a86_USB_Serial-if00-port0
  interfaces:
    - type: relay
      channel: 0
      config:
        channels:
          - { number: 1, name: "Power button" }
          - { number: 2, name: "User button" }
          - { number: 3, name: "Trigger 1" }
          - { number: 4, name: "Trigger 2" }

Location

Use the board's /dev/serial/by-id/ path, which mimick peripheral list shows for every USB serial device the bench detects. CH340 boards report the USB ID 1a86:7523, so their path usually starts with usb-1a86_.

Relay

The relay interface takes a channels list with at least one entry. Each entry maps a relay on the board to the name you address it by:

Key	Required	Allowed values
number	Yes	1 to 4, each used once
name	Yes	Any label

A relay you leave out of the list isn't available.

After every write, the bench reads the board's status back and checks that the relay changed state. A stuck relay returns an error instead of reporting success.

Use it

mimick relay list -p button_relay
mimick relay write -p button_relay 1 on
mimick relay write -p button_relay 1,2 off,off

Channels are numbers or names. In the web UI, select Open relay controls on the peripheral's row in the bench's Inventory tab.

mimick relay name renames a channel only until the peripheral reopens, for example after the bench restarts. To keep a name, set it in the file.