Digital I/O

The In-CarPC CQ40 series provides general-purpose digital I/O: two digital inputs (DI1, DI2), two digital outputs (DO1, DO2), and an ignition sense line (IGN), on an eight-way terminal block.

Digital I/O is a CQ40 series feature. On a CQ20, it is not available: pcu-cli dio reports ERROR: Digital I/O is not available on In-CarPC CQ20. and exits with code 2. See Supported Platforms for the feature comparison.

Older models: use CQUtils for now

pcu is new, and we are still backporting support for older In-CarPC models, including digital I/O. More models will be supported soon. If your machine is not yet supported, use the CQUtils program preinstalled on the desktop in the meantime. Not sure which applies to your machine? Contact In-CarPC support.

Connector pinout

The terminal block is wired in this physical order, left to right:

Position	Pin	Type	What it is
1	DI2	Digital input	Read-only sense input
2	DI1	Digital input	Read-only sense input
3	DO2	Digital output	Read/write output
4	DO1	Digital output	Read/write output
5	GND	Ground	Signal ground
6	IGN	Ignition sense	Read-only ignition input (the power symbol on the connector)
7	GND	Ground	Signal ground
8	12V	Power	Power pin

Wiring depends on your installation. This page describes only what each channel does in software.

Digital inputs (DI1, DI2)

The digital inputs read an external switch or sensor. The PC can read these lines but cannot drive them. High means voltage is present; Low means 0 V.

Example uses, illustrative only, since the wiring depends on the install:

• Reverse-gear signal, to switch to a reversing camera
• Handbrake or brake sense
• Door switch
• External push-button
• Accessory-on sense

For a worked example, wiring a door switch and reading it from your own software, see Detect a Vehicle Signal.

Digital outputs (DO1, DO2)

The digital outputs are lines the PC drives high or low. Use one to switch a low-current load such as a relay coil. Drive a relay rather than the load directly.

Outputs drive connected hardware

Setting an output high or low switches whatever is wired to it: a relay, a lamp, or another switch. Before you toggle an output, be sure you know what it controls.

Example uses, illustrative only:

• Reversing-camera relay
• Amplifier remote turn-on
• Work light
• Status indicator
• Auxiliary power relay

Outputs reset on reboot

Digital outputs are not saved. They reset to off on reboot or power loss. To have an output on after a restart, set it from a startup script, for example pcu-cli dio set do1 1 --yes. See Scripting and Automation for boot-time examples.

Ignition sense (IGN)

The ignition line reads whether the vehicle ignition or accessory feed is live. It is read-only and reads On when the feed is live. On the connector it is marked with the power symbol.

Reading and switching from the CLI

pcu-cli dio shows every channel at once:

$ pcu-cli dio
pcu v1.0.0  - In-CarPC CQ40 series Digital I/O
----------------------------------------
  DI1                 : Low
  DI2                 : Low
  DO1                 : Low
  DO2                 : Low
  Ignition (IGN)      : On

  Note: outputs reset to off on reboot or power loss; the state is not saved.

Read a single channel with pcu-cli dio get <channel>:

$ pcu-cli dio get di1
  DI1: Low

$ pcu-cli dio get ign
  Ignition (IGN): On

Set an output with pcu-cli dio set <output> <0|1>. It warns you, asks you to confirm, drives the line, and reads it back:

$ pcu-cli dio set do1 1
WARNING: digital outputs drive connected hardware (relays / switches / lamps).
Set DO1 = High? [y/N] y
  DO1: High - verified

The inputs (DI1, DI2) and the ignition line (IGN) are read-only and cannot be set. You can also work the channels from the Digital I/O page in the GUI, which draws the connector live and toggles the outputs with a confirmation. For the full command surface, exit codes, and scripting notes, see the Command Reference.

Permissions

Reading and driving the digital I/O needs low-level hardware access:

• Windows: run pcu as Administrator.
• Linux: run under sudo, or grant the port-I/O capability during setup. See Install on Linux.

Linux support for the CQ40 series has not yet been validated on hardware; see Supported Platforms.