k804IO

A small Python library for driving the digital I/O (and LED) outputs of OnLogic Karbon/K804-series computers over their onboard MCU serial console.

It wraps the dio set <group> <channel> <true|false> shell command exposed by the OnLogic firmware, so instead of opening a serial port and writing raw commands by hand you get a small Python object model: find the device, open the port, declare the channels you want to drive, and turn them on/off.

How it works

OnLogic Karbon/K804 units expose an MCU shell over a USB-serial interface. That shell accepts commands such as:

dio set LED0 0 true    # turn on LED channel 0 of group LED0
dio set DIO0 2 false    # turn off digital output channel 2 of group DIO0

See OnLogic's firmware shell documentation for the full command reference: https://static.onlogic.com/resources/firmware/documentation/shell.html

k804IO automates:

1. Finding the device — polling /dev/serial/by-id for an entry matching usb-OnLogic_*if00.
2. Opening and quieting the serial console — disabling the shell_uart and onlogic_vcom_can logs and shell echo so the port only carries the commands you send.
3. Modeling digital channels as Python objects you can turn on, turn off, or pulse for a duration, with optional inverted logic.

Requirements

• Python >= 3.8
• pyserial
• Linux, with the device enumerated under /dev/serial/by-id/ (relies on udev's by-id symlinks)
• Permission to access the serial device (typically membership in the dialout group, or running as root)

Installation

From the project root:

pip install .

or, for local development:

pip install -e .

Usage

Karbon804Terminal is a context manager: on __enter__ it searches for the OnLogic serial device, opens the port, silences shell logging/echo, and hands you a K804DigitalIOController at terminal.digitalIOController. On __exit__ it closes the port.

from time import sleep

from k804IO.k804 import Karbon804Terminal

with Karbon804Terminal() as terminal:
  # Declare the channels you intend to drive before using them.
  terminal.digitalIOController.createDigitalChannel("LED0", 0)
  terminal.digitalIOController.createDigitalChannel(
      "DIO0", 0, invertLogic=True
  )

  # Turn a channel on / off.
  terminal.digitalIOController.setDigitalOutput("LED0", 0, True)
  sleep(0.5)
  terminal.digitalIOController.setDigitalOutput("LED0", 0, False)

  # Pulse a channel on, then off, after a delay.
  terminal.digitalIOController.setOnAndOff("LED0", 0, 0.05)

See src/k804IO/example.py for a longer example that cycles through the four LED0 channels and declares an inverted-logic DIO0 group.

Digital groups and channels

• A digital group (e.g. "LED0", "DIO0") is a named array of outputs on the MCU firmware side; a channel is that array's index (e.g. 0-3).
• invertLogic=True flips the electrical sense of a channel — calling turnOn() sends the firmware a false command and vice versa. Use it for outputs wired active-low.
• Channels must be created with createDigitalChannel before they can be addressed by setDigitalOutput / setOnAndOff — the controller keeps them in a {group: {channel: OnlogicDigitalOutput}} dict and will raise a KeyError for an undeclared group/channel.

Device discovery and timeouts

Karbon804Terminal.findOnlogicSerialPort() polls /dev/serial/by-id once a second for up to 60 seconds looking for an entry named usb-OnLogic_*if00. If no matching device shows up in that window, or the port can't be opened, the terminal prints the error and exits the process (sys.exit(1)) rather than raising.

Project layout

src/k804IO/
├── k804.py                    # Karbon804Terminal: device discovery + serial session context manager
├── k804_digital_controller.py # K804DigitalIOController: channel registry / high-level API
├── onlogic_driver.py          # OnlogicDigitalOutput: builds and sends the raw `dio set` commands
└── example.py                 # Runnable example cycling the LED0 and DIO0 groups

License

MIT — see LICENSE.