The AIOC is a versatile, open-source digital interface for amateur radio. Despite its name, the AIOC is not a cable, but instead is a compact PCB that serves as a bridge between computers and a wide range of HTs. It combines the functions of multiple other cables, acting as a sound card, serial port, and PTT.

The AIOC's core design philosophy is focused on affordability and hackability. By leveraging low-cost, high-volume PCB fabrication services like JLCPCB and minimizing the Bill of Materials (BOM), the AIOC project makes participation in digital modes significantly more accessible to the broader amateur radio community.

Historically, interfaces for digital modes such as APRS, packet radio, or Winlink involved either expensive, dedicated Terminal Node Controllers (TNCs) or bulky sound card interfaces. The AIOC, by being inexpensive to produce and compatible with the ubiquitous and affordable Baofeng and similar HTs, effectively lowers the financial barrier to entry, allowing newly licensed hams and those on a budget to experiment with and operate on these powerful networks.

The AIOC has 3 key functions:

1. USB Sound Card: The AIOC appears as a standard USB audio interface, providing mono mic input and a mono speaker output. This enables the software-defined digital interfaces to send/receive audio.
2. Virtual TTY/COM port: The AIOC creates a virtual serial port, which presents as a COM port on Windows or a /dev/ttyACM device on Linux and MacOS. The serial port serves two purposes. First, it allows the AIOC to act as a programming cable for the radio, using software like CHIRP. Secondly, it provided a traditional method for Push-to-Talk (PTT) keying, where the software asserts the serial control lines (typically DTR or RTS) to trigger the radio's transmit.
3. HID Endpoint: Start with firmware version 1.2.0, the AIOC shows up as a Human Interface Device (HID) that provides general-purpose input/output (GPIO) for PTT. Starting with version 1.3.0, the AIOC can fully emulate a CM108, enabling compatibility with a wider variety of software, including AllStarLink.

The AIOC's use of a powerful and programmable STM32 has enabled the dynamic evolution of the AIOC, with minimal hardware changes over time.

We encourage users to hack, play with, and modify their AIOC. If you have a feature you'd like, you can add it yourself and open a PR, so we can work to add it to the main firmware. See the future work section for more.