For those who own a Texas Instruments Compact Computer 40 (CC-40) or a CC-40 peripheral which uses the TI HexBus 4 bit communications protocol but want to use the device with a TI-74 BasiCalc unit or peripherals, which use an electrically compatible but physically distinct configuration called DockBus, this adapter converts between the two. Since it is passive, it can be used in either direction, and the PCB can be assembled to plug directly into either a HexBus or DockBus connector on a device and then use a cable to connect the other device. These include pin connectors on both sides preinstalled.

The design is open source and available on GitHub: https://github.com/go4retro/HexBusAdapter