What is it?

This is an adapter board that converts the Mini-B interface of a REV Expansion hub into a Type-C upstream and a USB A downstream connection.

Why did you make it?

Type-C all the things!

Type-C connectors are significantly more durable than Mini-B connectors. They're rated for more insertion cycles, are physically larger, and are reversible. They're nifty and belong on pretty much anything- like these boards. Adapting from the Mini-B connector on the REV Expansion hub to a Type-C port gives you a connection that is easily interchangeable and rotatable without worrying about mechanical rigidity.

This board also features a USB hub. When a team decides to use something like a webcam on their robot, it is common to end up with disconnection errors due to the amount of USB connection points. A robot could end up with up to five connection points between the control phone and the Expansion Hub- with this board, only two connection points are exposed. The USB hub chip (USB2422) is integrated onto the board to shrink the normal USB wiring setup on a robot.

The Mini-B connector is naturally strain relieved by the way it attaches to the Expansion Hub. 3D printed covers can also be modified to ensure that every single connection between the Hub and the phone are solid.

This board also features ESD protection on the data lines from the USB2422 IC.

Finally, this board is open source! The schematics, board files, BOM, and 3d-printable files are available on Github if you would like to make it yourself. Please note, however, due to the COTS nature of this product, any custom-built version may not be legal in certain robotics competitions.

Instructions:

Click "Datasheet" for assembly instructions!

3D printed cover?

If you do not have access to a 3D printer, you can opt to get the 3D printed case. This will be in a random color. If you already have a printer, the case files can be downloaded on Thingiverse.

Included in your package, regardless of selected option, will be a double-sided adhesive to secure the adapter to the REV Expansion Hub. The only hardware required are 3x M3 x 16mm long hex head screws, and 3x M3 nuts (preferably nylocs).

Adapter Cable?

Due to the nature of USB, it's not as simple as buying a Type-C to Micro-B cable online and calling it a day. The problem is that Type-C ports use CC pins for its "configuration", and Micro/Mini-B have a singular ID pin to signify host or peripheral modes; they're not natively compatible. All Type-C to Micro-B cables will be configured so the Type-C end is the host end, not the Micro-B end, which is what you need for this hub. The custom adapter cable has the ID pin of the Micro-B connector tied to GND to signify an OTG connection.

In short: if you have a phone/device with native Type-C, CC pull-down resistor pads are on the board, and you can use a standard Type-C to Type-C cable no problem.

If you have a native Micro-B phone, like all FTC legal phones:

• If you want a single cable, purchasing the adapter cable is necessary.
• If you are fine with using two cables, you can use a Micro-B to A adapter (OTG) connected to an A to Type-C cable.

Disclaimer: this device has not yet been explicitly ruled legal for use in FIRST Tech Challenge, FIRST Global or other robotics competitions, but is legal under specific game rules. Consult the rulebook for your specific robotics competition for clauses on COTS USB hub devices.