The description relates to prototyping systems, including hubs for electrically connecting devices. One example can include an electrically insulative substrate and at least two connector tabs defined by the substrate, each connector tab including a data contact, a power contact, and a ground contact positioned over the substrate. A data bus can be positioned relative to the substrate and electrically connect all of the data contacts, a power bus can be positioned relative to the substrate and electrically connect all of the power contacts, and a ground bus can be positioned relative to the substrate and electrically connect all of the ground contacts.