The information below is taken from MDK v.0.2
All modules require at least one interface block to exchange power, data, and detect/wake signal between modules and the Endo. Some modules may also send RF signals through the interface block to another module on the device.
The interface block hosts electrical, data, and RF connections between modules and the Endo. The Ara platform utilizes a contactless inductive interface for high-speed data transfer between modules and the Endo. The Network Stack section details the contactless data transfer mechanism.
Each interface block is composed of 4 electrical connections (2 for power, 1 detect/wake, and 1 RF) and 8 data interfaces transferred by means of 4 contactless inductive pads as shown in figure below (1×2 modules have 2 sets of electrical connections to enable module insertion in both orientations). Details of the contactless inductive interface is provided in the Network section. Additional details of the objective interface block design will also be provided in a future MDK release.
The interface block is itself mounted and printed on a separate PCB (printed cirquit board). The interface block PCB is then soldered to the main PCB. When installed into the module, the interface block PCB should be completely flush with the corresponding opening in the module base. The interface block PCB must follow the geometry specified in the module template CAD and EDA files provided in the reference implementation withing MDK (Module Developers Kit).
The interface block in the current prototype platform differs from the objective specification. Instead of contactless data transfer with inductive pads, the prototype uses electrical signaling between the gold-plated copper pads on the module interface block and spring pins on the Endo for data transfer (i.e., the same method used for power transfer). The shape of the prototype interface block pad is round to match the spring pins on the Endo. The module template section provides design artifacts for the prototype interface block reference
The prototype interface block provides 8 data pads: two bidirectional M-PHY data lanes with 8 differential pairs (2 TX pairs and 2 RX pairs), a power pad, a ground pad, a detect/wake pad, and an RF pad. Figure and table below detail the pinouts of the prototype interface block.