Mountaineer Design Considerations
A device built out of a Gadgeteer mainboard and a number of attached Gadgeteer modules could conceivably be of all kinds of shapes, from a simple box to an arbitrarily complicated angled or rounded enclosure. A "pure" Gadgeteer mainboard only contains the standard 10-pin Gadgeteer sockets, while all "normal" connectors (for USB, Ethernet, radio antennas, and what have you) are put onto separate modules connected to the mainboard via ribbon cables. Exactly one of the modules is a "red" module, meaning that it provides the power to the mainboard and to all attached modules. All other boards are "black" boards, i.e., power consumers.
With the Mountaineer boards, we opted for a different engineering tradeoff and put the most important connectors - USB connector, plus Ethernet connector on the Ethernet mainboard - already on the mainboards. Power is provided through the USB connector, thereby resulting in "red mainboards". This approach saves space and cost, by combining one ore more add-on modules with a mainboard. As the mainboards are very small, this doesn't even much reduce the flexibility for placing the boards within an enclosure.
Mountaineer compass rose
By default, Mountaineer boards have their external connectors for USB, Ethernet, serial ports, power supplies, and radio antennas on the "north" side, connectors for deployment and debugging purposes on the "south" side. Modules that provide connectivity to the Internet are placed to the "west", while modules that implement sensors or actuators - the "field" modules - are placed to the "east". We also call the east the "field side", and the west the "cloud side" (see the figure below).
In a complete device there is typically at most one cloud module at the west side of the mainboard, but there may be more than one field module at the east side.
As a consequence of this architecture, analog inputs (socket type "A"), analog outputs (socket type "O" and "P" for PWM) are placed on the east sockets of the mainboard. Also, there are communication sockets of type "U" (UART) and "I" (I2C) on the east side. The west side is more communications-oriented, with a UART without hardware handshaking ("U") and a UART with hardware handshaking ("K").
External connectors of field modules can vary considerably depending on the application requirements. Where possible, they are located at the "east" side.
Some modules may be useable both on the field side and the cloud side. For example, a Bluetooth module may enable Internet access indirectly through an Android smartphone (cloud side), or may enable access to Bluetooth sensors (field side).
High speed lane
In the middle row of sockets, the "high speed lane", there is an SPI bus ("S") on the west side, and another one on the east side. These buses allow to realize independent high-speed data transfer both with the cloud side and the field side.
All boards have the standard height of 57 millimeter. In accordance with the Gadgeteer design rules, every Mountaineer board has a width of (n * 5) + 7 mm. In general, boards are made as narrow as possible, to minimize the space that they occupy.
Our mainboards and modules all have the vertically oriented sockets placed on the following y-coordinates, measured from the lower edge of the board:
Upper socket: 42.2 mm
Middle socket: 28.5 mm (1/2 of our standard height of 57 mm)
Lower socket: 14.8 mm
These coordinates denote the center of a socket.
The sockets have a distance of 4 mm from the left/right side of the board, in order to keep a minimum of 0.5 mm between copper pad and board edge.
Note that in the above illustration, the sockets are oriented correctly for mainboards. For modules, they would have to face the other way, i.e., would have to be rotated by 180 degrees.