StackableUSB Description

StackableUSB uses the original USB 2.0 specification, but defines the interface as a Board-to-Board stackable interconnect. Using the same idea as PC104, without the legacy interfaces. Read more on the PC-104 Interface Description, offered to show an example of a standard that stacks boards one on top of each other. StackableUSB requires one Single Board Computer [SBC] acting as the Host and up to ten USB peripheral boards. Up to five peripheral boards may be stacked above the SBC and a maximum of five stacked below the SBC. The card stacks could be used by them selves, in a stand-alone fashion or mounted on some other embedded main-board [mother-board]. The maximum number of boards may have changed, seems as if that number was reduced to eight total cards.

StackableUSB takes on the same board size as the PC-104 specification, so they could be attached to PC-104 stacks or EPIC Main Boards. The EPIC standard is a Single Board Computer [SBC] that is used as a carrier card for PC-104 [and now StackableUSB] board stacks. The StackableUSB also specifies USB connectors so they consume much less board space than the original PC-104 or PC-104+ standards. Reducing the amount of space required by the interface connectors means more board area for components and functionality.

The board form-factor is defined as [PC-104] 3.775 inches x 3.550, but the spacing between board has changed. The StackableUSB specification defines 0.591 inches between boards [15mm], while the PC-104 standard allowed 0.60 inches between cards. Of course the style of connector is completely different as is the locations. However the mounting holes are kept in the same location as the other spec so this new standard could be used on EPIB boards as stated above.

StackableUSB is basically a different implementation of the USB standard. So the specification references the electrical standard covered in the main USB standard, but does not include it. The StackableUSB specification covers the architecture, board format, connector size and location, and the pin-out between boards. So StackableUSB is more like a mechanical standard, which uses the USB standard to cover the electrical specs and protocol.

Main Section USB Interface Description.

Universal Serial Bus Specification, Revision 2.0, April 2000
StackableUSB Specification, Revision xx, 2006
Refer to

StackableUSB Connector Manufacturers

Samtec {Dual 26-Pin Rows, Male/Female, Surface mount
15.24mm stack height for top and bottom board stacking}

StackableUSB Related Products

Samtec {15.24mm standoff}

Editor note; this is not the same as two USB connectors stacked on top of each other, other wise known as a double-stacked connector. The double-stacked connector is just two individual USB connectors ganged together and have nothing to do with a stackable-USB interface.

Basic PC-104 Board Size
PC-104 Stack

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Modified 2/14/12
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