Embedded Open Modular Architecture/EOMA68/Passthrough
These cards allow access to the features of Motherboard Chassis devices performing little or no conversion of signals and passing them through to the EOMA-PCMCIA connector. Examples include:
- A tablet with a passthrough card could be used as a portable LCD monitor, including its touchscreen converted for use as a USB device.
- A large LCD Screen with a passthrough card could be used as a LCD monitor, with the ability to upgrade it simply by swapping the passthrough card for a TV card or CPU card: the LCD Screen becomes a fully-functioning computer or a TV.
- A keyboard with a passthrough card is a plain keyboard, perhaps with extra USB ports. Removal of the passthrough card and insertion of a CPU card turns the keyboard into a fully-functioning computer.
- A laptop with a passthrough card is a strange concept! It offers the use of the keyboard and mouse as USB devices, allowing it to be plugged into a Desktop PC, and also allows the LCD screen to be used for display purposes - again on a Desktop PC or other suitable device.
These two examples are incredibly simple. Connectors for Ethernet, USB and eSATA are simply passed straight through - literally - to the PCMCIA connector. HDMI input is converted into 24-pin RGB/TTL: a suitable IC is the Texas Instruments TFP401a. More advanced versions would convert HDMI Audio into, for example, USB Audio. Even more advanced versions would have the means to change the brightness, contrast and gamma correction of the picture being displayed, perhaps have two HDMI inputs and allow picture-in-picture and selection between the two inputs.