BBB interface expansion

High speed data acquisition cannot be made possible without a customized hardware system connected to a cpu like AM335X.  In my previous article, I mentioned about GPMC interface that can be used to interface with FPGA, the customized hardware system can then be implemented by FPGA for high speed data acquisition. 

GPMC function can be multiplexed from P8/ P9 expansion headers on BBB, However some of those GPMC pins are already used by eMMC, therefore, a small modification of BBB is required.

I removed the pull-high resistors of the eMMC pins so that the pins can be multiplexed to GPMC. Linux will have to be boot from SD card since eMMc function is altered by GPMC. Get familiar to remove 0402 sized resistor.