So far, we have used the BBB's GPIO, SPI, and I2C functionality for our interfacing. These are not the only interfacing options that the BBB offers, though. The following are a few other interfaces that you should keep in mind as you consider Android projects on the BBB.
Embedded within the BBB's AM335X processor are a pair of programmable real-time units (PRUs). These units are clocked at 200 MHz, so they execute programs at the rate of a single instruction every 5 ns. The kernel loads programs into a PRU and then instructs the PRU to begin execution. Communication between the PRU and the kernel occurs via shared memory. The execution of PRUs is completely separate from that of the main processor, so pushing the PRUs to their limit will not have a performance impact on the main processor unless some coordination between the processor and a PRU is required.
There are a number of GPIO pins that can be muxed so that they fall under...