Pinmuxing on the BeagleBone

Pinmuxing is a combined software and hardware concept that embedded users, such as the BeagleBone users, must be very aware of if they are using anything other than the basic functions of the BeagleBone. Any interfacing using the expansion connector P8 and P9 is likely to involve the pinmux unless the hardware being interfaced matches the default settings. Some of the off-the-shelf expansion boards come with configuration settings to automate this process. Regardless of whether it is automated, it is a good idea to at least confirm the pinmux settings. As described in Chapter 7, Interfacing with the BeagleBone, pinmux is used to select one of the eight functions on each signal from the SoC. It is the last part of the SoC before a signal leaves and the first part before a signal enters the SoC.

From a software standpoint, it is possible for the kernel driver to be configured perfectly and yet any external connected hardware to the SoC would not work. The pinmux...