CHAPTER 6
Interfacing to the Beagle Board Input/Outputs

This chapter integrates the Linux, programming, and electronics groundwork from earlier chapters to show you how to build circuits and write programs that interface to Beagle board single-wire inputs and outputs. In this chapter, you will see practical examples that explain how to use a general-purpose input/output (GPIO) to output a binary signal to switch on an LED or to read in a binary input from a push button. Optocoupler circuits are discussed so that you can safely interface to externally powered circuits. Also included are the steps required to read in an analog input and to send out a pulse-width modulated (PWM) output. GPIO interfacing is first performed using sysfs to ensure that you have skills that are transferrable to other embedded Linux devices. Next, BoneScript and memory-mapped approaches are investigated, which are largely specific to the AM335x SoC. Finally, there is a brief discussion on the impact of udev rules...