Interfacing to the Beagle Board Input/Outputs
Derek Molloy · 2018
This chapter integrates the Linux, programming, and electronics groundwork from earlier chapters to show a user how to build circuits and write programs that interface to Beagle board single-wire inputs and outputs. This chapter presents 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. 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 the reader has 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 and Linux permissions on GPIO interfacing.