Exploring Raspberry Pi

Chapter 9Enhancing the Input/Output Interfaces on the RPi

This chapter describes how the input/output interface capabilities of the Raspberry Pi (RPi) can be enhanced and extended using low-cost modules, integrated circuits (ICs), and USB devices. The RPi is a competent interfacing and physical computing device, but analog interfacing functionality is absent, and other input/output capabilities may need to be expanded for your applications. This chapter begins by describing how you can utilize the RPi's buses to add analog-to-digital and digital-to-analog conversion capabilities to the RPi. The chapter then describes how you can expand the number of available pulse-width modulation (PWM) outputs and general-purpose inputs/outputs (GPIOs) on the RPi. The chapter finishes with a discussion on the use of USB-to-TTL devices, which can be used to expand the number of available serial UART devices. This chapter also provides you with further experience of interfacing to SPI and I²C bus devices.

Equipment Required for This Chapter:

• Raspberry Pi (ideally an RPi 2/3)
• Analog-to-digital converter ICs (e.g., the MCP3208)
• Digital-to-analog converter ICs (e.g., the MCP4725, MCP4921/2)
• PWM expander module (e.g., the Adafruit PCA9685)
• GPIO expander ICs (MCP23017, MCP23S17)
• USB UART device (e.g., CP2102 or CH340G compatible)

Further details on this equipment and chapter are available at www.exploringrpi.com/chapter9/.

Introduction

The onboard input/output capabilities of the RPi are described ...