WHEN WE DISTIL computerised data processing down to its very essence, we require only two things of our computers—input and output, or I/O. You put data and commands in, and you receive processed data out. It’s a simple enough concept, but more than 70 years of electronic computers and the allied development of a veritable galaxy of peripheral devices make it more complicated.
This chapter attempts to demystify this complexity via an overview of I/O and the computer architecture behind it. Of course, there’s special emphasis on the Raspberry Pi, with an eye to some practical uses.
We begin with a short history of interfaces and their related protocols. Next, we examine various I/O schemes involving UARTs, USB, SCSI, IDE/PATA, SATA, I2S, I2C, SPI, GPIO and others. Yes, that is a double handful of acronyms, but most of them provide rather elegant solutions to specific I/O needs that we define and explain in this chapter.
The chapter concludes with a Raspberry Pi-specific section on using general purpose input output (GPIO). The two rows of GPIO pins on all the Raspberry Pi models differentiate them from most computers. Using these programmable inputs and outputs allow this credit-card-sized board (even smaller in the case of the Raspberry Pi Zero) to control everything from a tiny blinking LED light to massive electric motors drawing thousands of watts of power.
So, let us meet those cybernetic brothers: input and output.