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Raspberry Pi For Dummies by Mike Cook, Sean McManus

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Investigating Converter Chips

Special chips have all the circuitry and can do all of these processes for you. Your computer can connect to these chips in a wide variety of ways. One of the simplest ways is called a parallel connection, where each signal in the circuit has a separate GPIO pin allocated to it. It is the fastest way, but it uses a lot of GPIO pins. A more efficient way is to send data one bit at a time over a single wire along with another wire that changes to signify a change in data. This other wire is called a clock signal. One of the more popular implementations of this sort of communications is to a protocol called I2C.

This protocol has been around for a long time. It was first produced in 1982 by Philips to allow its ICs to communicate. The initials stand for Inter-Integrated Circuit communication. This is sometimes abbreviated to IIC or I2C, otherwise known as twin wire. It’s pronounced “eye squared cee” and should be written as I2C, but not all computer systems or languages have the facility for superscript capability, so it remains I2C in most places.

The idea is that communication takes place over two wires: One carries the data and the other the clock. As there is only one line for the data, and that can only be high or low, transmitting numbers or bytes (a collection of 8 logic levels defining a number) happens serially; that is, one bit at a time. The rising edge of the clock line tells the receiver when to sample the data signal, and each message to ...

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