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SOFTWARE IMPLEMENTATION OF I²C PROTOCOL

by Dariusz Caban

Start ý The Bus ý The Protocol ý The Process ý Conclusions ý Sources and PDF

CONCLUSIONS

Compared to other competing synchronous serial interfaces, Microwire from National Semiconductor and SPI from Motorola, I²C has the least hardware requirements. Only two I/O pins of the microcontroller are needed to communicate with multiple slaves, because each slave is identified by its unique address, not by a separate select line. Also, because the I²C protocol is level-sensitive, its noise immunity is likely to be higher than in edge-sensitive competitors. And, unlike Microwire and SPI, I²C slaves provide feedback to the master, which indicates whether or not transmission was successful. Until recently, the I²C protocol was significantly slower, but in 1999 a high-speed mode was introduced, which offered rates up to 3.4 Mbps.

In this article, I have presented an example all-software implementation of the Standard mode of the I²C protocol. The source code was written in a high-level language, and you can easily see that it is not complicated. Although the compiler used was rather old [2], small-size executable code was produced.

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