USB I2C Protocol And Converter Design

USB I2C Protocol And Converter Design

I2C Protocol

USB i2C converters facilitate data transfer between USB and i2C protocols. While they come in different designs, most are bilateral meaning either end can act as master and slave. Software is used to facilitate slave/master capability.

USB to I2C converters make it possible for different bus participants to be addressed. These include sensors, IO-expanders, 7 segment displays, real-time clocks, LCDs, and tone generators among others. Before we proceed, let us take a look at how i2C protocol works.

I2C protocol is a communication procedure that allows data transfer between devices using two bi-directional lines. The first line is the serial clock while the other is the serial data line. The master device generates Start and Stop conditions as well as the clock signals, while the slave sends an Acknowledgement signal upon receipt of each byte.

With a PC acting as the slave, an i2C master addresses the converter as slave then writes data onto the bus. It therefore becomes possible to send data to a PC using USB. Once data transfer is complete, an interrupt signal informs the i2C master that data is ready to read.

Hardware Features

An important feature for most USB i2C converters is a level shifter, circuitry that makes it possible to connect the device on buses of diverse voltages. Converters further have EEPROM memory on board, with some bytes reserved for internal use and the rest left for the user. Some designs feature Indicator LEDs that show when power is ON as well as a link from the converter to the host device.

Different manufacturers have their converters configured differently. Consequently, it is essential to refer to the user manual before plugging a converter to a COM port. While some converters feature a level shifter, others can only be operated at 5 volts. We also find a difference in software where with some models you have to install drivers while with others you don’t.

Pin Configuration

USB to i2C converters mostly have five pins on the output side. Two of the pins provide power to your low-power device; two are the i2C bus connections, while the last is an input pin. Always refer to manufacturer’s manual to understand the functionality of each pin.

Minimum System Requirements

USB to i2C converters are meant to be universal thus will work virtually on any PC. To be on the safe side, ensure your PC has at least 8 MB of RAM and runs either 32-bit or 64-bit operating system. It should also have at least 20MB of free hard disk space. For converters that come with drivers in a CD, a CD ROM drive will be required for installation. Finally, the system must have 1.1 or 2.0 compatible USB port.

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