I2C

I2C is a neat little bus that uses two lines - clock and data - to allow any number of masters and slaves to talk together at 100KHz or 400KHz or 1MHz. The rate isn't massive, but for non-bandwidth-critical applications like controlling LCDs and LEDs and accessing small memories and so on, it's pretty useful. The SMBUS (used on PC mainboards) is a I2C bus too.

The LPC21xx chips have a hardware I2C interface that can be left to its own devices to transfer a byte at a time either way, and if configured to act as a slave will interrupt the processor when addressed, which saves a lot of CPU time over "bit banging".

• http://www.ping.be/~ping0751/i2c.htm - has a list of I2C device manufacturers.
• http://www.interfacebus.com/Design_Connector_I2C.html - I2C bus information (has a link to the specification)
• http://www.epanorama.net/links/serialbus.html#i2c - More I2C information
• http://www.philipslogic.com/i2c/ - I2C page at Philips

Some I2C devices:

• MCP23016 - 16 I/O lines
• http://www.philipslogic.com/products/i2c/ - Philips I2C products
• STA013 - MP3 decoder