More microcontroller devices are using 'smart LCD' displays to output visual information. The following discussion covers the connection of a Hitachi LCD display to a PIC microcontroller. LCD displays designed around Hitachi's LCD HD44780 module, are inexpensive, easy to use, and it is even possible to produce a readout using the 8 x 80 pixels of the display. Hitachi LCD displays have a standard ASCII set of characters plus Japanese, Greek and mathematical symbols.
The Serial Peripheral Interface Bus or SPI bus is a synchronous serial data link standard which opererate in a full duplex mode. Devices communicate in master or slave mode where the master device initiates the data frame. Multiple slave devices are allowed with individual slave select lines with the chip select.
Introduction to I2C
An Inter-IC bus is often used to communicate across circuit-board distances. Here's a primer on the protocol.
At the low end of the spectrum of communication options for "inside the box" communication is I2C ("eye-squared-see"). The name I2C is shorthand for a standard Inter-IC (integrated circuit) bus.
I2C provides good support for communication with various slow, on-board peripheral devices that are accessed intermittently, while being extremely modest in its hardware resource needs. It is a simple, low-bandwidth, short-distance protocol. Most available I2C devices operate at speeds up to 400Kbps, with some venturing up into the low megahertz range. I2C is easy to use to link multiple devices together since it has a built-in addressing scheme.