I2C-MMI

I2C-MMI

An universal I2C driven user interface controller

The specifications of a user interface subsystem are usually quite stable from project to project, but as each new project is often built around a new micro-controller the developer has to re-write and debug a full set of low level routines to handle these peripherals. Moreover a large number of I/O pins are usually dedicated to these devices, needing a higher cost micro-controller.

I2C-MMI is a dedicated and very low cost pre-programmed chip that :

Handles directly all the elements of a classic user interface : LCD, matrix keyboard, buzzer, but also rotary encoder and an extra "remote control" UART port ;

Is fully re-usable from design to design, without requiring exotic and high cost peripherals like serial driven LCD panels ;

Communicates with the host micro-controller through a standardized non-dedicated and high speed I2C bus ;

Off-load as many functions as possible from the main micro-controller.

With I2C-MMI, the total cost of the system is not higher, and often lower, than the cost of a classic design : The extra cost of the I2C-MMI chip is easily counter-balanced by a much smaller requirement on the main micro-controller in terms of I/O pins count and memory requirements. And the development costs, time and risks are far reduced, improving the time-to-market. More over, the I2C-MMI chip can be physically fitted on a front panel PCB, communicating to the main PCB over a simple 4 wire I2C & power connection, thus reducing dramatically the interconnection costs.

Here under a summary of the I2C-MMI chip specifications :

Built using a preprogrammed low cost 87LPC764 micro-controller;
2.7V to 5V operation, low power ;
Connection to the host micro-controller through a standard I2C interface (up to 400kbps) using a simple ASII based protocol ;
Drive any parallel LCD display in 4 bit mode, on-chip binary to ASCII conversion with formatting ;
Handle a 4x3 phone-type matrix keyboard, on-chip de-bouncing ;
Drive a piezo buzzer ;
Handle a rotary encoder for easy data modification ;
Drive a supplementary 19200 bps UART port, providing at no development cost a remote control feature to any equipment ;
On-chip numeric editing routines ;
"Pseudo-logarithmic" rotary encoder conversion, in order to manage large scale numbers ;

The I2C-MMI embedded software was developed mainly in C language.

A demonstration board reference design provide an I2C-MMI chip and all supported peripheral designs on a single front panel PCB :