Human Machine Interfaces for Portables

FREE Design Examples, Design Tools, and Daughter Card

The market for portable applications is growing tremendously, specifically in consumer, medical, industrial, and military markets. In addition to display and storage functions, portable devices have one or more kinds of human machine interfaces (HMI) for the user to interact with the application. In newer portable devices, HMI interfaces such as alphanumeric or qwerty keypads, touch keypad/displays with white or color LED backlighting, programmable keys/switches, joysticks, scroll wheels, and buzzers/speakers are becoming more and more prevalent. Designers of portable applications face rapidly changing HMI requirements, demand for very small form factors, improvements in battery life, and other complex design challenges. Actel's line of ultra-low-power, reprogrammable flash FPGAs provides solutions to address these challenges.

The Icicle Demonstration Kit and HMI Daughter Card

Actel's IGLOO Icicle Kit, based on the 5 µW IGLOO device, is a low-cost, portable, low-power demonstration platform that can be powered by a built-in rechargeable lithium-ion battery, USB cable, or external power supply.

The HMI daughter card consists of a standard cell phone keypad with switches, white and RGB LEDs, and a small speaker.

HMI Controller Design

The figure above shows a block diagram of an IGLOO design that controls the keypad, brightness of white LEDs, color mixing for RGB LEDs, and tone generation. HMI control design examples aid in the development of HMI control applications and are available for free download from the Actel website, independent of the HMI Daughter Card.

• Keypad control senses the keypad (a standard cell phone keypad with 18 keys) by scanning the 6 rows and reading the 3 columns. This design targets any application requiring a keyboard interface in a matrix form.
• Brightness control for white LEDs controls the intensity/brightness of white LEDs by varying the duty cycle of the PWM logic. The 8-bit (256 steps) PWM drives the LEDs through a WLED driver chip.
• Color mixing for RGB LEDs controls the color mixing for the red-green-blue (RGB) LEDs using three PWM signals. This scheme can generate a keypad backlight or LCD backlight of any color, or can illuminate a particular area with required color using the RGB LEDs.
• Tone generation produces tones of desired frequency (period) and volume (duty cycle) using a 16-bit PWM signal. Tone duration and dampening can be controlled through additional counter logic.

To begin designing for portable applications with IGLOO FPGAs today, download and license the FREE Libero IDE software and HMI design examples. In order to try out the design on-board, you can order the Icicle Demonstration Kit from Actel and the HMI Daughter Card from Avnet Memec.