Human Machine Interface (HMI) Solutions

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 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 several design challenges which include rapidly changing HMI requirements, smaller form factors, and improved battery life. Actel's line of ultra-low-power, reprogrammable flash FPGAs provides solutions to address these challenges.

Using Actel's HMI solutions provides a host of key benefits:

• Actel's ultra-low-power flash FPGAs can be used to implement customized HMI controllers
• Actel's HMI solutions demonstrate integration of several control functions in a single, feature-rich, low-cost, and small form factor FPGA
• Reprogrammability allows for rapid development and fast time-to-market
• Ultra-low-power IGLOO FPGAs with Flash*Freeze technology help reduce the power consumption of the overall system, resulting in increased battery life
• Design examples can be downloaded from the Actel website
• A network of solution partners meets your design needs

The block diagram above shows a design that implements multiple control functions on a single Actel flash FPGA device. This implementation can control the keypad, brightness of white LEDs, color mixing for red-green-blue (RGB) LEDs, and tone generation at the same time. The keyboard control interfaces with a 6x3 keypad (18 keys). This control also contains debounce logic for the keys. The design interfaces with the LEDs and speaker via pulse-width modulation (PWM) logic. An 8-bit PWM is used to control brightness and dimming functions.When interfacing with the color (RGB) LEDs, three PWMs are time-division multiplexed to drive multiple LEDs simultaneously as well as reduce power consumption. The tone generator logic interfaces with a speaker on the board via a 16-bit PWM. For more details on each of the HMI device controller and to download the design examples for each, please visit the HMI Daughter Card for Actel's Icicle Kit web page.

Keypad Control This design senses the keypad (a standard cell phone keypad with 18 keys) by scanning the 6 rows and reading the 3 columns. This design can be targeted to any application requiring a keyboard interface in a matrix form. The row-column matrix combination can be easily changed to cater to the designer’s requirements. The scan method can also be integrated into an interrupt-based control logic function when interfacing to a processor.
Brightness Control for White LEDs This design 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 This design controls the color mixing for the red-green-blue (RGB) LEDs using three PWM signals. This scheme can be used to generate a keypad backlight or LCD backlight of any color, or illuminate a particular area with required color using the RGB LEDs. The brightness and color of the RGB LEDs are controlled through three 8-bit PWMs. These PWMs signals are time-division multiplexed to reduce power consumption.
Tone Generation This design generates 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.

Actel offers a demonstration platform that showcases an IGLOO low-power FPGA as a controllers for various HMI functions. The platform consists of an HMI Daughter Card for Actel's Icicle Kit. The HMI daughter card has a standard cell phone keypad with switches, white and RGB LEDs, and a small speaker.

For a FREE demo, please contact your local Actel Sales representative.