As embedded microcontroller-based products become more
sophisticated, additional emphasis is being placed on the design and
implementation of their user interfaces. Visually based interfaces are
commonly implemented with LCDs, LEDs, fluorescent displays, and
lights. Many of these components can be controlled directly by an
application’s processor without using additional components. Voicebased
user interfaces, on the other hand, are often implemented with
speech synthesizers, speech processors, sound generators, and digital
signal processors which operate in conjunction with an application’s
main processor. In addition to a processor dedicated to the generation
of speech, designs frequently require a memory device to hold the data
used by the processor, a loudspeaker, and audio amplification circuitry.
The added cost for components and space has limited the
implementation of speech-based user interfaces to higher end products
and products for the visually impaired. This application note discusses
adding a voice-based user interface to an application based on the
Motorola MC68HC(7)05J1A microcontroller. In particular, interfacing
members of the M68HC05 MCU Family to the Information Storage
Devices (ISD) 1000 and 2500 family of voice record/playback devices is
highlighted. The development of an audible thermometer application
concludes the discussion.