To build an aide such as we wanted for Michael we needed to focus on the ultimate goal and the abilities of the individual. The ultimate goal was to provide as normal a method of communication as possible for the client. Ideally, that would be a device that would communicate the clients thoughts at speeds upwards of 180 words per minute, the estimated speed at which people are capable of speaking [TC84][GV83]. It was also important that the communication medium be clear human or human-like speech. Further, it would be extremely useful for the individual to be able to communicate any idea, including those not preprogrammed into the machine, to ensure a large-vocabulary[AS91][CV89]. Other considerations are durability, portability, and feedback to the user, information given to us by Kathy Bodine, augmentative specialist Easter Seals of Colorado. Specific client information from Michaels physical therapist, speech therapist, family, and experiences with other aides:
With this data, and remember a limiting factor of cost we were ready to go to the next step, the creation of the system outline.
From these goals and ability specifications a system outline/parts list was created. The primary output would be a digitized human voice (with as large a vocabulary as was feasible), for "Practical implementation of speech technologies depends on digital signal processing"[JF90]. It was not possible to digitize all of the words a client might want to use before hand and there were also storage space considerations when determining the vocabulary. To supplement the incomplete digitized vocabulary a clearly intelligible synthesized voice, with text-to-speech (the ability to "read aloud" the text that has been put into the system), was made available. For the eight buttons the client would use we selected arcade buttons. These are the buttons used in arcade games and vending machines and they are both durable and reliable. For the ON/OFF switch a large heavy duty-toggle switch was selected, as it uses a different type of movement than the buttons and could be easily manipulated by the client. An inexpensive, 7/11 bit, LCD was selected for client feedback. It has a wide viewing angle (60° ) and can be positioned so that the center of the viewing angle is aimed at the clients normal viewing position. For portability, it was decided to make the system so it would fit onto the clients wheel chair lap tray and run off batteries.
With this in mind we needed a computer to bring it all together. The necessary included:
Given this criteria we decided to use an Amiga 600 system because it fulfilled our requirements well. It has an 8 bit parallel interface for the LCD. It has fourteen buffered momentary switch detectors for the buttons to be hooked into (joystick ports). It has built-in sound and text-to-speech software is readily available. The system needs a fairly standard ± 12VDC, +5VDC, and GROUND voltages to run (see Power Supply Section). It has a footprint of 14"x10"x2" and costs just under $200. It is a multiprocessor computer and has very good capabilities for real-time applications (see Hardware Section).
The work of the project fell into two distinct categories, hardware and software. For clarity each of these will be covered in their own section. The hardware section will overview the components of the system and how they were interfaced, and the software section will overview the software construction and detail its use.
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