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Issue #201 April 2007
ATir Keyboard Interface
by Steven Savage
Start | System Overview | Keyboard | IR Remote Operation | ATir Hardware | Operation | Nice Solution | Sources & PDF
System Overview
Small on pins
does not necessarily mean small on performance. Take the Atmel ATtiny
series. These tiny microcontrollers can do a lot more than act as a programmable
555 timer or implement some simple logic function. In this project, the
microcontroller is used to decode and encode PS2 keyboard signals and
perform data compression and storage in real time. It can also be used
to decode signals from an IR remote, with a few external components to
get the job done. If you’re more of a software person and less of a hardware
designer, this may be the project for you. I admit that Figure 1 is rather
simple, but isn’t there a certain elegance in simplicity? Another advantage
of this simple design is its ease to implement on a budget.
The human interface to most PCs consists of a keyboard and a mouse. While this is convenient for many tasks conducted with a PC, some applications warrant remote operation. For example, when conducting a Microsoft Power Point slide presentation, it is nice to be able to advance the slides without having to operate the keyboard. For PCs dedicated to running multimedia applications in a home theater environment, it is easier to press the Play button on a remote control than to operate a keyboard. Some industrial systems use PCs running a custom software application that may only require a small set of keyboard commands to operate, while most of the time the keyboard remains unutilized, collecting dust. Those are just some of the applications that could benefit from the use of the ATir keyboard interface.
Using a keyboard, the ATir is programmed to respond to a key press on a remote control and output a block of keyboard data. For example, the ATir could be programmed to work with Power Point by entering Program mode, selecting a button on the remote control (say your remote has a “Play” button), pressing the F5 key, and saving the keyboard macro by pressing the same button on the remote. Now, with Power Point started, when you press the Play button on the remote, ATir sends the codes for the press and release of the F5 key and the Power Point presentation starts. To go to the first slide in the presentation, the keyboard shortcut 1 + Enter can be used. This keyboard macro could also be linked with another remote control push button.
Key sequences of up to 64 keys can be stored in an individual
macro. These macros are stored in the EEPROM section of the microcontroller,
so the data is retained after power is removed. After macros are defined,
the ATir can be connected to a PC without a keyboard and it will perform
the necessary handshaking during boot up to enable operation. A keyboard
can also be connected to the ATir after the system boots and the ATir
will relay information between the keyboard and PC.
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