Monthly Archives: August 2013

PS/2 Keyboard Decoder

We have been working on a comprehensive PS/2 keyboard controller.  PS/2 keyboards are available in many shapes, sizes and specialty versions and most are low cost as well.  A problem with these keyboards are that they require fairly complicated code to read the data from the keyboard and translate it into a simple ASCII character.

There are a few PS/2 controllers on the market so why build another one?  The short answer is that none of the ones on the market meet our needs.  Most (All?) PS/2 controllers produce 5V signals and this is a problem for modern CPU’s that run on 3.3V.  The output ports available on the existing controllers are typically serial ports and some offer I2C interfaces.  We will offer serial, I2C and SPI outputs, simultaneously.  The power supply to the microcontroller is switchable between 3.3V and 5V to allow the keyboard decoder to be used with 3.3V and 5V systems without level shifters.  We also offer IO pins that signal when there is a character available, when the internal buffer is full and the state of the Caps Lock of the keyboard.

The first prototype had a few issues such as the PS/2 connector had to be soldered onto the bottom of the board, the reset signal was broken and some other minor issues.  The second prototype is in much better shape and we are coding away furiously.  Once the board and the code is fully tested it will be for sale at a reasonable price.  The schematic will be available to everyone  and the source code will be available to all who purchase the controller.  You will be able to modify the code to suit your own personal requirements.  The decoder is programmable without any hardware and with free software.  The CPU is quite capable and fast and has several IO pins available so you may be able to fit your entire project onto the controller.