On Wed, 2 Nov 2005, Andre Abelian wrote:

> Hi to all,
>
> Based on what I understood PS2 keyboard uses bi-directional
> communication. I am not sure about the mouse
> does it work similar way "bi-directional" or mouse is just output device?
> my main question is Can I use PIC's hardware SPI interface for keyboard or
> mouse. I like PIC18F parts. any info will appreciate.

The PS2 if is NOT SPI, it is PS2. You can find a fairly complete 
description in the datasheets of PS2 devices (f.ex. mouse controllers 
from Holtek and others, including HP/Agilent). Please find them and read 
them carefully. It is not very easy to make PS2 work but it can be done 
and it has been done many times. There is pic code for interfacing with 
PS2, look on the web. The device recognition is done by the host and an 
id string is sent by the device to the host. This tells it what it is. 
The host then uses the device as intended (mouse, keyboard etc).

Peter
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