On Tue, 23 Jun 1998, Mike Keitz wrote:

> On Tue, 23 Jun 1998 09:20:36 +0200 Charlos Potma <Charlos.Potma@RIVM.NL>
> writes:
> > I am now considering using a
> >PC mouse, or at least some part of it as an encoder.
> >The standard PC mouse seems to have a DATA and CLOCK
> >output. Does anyone here have detailed information on the
> >protocol used?
>
> Sounds like a PS/2 type mouse.  These use two TTL lines with
> bidirectional synchronous signals very similar to a keyboard.  A serial
> mouse would be simpler to use a since it sends data one way over one
> wire.  The data is just standard asynchronous at 1200 baud.  Microchip
> made some pre-programmed PICs once to use as mouse controllers.  The data
> for these had fairly good descriptions of the signal format.

I thought that I'd seen simple (no IC's or active components, just wires)
adapters to go between a serial mouse and a PS/2 bus mouse port. If what
you are saying is true, how can a simple adaptor convert an asynchronous
signal to a bi-directional synchronus signal? I could be wrong, its just
that I seem to remember these adaptors.

THanks,

Sean


>
> For a Microsoft-type serial mouse, groups of three 7-bit characters are
> sent LSB first with start and stop bits just like standard async data.
> The data is sent only after the user activates something on the mouse, if
> it is sitting still no data is sent.  The characters are:
>
> 1(LB)(RB)(V7)(V6)(H7)(H6) - (LB, RB are 1 if the button is pressed)
> 0(H5)(H4)(H3)(H2)(H1)(H0)
> 0(V5)(V4)(V3)(V2)(V1)(V0)
>
> The PIC would look at the MSB of each character and wait until one with a
> 1 is found, indicating the start of a new packet.  Then it could
> accumulate the V and H bits in proper order.  I think the two 8-bit
> numbers are two's complement reperesentation of how far the mouse has
> moved since the last report.
>
>
>
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