[Coco] [Bulk] AT306 Mouse Question

[Gene Heskett]

On Saturday 08 September 2007, Joel Ewy wrote:
>Paul Fitch wrote:
>> There is a 3-pin header on the AT306 motherboard that says MOUSE.  How do
>> I use that?
>
>My assumption, from the era in which the AT306 was produced, would be
>that that is a serial port.  So you should have a ground wire, a
>Transmit Data pin, and uh, er...  That's not enough pins.  I don't know
>enough about the serial mouse protocol.  Does the mouse ever need to
>receive data from the host?  E.g., some kind of configuration packet?

The serial mice that were popular back about that time were transmit only, at 
1200 baud, 8n1, and either a 3 byte or 5 byte packet depending on how many 
buttons it had.  I used one such for quite some time on my coco.  It sent an 
x/y position move, and a switch status for any motion activity at all, or was 
quiet when just laying there.  The one I had did use the +-12 volts for a 
true rs232 interface, but I believe there was also some of the 'ps2' stuff 
that ran on straight 5 volts using a ttl version of the protocol, possibly at 
a higher baud rate, but I've no experience there.  I'd open it up and 
ascertain the supply connections, power it with 5 volts, and monitor the 
third line with a scope, which could tell you everything else you'd need to 
know.

>If not, then I suppose all you would need is power and data from the
>mouse to the host.  Power is probably supplied by a ground wire and one
>of the RS-232 handshaking lines (it would have to be one that's present
>in the 9-pin AT serial port).  Maybe CTS?  But on something like this,
>it's entirely possible that it's just connected to a +5 or +12 volt
>supply line.
>
>You can pretty quickly determine if this is anywhere close to correct if
>you have an ohm meter (nice if it has a continuity beeper).  See if one
>of the pins hooks up to ground, (either an obvious ground plane or a
>ground wire on the power supply connector), and then try to trace one of
>the other two to the +5 or +12V supply.  Failing that, turn the beast on
>and see if you get 5-12 volts on one of the pins with a volt meter.
>
>Probably somebody on this list has better information about the '306
>mouse port than I.
>
>JCE
>
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