PS/2 -> Indigo adapters

[David Holland]

On Tue, 2005-03-08 at 15:41 +0000, Jules Richardson wrote:
> On Tue, 2005-03-08 at 09:21 -0500, David Holland wrote:
> > Hi, 
> > 
> > Has anyone successfully built one of the PS/2 -> Indigo adapters off of
> > the following page? 
> 
> No, but I've seen that page before - lack of a PIC programmer has
> stopped me building one (or two). We've got a 4D/25 and two Indigos, but
> only one SGI keyboard between the three...

I built this thing: 

http://www.bobblick.com/techref/projects/picprog/picprog.html

Component cost is pretty low, and the propic2 software off that page
(while Windows based) programs the 16F628's well enough.  

(Verify doesn't work however. - Just read the device, and eyeball it.)

> 
> > When I hook my scope up to the clock and/or data PS/2 lines, I see no
> > data being received from the mouse.
> 
> Obvious one: have you checked that the mouse is getting power? 

Yup.   Mouse is getting power.   One of the first things I verified. 

> 
> I don't actually know whether the PIC is supposed to generate the mouse
> clock or whether the mouse does though... if the former then you'd
> presumably see something on the clock line if the PIC was running.

According to the data I found on the PS/2 spec, it depends.    If the
mouse is talking, it twiddles the clock line.  If the "host" is talking,
it twiddles the clock line.

I _think_ I see a little initialization data pass down the line, to the
mouse, when I first power up the device, but my o'scope isn't a memory
type, so it might just be power up noise. 

Hence my suspicion that it might be a initialization issue.

> 
> Looking at the schematic, how the heck do PICs reset at power-on?

Internal reset @ power-on circuitry.    

You also need to tie ~MCLR to VDD via a resistor. 
(Which is an error in the schematic. - And my PIC's wouldn't "run" till
I did so.)  

I used a couple of 4.7K, as it was what I had lying around. 


> Presumably it's internal - I'm suprised reset isn't under user control
> on one of the pins though...

If I understand the datasheet, its a function of ~MCLR, and the config
bits, and if you were to drop it to ground, it'd reset the device. 

> 
> cheers
> 
> Jules
> 
>