PS/2 -> Indigo adapters
dholland at woh.rr.com
Tue Mar 8 12:55:40 CST 2005
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:
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.
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