Getting G3 Whisper Perch USB working

[croissantking]

Lots of corrections to this one.

 

[croissantking]

Some context:

With the Mac shut down, but plugged in and supplying +5V standby

- 5V 10mA is supplied to the D- lines at USB ports 1 and 2 through the transistors at Q9 and Q53.
- A resistor divider connected to 1IN+ and 2IN+ sets Vref (the reference voltage – in this case, 0.26V) for the LM393 comparator to use as a baseline.
- 0.65V is supplied at 1IN- and 2IN-, which is above Vref and therefore the comparator is inactive.
- 1OUT and 2OUT are close to 0V.

When someone presses the keyboard power key

– The power key connects one of the D- lines to ground.
- Depending on which USB port the keyboard is connected to, the voltage at the corresponding comparator input drops to 0V, below Vref.
- One side of the comparator becomes active and puts out 2.5V at the corresponding output.
- The whole circuit – and most importantly the pair of transistors at Q10 and Q11 – becomes active. Pin 24 of the CUDA chip is pulled low through Q10, signalling the Mac to turn on.

 

[Daniël]

Page 16 of the Gossamer DVT schematic details the soft power circuitry, if you want to verify things with that.

 

[croissantking]

Page 16 of the Gossamer DVT schematic details the soft power circuitry, if you want to verify things with that.

This is great, I didn’t know about these schematics. I thought you were about to show me that all my reverse engineering work was unnecessary but these are just for the logic board itself.

CooI to see the PERCH Connector pinout and confirm that the USB startup circuitry I’ve worked on interfaces with kbdSwitch and Trickle5V.

Some other interesting details in there too, such as ‘CLONE power supply support’ next to the schematics for the Mac/ATX supply jumper, and the sword and globus cruciger illustration (Gossamer’s Story…?). Also, we can see which pull-up and pull-down resistors connect to GRKLPLL0 and GRKLPLL1 which would allow us to set 100MHz bus operation.

 

[zefrenchtoon]

This is great, I didn’t know about these schematics. I thought you were about to show me that all my reverse engineering work was unnecessary but these are just for the logic board itself.

CooI to see the PERCH Connector pinout and confirm that the USB startup circuitry I’ve worked on interfaces with kbdSwitch and Trickle5V.

Some other interesting details in there too, such as ‘CLONE power supply support’ next to the schematics for the Mac/ATX supply jumper, and the sword and globus cruciger illustration (Gossamer’s Story…?). Also, we can see which pull-up and pull-down resistors connect to GRKLPLL0 and GRKLPLL1 which would allow us to set 100MHz bus operation.

what can we say about these schematics ...? ^^'

G3 B&W schematics

Hi crews, did anyone ever see the schematics for the Power Macintosh G3 B&W aka Yosemite? I was able to spot schematics for some Power Macintoshes on this forum. There is a page out here that offers schematics for PM G3 Beige and some G4 Macs as well. Unfortunately, no schematics for Yosemite...

68kmla.org

 

[croissantking]

what can we say about these schematics ...? ^^'

G3 B&W schematics

Hi crews, did anyone ever see the schematics for the Power Macintosh G3 B&W aka Yosemite? I was able to spot schematics for some Power Macintoshes on this forum. There is a page out here that offers schematics for PM G3 Beige and some G4 Macs as well. Unfortunately, no schematics for Yosemite...

68kmla.org

Haha!

Well, yes, it would have been convenient to have access to this before.

I find it interesting to see how Apple laid out the circuit diagram for the power-on circuit compared to how I’ve done it.

It seems there are optional diodes that can be stuffed for 'hysteresis', I wonder what effect that would have.