ADB over Audio and USB lines of KVM+Audio Switch - Possibilties?

[Trash80toHP_Mini]

Curious about exploring the possibilities in general over the Audio's four wire connection which needs be rejected out of hand for lack of +5V. I'd earlier wondered if a USB KVM switch could be used to run ADB over the USB wiring, but @Gorgonops pointed out some reason or other that it was impossible. Now I'm curious about using a USB KVM+Audio Switch as the basis for an ADB KVM switch? I'm also wondering if USB +5V line would be compatible with ADB requirements? Between USB Power/ground and Audio's pair of signals +- Microphone there should be plenty of signal lines to do ADB?

Goal: design a PCB combining compatible assortment of KVM+Audio signals at the Mac end similar to the PS2 based MiniView Mac Converter:

View attachment 18325

Project would remove the manual ADB/Video KVM switchbox out of the picture entirely, with each Mac connected directly to a "MicroView" adapter and a modern USB KVM+Audio Switch like the four way unit I'm using now would replace the MiniView A/B PS/2 KVM. The only drawback I see ATM would be lack of connection to a "real" USB KVM, it would be an ADB Mac only bodge. Should the baseline project be workable, I'm sure adding a single USB to ADB Wombat solution will be workable, but that's for another thread.

https://old.pinouts.ru/Slots/apple_adb_pinout.shtml

https://pinouts.ru/HeadsetsHeadphones/

In simplest form, a Pair RCA jacks yield two signal lines and ground

https://pinoutguide.com/Audio-Video-Hardware/rca_connector_pinout.shtml

Dunno iv USB KVM+Audio would be +Microphone or not

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OK, I got carried away with the intro. :   So the original project/inspiration for the above had been relegated to IP tangent status. I have an Extron SW6 VGA Audio switchbox that has five lines available.



So of course I'm wondering about reduction of the switching circuits for audio to the least common denominator. Pulling ICs at one level or the other will probably be necessary to re-purpose one of the Audio ground lines as the +5V line of ADB.









I'm hoping it can be done at this level by pulling the INA137 AUDIO DIFFERENTIAL LINE RECEIVERS?

 

[beachycove]

I have a Alps-switch Mac adb keyboard connected via an imate adapter to a cluster of G5 and Intel Macs through a Dr Bott dvi/usb kvm. Works fine for me. You may be hacking, however, so may be after something other than simple use of a good keyboard, which is all I wanted.

 

[Trash80toHP_Mini]

I have the great MiniView/MiniView Mac Adapter/MacKVM diagrammed above for cross platform setup on the MacDisplayUnit, though it's only a manual switch on the Mac side. I have a great USB KVM Switch for my main workstation in the bedroom and anything on the hack hutch on the other side of the rack doesn't need to be KVM'd.

This project is aimed at folks who aren't lucky enough to have the things we do. I'm firing up Illustrator on the DA in a few. Diagrams are a must, as my explanations  .  .  .  don't. :mellow:

 

[Trash80toHP_Mini]

OK, maybe this clears away the mud?



ISTR USB's differential signally(?) to be the bugaboo? Clean signal lines for ADB and PSW might be available on the audio connections? If not, it'd be due to the USB+Audio KVM Switch having the likes of the mess in my Extron VGA/Audio switch?

 

[sfiera]

Wouldn’t this essentially amount to hotplugging ADB?

 

[Trash80toHP_Mini]

Speaking of the Extron Switch, the block diagram a DWG file that I haven't been able to open. Could someone download, convert to .PDF or .jpg and post it in this thread for me?

https://www.extron.com/download/files/blockdiag/SW6VGAAudio.zip

 

[Trash80toHP_Mini]

Wouldn’t this essentially amount to hotplugging ADB?

Nope, hotplugging is removing the connector by hand, which is definitely dangerous and can tear up an ADB Controller IC if done clumsily. A mechanical KVM switch takes the mishandling factor out of the transition, but is less than ideal. Digital logic switching it the real deal. Mac KVM Switches were made in both varieties way back in the olden days of ADB.

Macs can lose track of where/what ADB is doing when peripherals are switched in and out of circuit, but running ADB reset puts everything back in sync. It's usually the mouse that wigs out, so keeping an alias of ADB Reset on the desktop makes it as easy a few keystrokes to run it and set things aright again.

Edit: USB KVM Switching is done in digital logic in every case of which I'm aware. In the bit less olden days of long lived vestigial PS/2 connections, there were still mechanical KVM Switcboxes being made, IIRC. ISTR high end PS/2 KVM switches having a KBD emulator switched in and out of circuit in place of the physical KBD, however I've not seen anything alluding to such a necessity in ADB switching.

 

[Trash80toHP_Mini]

2013 thread about ADB KVMs:





.  .  .  a more technical thread from a year earlier:



Eight years ago the likes of the Big Tomato's USB-Wombat was but a dream!