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Introducing (and interest check) CircuitTalk: LocalTalk for PowerMac G4

max1zzz

Well-known member
Very cool! I always wanted to get hold of one of these but could never find them at a sensible price...
Sign me up for one of the clones!
 

CircuitBored

Well-known member
I have acquired a PBG3 Pismo so consider it added to the "to be supported" list! Figuring out the rear panel port on this one is going to be a real challenge...
 

davidg5678

Well-known member
I have acquired a PBG3 Pismo so consider it added to the "to be supported" list! Figuring out the rear panel port on this one is going to be a real challenge...
Cool! It wouldn't surprise me if the modem on the iBook Clamshell is really similar to the Pismo, so maybe this could potentially work for several contemporary machines if we're lucky?
 

CircuitBored

Well-known member
Cool! It wouldn't surprise me if the modem on the iBook Clamshell is really similar to the Pismo, so maybe this could potentially work for several contemporary machines if we're lucky?

Both the Pismo and the Clamshell use the same main modem card as the desktop G4s. The main issue with my current design is that the IDC socket for the breakout cable is far too tall. I could easily add some alternate pads for a smaller connector, or alternatively just solder the smaller cable directly into the PCB. Either way there is not much vertical clearance to work with.
 

CircuitBored

Well-known member
For those who are really eager to get their hands on one of these: I now have five early-access boards available to buy!

This version of the board still has slightly mis-placed mounting holes but they are close to perfect. The electronics of the card are working perfectly.

These cards will not be provided with the requisite 10-pin IDC cable so you will have to source one of those yourself.

I can provide breakout boards for Sawtooth/Quicksilver or MDD. The MDD version has one screw hole out of alignment.

Ideally I would like these cards to go to folks who are planning to use them intensely or with a large variety of devices so I can get some data on potential compatibility issues and general performance.

£35 each. First come, first serve.

Postage will be priced per-buyer.
 
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CircuitBored

Well-known member
It turns out that my beta boards have fairly workable hole placement, I just hadn't reinstalled the standoffs properly in my testbench board. Here's what it looks like.

Tgm3oLm.jpeg


With this brain-fart identified I can call this beta board pretty much perfect! If you want an alpha board for bragging rights they are available too.

I'd like to get these cards out to a few folks before I order my first big batch so I can see how they get on with installing them.
 
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treellama

Active member
I can test in a Sawtooth and a QS, with P2P Localtalk, null modem, and a Roland SC-7. Dunno about intensive use though...
 

CircuitBored

Well-known member
I can test in a Sawtooth and a QS, with P2P Localtalk, null modem, and a Roland SC-7. Dunno about intensive use though...

Send me a message! I'm definitely interested to see if that Roland works. By all it accounts it should but you never know...
 

CircuitBored

Well-known member
A final post before I get a very late night: here is the final design for CircuitTalk G4. Let me know what you think!

ZSYV26R.png


One early-access board has been claimed and four remain!
 

ArmorAlley

Well-known member
don't even own a Mac Mini G4 yet and simply cannot afford one at the moment.
@CircuitBored I am prepared to send you (& give you) a Mac Mini G4 if you will send me one, should you ever get it finished. Let me know by PM.
I am all on for promoting this endeavour.
I've an used G3 modem card too that you are welcome to measure & study.
An ADB port on the back on the Mac Mini G4 would also be a wonderful thing. It would allow me to integrate the Mac Mini G4 into the ADB-KVM but I suppose I can use an iMate or BMoW Wombat for that. I would love to be able to turn on the Mac Mini G4 with an AEK II keyboard.
 
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CircuitBored

Well-known member
Here are some pictures of the external appearance of the MDD version.

oiEcCcV.jpeg


15yrWTh.jpeg


The serial cable fits perfectly into the hole originally meant for the "phone" connector.
 

CircuitBored

Well-known member
Minor update: I'm trying to remove the lower case of my iMac G4 so I can get started on prototyping but it just won't budge! With all four of the bolts removed there is still a great deal of resistance holding the bottom case in place. It feels almost like there's an invisible screw holding it down. I'm really baffled by what's going on here. If anyone has experienced an issue like this before then please lend me a hand with some advice! This machine has immense personal value to me so I really don't want to risk damaging it.

My current strategy is running the iMac at full tilt until it heats up a fair bit and then trying again. You never know...
 
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CircuitBored

Well-known member
My current strategy is running the iMac at full tilt until it heats up a fair bit and then trying again. You never know...

This worked a treat! Once it was warm the bottom came right off.

Creating a mini-DIN8 version of this modem breakout board is going to be... challenging. PCB drawing will commence tomorrow!

WGKEjgN.jpeg
 

CircuitBored

Well-known member
iMac update: It's alive!

AYVkQXb.jpeg

pr8n9E0.jpeg


The second image is how the machine looks with LT-Enet bridging set up and running. The MacIPPi is connected over ethernet, the PowerBook is connected to the serial port.

Everything is working perfectly on the OS 9 side of things but I had some trouble booting OS X with the card installed. I will investigate that and report back with what I find.

I am going to need some assistance getting a breakout board designed for the prior model of iMac G4. I have an EMC 1987 here and would specifically like to see the modem breakout from EMC 1873 as I believe it is quite different to the 1987 version.

There are only three early-access boards left now!
 
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