Serial port for (early) New World Macs...

[paws]

Hello.

I've been poking around my Sawtooth and Lombard, and I just now noticed that the modem in them is identical.

I know that there existed boards for the PowerMac towers that added a serial port by replacing the modem and looking at pictures of the Stealth ports as well as the datasheets for the chips on the modem, it looks like a new board would be simple to make.

This interests me, since I've been learning to make PCBs and I would like a serial port on one of my Macs for an old MIDI interface. I'm wondering if anybody has the pinout for the connector on the motherboard.

(Actually, I'd love to see the schematics for any of these new-old Macs)

 

[techknight]

Might want to look at the developer notes of those particular machines. Starting with the Duo line, the serial interface to a modem module was taken away, and replaced with a datapump bus. So basically "half" the modem was on-board and "half" the modem was on a module. The modulator part. 

 

[Bunsen]

What's the difference between a datapump bus and a TTL serial line?

 

[paws]

The devnotes (found them on Preterhuman) unfortunately state quite bluntly that they don't contain the electrical or mechanical specifications. They do, however, say that the modem presents itself as a serial port that responds to the common AT commands, which fits with the fact that there's a two-chip set on board that includes microcontroller. It should be possible to reverse engineer the pinout from the modem datasheets, I was just hoping for a short cut - it's  a 70 pin connector and there is a lot on those boards..

 

[techknight]

What's the difference between a datapump bus and a TTL serial line?

datapump is some proprietary architecture to the RCV144K and other modem chipsets. 

 

[NJRoadfan]

The Sawtooth has a SCC on board, the header the modem plugs into is basically a serial port. There were a few aftermarket headers sold for these machines that replaced the modem with a true Localtalk compatible serial port.

http://www.geethree.com/stealth/install/g3viewa.html

http://www.geethree.com/stealth/install/g4viewa.html

 

[Bunsen]

That's true on the desktops, but not on the laptops.  When I find my Stealthport serial adapter, I'll have a close look at it with an eye to replication.

 

datapump is some proprietary architecture to the RCV144K and other modem chipsets. 

That's unfortunate.  Is there anywhere on the logic board upstream of the datapump where we could hijack a true TTL serial signal from?
 

 

[paws]

The modem chipset is two chips, a microcontroller and a... something else. The interface between them is called datapump, but here the modem has both chips. The modems I pulled from the Sawtooth and Lombard are actually identical, and the remarks in the devnotes are the same (that theyre serial devices that take AT commands).

The one in my (dead) Wallstreet is different, though.

 

[techknight]

Well if its true TTL serial it might be ok. 

Problem is though you may have to trick the ROM/OS and telling it that its a serial port instead of a modem. as serial devices wont talk to it thinking theres a modem there. 

For example, you wont be able to switch localtalk to a "modem" only a Serial port. 

 

[paws]

Didn't the Stealth ports require an extension? I imagine that's what that did, then.

Looking at the pictures in Bunsen's link, I am 99% certain it's just RS422 drivers or something equally simple (maybe the big one is for clock division). Also that the differences between the G3 and G4 versions are physical, depending on how to mount the actual port...

If anyone has one of those, a couple of high resolution photos would be wonderful.

 

[Anonymous Freak]

I have a Griffin gPort in my G4.  It's literally just a cable that goes from where the modem plug is on the logic board to a port where the RJ-11 jack was, ending in a standard Mac RS422 port.

Edit: Wrongity, wrong wrong.  First, it was in my B&W G3, second, it is more complicated than I remembered.  There's one little board that plugs in to the modem port on the logic board, then a simple ribbon cable between that and a more complicated board where the port on the back of the computer goes.  The IC is a National Semiconductor DS8925M LocalTalk chip.

I tried to scan it, but my scanners focal plane is "at the glass" only. So here are some iPhone photos:

 

[paws]

Thanks for that, that confirms my suspicions.

I don't have enough Mac towers to check compatibility, but I'll probably try to make one for my Sawtooth. I wonder if anybody else would be interested.

One thing that throws me off, though, is why Apple used a 70-pin connector for a serial port and power...

 

[paws]

Hey. Been working on something else for a bit when two of the GeeThree Stealth G4+ ports showed up for sale locally. Snagged 'em, and put one in my Sawtooth that runs 9.2.2. This works of course. Unfortunately I don't actually have a proper cable, must of lost them in the Great Disaster of '09 (left a bag of cables behind when I moved), but I've got a mini din-8 -> db9, and this works for talking to a Soekris board.

It also works in my 1GHz OS X-only G4 iMac, which is not on the compatible models list. I don't have a screwdriver small enough to remove the modem port here, so I've just got the cable running between the top and bottom parts. Hopefully there's a solution. One thing that's interesting is that the iMac modem board is the same connecter, but the actual modem is USB-based, so they must be using different pins for that. Do wonder what else is lurking on that connector!

I'd expect it to work in the Lombard as well, but there are obvious physical difficulties here too.

From pictures, the module in the G4 Mini is different, but it might actually be the same as the one for the G5s.

I hope to post a pinout soon for anyone not lucky enough to find real ones, it's plainly simple stuff

 

[paws]

The Lombard sees and talks to it fine, but it gets in the way of the keyboard so you can't actually reassemble it..

It'd definitely be possible to make one that fits, though, if anybody really wants a serial port in a Lombard or (I'd expect) Pismo.

Does anybody have any idea what the type/part number of the connector is?

 

[paws]

The USB modem from the iMac G4 shows up in my backup Gigabit Ethernet tower under OS X, so there is a USB connection of sorts on that header as far back as that.

It's a seventy pin connector, and handful of them are for serial, another two for USB...

 

[paws]

Welp - you snooze, you looze!

http://alexhixon.com/jamport/index.html

 

[Bolle]

That pricetag still seems to be a bit too much for me.

I would still like to build something like that on my own.