SCSI to Ethernet Adapter on New Hardware

[saybur]

I'm doing a revision of the hardware to add extra features and correct some bugs. @ronan also made good observations about things to fix, which is appreciated. Here's the list of what I'm working on:

• Move from KiCad 4 to KiCad 5, and change the footprints to match the awesome new library versions.
  
• Add USB for reprogramming & config updates (not sure if USB-C or just micro at this point, and I'm uncertain about powering via USB or leaving the barrel jack).
  
• Change the linear regulators to use more reasonable packaging, they're significantly oversized.
  
• Fix the oversized footprint on the barrel jack if it stays.
  
• Extend the board depth by 0.5mm to fit the case better, it tends to knock back and forth a bit.
  
• Shift the Ethernet / power plugs to get a bit more room on the back.
  
• (Possibly) add a jumper to use TERMPWR for board power.
  
• (Possibly) switch from the microSD socket to a full SD socket and upgrade the software to allow hot-plugging.
  

For anyone who has built one of these, were there other things you found annoying and/or features you thought were missing?

 

[ronan]

Fix the oversized footprint on the barrel jack if it stays.

You could manage to get power from USB, so you could easily remove the jack  

I also added a double DB25 port to be able to daisy chain the board, I used this one : https://www.digikey.fr/product-detail/fr/adam-tech/DPD-25-00-B3/2057-DPD-25-00-B3-ND/9833611

You can have a look at 68net repo for the footprint if you want  

Maybe you could also add mounting holes ?

 

[saybur]

You could manage to get power from USB, so you could easily remove the jack  

Definitely. My only concern with USB is the power negotiation step; I figure this board has a peak draw of ~950mA, including the terminator, which would exceed standard USB's 500mA. When you get into the higher power levels, AFAIK you have to actively negotiate with the supply, which is more complicated than just throwing a barrel jack on the board and calling it a day.

USB-C has the CC pins to indicate power availability, and I was considering going that route as an alternative. I've heard horror stories about bad USB-C cables, and I'm not 100% sure I understand the spec, but from what I can read it looks like an ADC input could detect the available power level and just refuse to start the terminator and/or other devices if insufficient power is available.

I also added a double DB25 port to be able to daisy chain the board, I used this one : https://www.digikey.fr/product-detail/fr/adam-tech/DPD-25-00-B3/2057-DPD-25-00-B3-ND/9833611

I think that's a great idea. The board is too short to add it at the moment, but I agree the feature would be nice for daisy-chaining.

Maybe you could also add mounting holes ?

The case I suggest (Hammond 1455L801) doesn't require them, but there is plenty of spare space along the edges kept clear for the PCB rails. I can probably sneak in mounting holes.

Thanks for the feedback!

 

[ronan]

Definitely. My only concern with USB is the power negotiation step; I figure this board has a peak draw of ~950mA, including the terminator, which would exceed standard USB's 500mA. When you get into the higher power levels, AFAIK you have to actively negotiate with the supply, which is more complicated than just throwing a barrel jack on the board and calling it a day.

You’re completely right. But I assume these are the official specs and that most usb wall chargers that are able to deliver 1A and more will deliver it without negotiations. (Maybe I’m mistaking ?)

 

[saybur]

No, I think you're right, from what I've heard most chargers (especially cheap ones) don't seem to follow the rules and just deliver +5V until they hit their limits (or Bad Things happen, the Big Clive YouTube videos on those things are hair-raising). I'm more concerned about plugging the board into a computer for programming, where the amount of power available is likely to be restricted to the USB spec.

 

[cheesestraws]

No, I think you're right, from what I've heard most chargers (especially cheap ones) don't seem to follow the rules and just deliver +5V until they hit their limits (or Bad Things happen, the Big Clive YouTube videos on those things are hair-raising).

I'm pretty sure the r-pi basically relies on this behaviour...

I'm more concerned about plugging the board into a computer for programming, where the amount of power available is likely to be restricted to the USB spec.

This is a good point IMO.  Personally, I'd probably leave both on, but allow for powering through the USB jack.  But this is a very uninformed opinion so feel free to disregard it

 

[Trash80toHP_Mini]

Loving the progress of a great project! Any chance of eventual reduction of the size to match a 2.5" HDD and adding thruholes for the headers outside those for the DB-25?

 

[saybur]

Loving the progress of a great project! Any chance of eventual reduction of the size to match a 2.5" HDD and adding thruholes for the headers outside those for the DB-25?

Thanks!

I'm not sure the circuit could fit into that form factor easily. What is the use case you're thinking of?

 

[saybur]

On the power side, after doing some more research I don't believe the USB-C approach will work easily. The ADC pins on the Xmega are all blocked in the current layout and I'm not keen on changing that if I can avoid it - it took quite a while to arrive at the current layout, I'm pretty happy with how things are, and it has been tested to work. There are some external ICs to support USB power but they seem to all be in hobbyist-unfriendly packages that would make this (already tricky) board harder to solder.

As for sourcing from TERMPWR, after doing the math I'm leery of doing that. This board draws considerable power for the non-termination components (possibly up to 380mA), which combined with a second active terminator on the bus could overload TERMPWR and potentially blow the Mac's fuse. Also, for the systems that supply TERMPWR, they should have a diode on the Mac which could possibly drop the line to ~4V or so; adding an additional diode to allow "auto-switching" between USB/barrel/etc could push the line so low it might not be able to provide enough headroom to let the 3.3V regulator operate properly.

There are two approaches I'm considering.

• Require the barrel jack, draw all power from it, and just hang the USB off the board as data only. This is the KISS approach and avoids problems with sketchy TERMPWR, USB silliness, etc.
  
• Alternately, move the terminator over to TERMPWR and use USB 100mA/500mA power for everything else. I would need to add enumeration support to the firmware, which is doable, and set things up to keep the peripherals in reset until the device is authorized to pull the higher power level or determines that it is attached to a dumb power brick.
  

I'd be interested in hearing if there might be another alternative I've overlooked, if anyone following along has thought of it.

 

[ronan]

The only other solution I see would be to design the board for internal use, and get power form the molex connector. But that would mean that people will have to mount the board inside tue Mac, and as you already chose a case I guess that’s a no go.

Btw it’s really interesting what you found about currents. I need to be careful with my board, and make I don’t blow the fuse....

 

[Trash80toHP_Mini]

Any chance of eventual reduction of the size to match a 2.5" HDD and adding thruholes for the headers outside those for the DB-25?

I'm not sure the circuit could fit into that form factor easily. What is the use case you're thinking of?

First off the, Duo 2300c, it has both SCSI and IDE cable availability for a 2.5" HDD so a new hardware board could be combined with an IDE to SD card. Also thinking about the PowerBook 150, but that would require bodged wiring to the HD-30's thruhole solder cones.

One suggestion to consider would be doing a riff on the PB FDD form factor. You could take power off the FDD cable. Position the Micro-USB connector at the door and provide for a printed case plug-in WiFi antenna housing to make a slight bulge out the side next to it. That could be so much smaller than the French TeleCom adaptation. Lots of Room in that FDD cubic, but cabling is again the sticky point for PowerBooks, however that form factor will handily fit inside any Mac.

You could print and paint the removable WiFi antenna bulge to look like a partially ejected floppy with USB on the side for PowerBooks and desktop Macs.

I've been wondering if a thin adapter PCB to be soldered over HD-30 pins and running underneath the logic board of a PowerBook to the FDD bay might be workable? It's a nicely spaced rectangular .1/.05 pitch combo grid. With WiFi, you don't need FDD Eggroll. [}]

/silly notion mode

 

[sutekh]

I'm not sure the circuit could fit into that form factor easily. What is the use case you're thinking of?

+1 for TRS80's suggestion. It'd be awesome to see something SCSI connected in a 2.5" form-factor for use in any Powerbook that could do double duty as an HDD replacement and provide wifi ethernet. 

#pipedream

 

[saybur]

Ah, I get what you guys are aiming for. Just to explore the concept:

It looks like a 2.5" HDD is about 100x70mm, which is basically the same size as this board, so the circuit could probably still fit OK. You'd want to keep the base SCSI interface and SD card, but rip out the ENC28J60 and replace it with some kind of wireless access device. That part might be problematic; the ESP8266 type devices have their own TCP/IP stacks, but the Nuvolink protocol assumes lower-level access to the network. It looks like some people have figured out how to make the ESP8266 enter promiscuous mode and work with raw packets, but both that and WiFi framing in general is not in my wheelhouse.

Assuming you could get the hardware put together, there would be a bunch of firmware work that would also need to be done. From the scuznet base, you'd need to rip out enc.c and net.c at minimum and replace them with something suitable for talking to the wireless controller. You would also likely need to develop some kind of Mac utility that could send wireless control information to order the WiFi device to associate with the correct network and that kind of thing, unless it was programmed in the firmware somehow.

It seems like an interesting idea, but I'd consider it to be out-of-scope for this project. If someone wanted to tackle it, hopefully the work done here would at least make their lives easier.

 

[Trash80toHP_Mini]

I just toss my crazy notions out there to see what happens. Unfortunately, this stuff is way above my pay grade, so I'm hoping someone will run with that project as you suggested.

 

[Chopsticks]

could you add a 50pin IDC header behind the 25pin sub connector? im sure there's a few people who would like to install this internally (myself included)

also a 2pin header footprint next to the D3 led to allow the option on wiring up a led rather then soldering a smt led... keep the smt footprint though, but just gives the option for an external led to be mounted say where the se/30 hdd led goes (hope that makes sense)

 Im not sure if would work well or not but perhaps some m3 mounting holes on the board could be useful as well

also a pinheaded to enable or disable the power going to the resistor networks could be handy to allow easy enable/disable of the termination would be quite Handy too

 

[Chopsticks]

btw im also wondering is anyone has had issues enabling appletalk on the se/30, its probably an issue with my Mac but with apple talk disabled everything runs fine and I can say use fetch to download some files from my server but if I turn on appletalk it hangs during boot if the ethernet it plugged in... I was just hoping to confirm from anyone else here that has this running with an se/30 as I suspect I either have a bizarre fault on my logic board or there's something going on with the driver that needs to be modified. ive tried sys 7.0.1, 7.1, 7.5.3, 7.5.5 with and without open transport v1.3 installed and get the same issues.

I noticed in the driver resource using resedit that there are specific drivers for a few Mac models suck as the MacII, macPlus ect so before I just down a rabbit hole I just wanted to check here first.

worth noting if I use it with my Mac Iici logicboard then appletalk works and can connect to my A2Server without any issues..

 

 

[karrots]

There are some external ICs to support USB power but they seem to all be in hobbyist-unfriendly packages that would make this (already tricky) board harder to solder.

You could just leave a space for the many pre built modules out there. Here is an example.

https://a.aliexpress.com/_mNPE3bn

 

[Michael_b]

Finally got my scuznet board assembled. To my great surprise, it worked on first boot - booted straight into 7.5.5 on an SE/30! Tomorrow, networking...

 

[Trash80toHP_Mini]

Fabulous, great news and congratulations. I love to see progress being made on what seems to be all fronts,

 

[aliban]

Any advance on the disk management part of the card?  Thinking on building one.