Disk II interface updates

[mwillegal]

I have all the parts and etched the board this morning. Registration between layers isn't as good as I'd like, but it will do for a prototype. It will take another evening to drill holes and solder in the components. Some of you may wonder why I go through the effort of making a PCB for a prototype. Well I think a PCB results in a vastly more presentable finished board and I like the esthetics of it. The result should also be a little more reliable than the results of other prototype processes. I don't think that it is that much more trouble than say wirewrap or point to point prototyping. Finally, creating a prototype using the same artwork that a production house would use, makes going for a production run much less risky.

The board is designed to fit an a Serpac A20 enclosure, as used on my shutter tester project - http://www.willegal.net/light/tester.JPG. This is not the cheapest enclosure, but I think it is a pretty good looking off the shelf box. I'll have to come up with some kind of cool decal to put on top of it.

-Mike W.

PS In this image I haven't yet removed the ink from the laser printer image that is used to form the resist.

[mwillegal]

Quick update - holes drilled and components soldered in (except for AVR's, which go into sockets). Power supply checks out OK. I will be able to bring up USB and Disk interface sections separately. Communications between the two AVRs is through a serial interface and I have added a header which will allow me to interface from a RS232 port on a PC directly to each AVR, during initial bring-up. First, I intend on bringing up the Disk interface to state where I left it on original proto board. Some tweaks to the SW must be made because of change in AVR versions, but this shouldn't take very long. Once that is working, I'll bring up the USB interface. Finally I'll combine the two and work on host protocol, which is the last major activity planned for this project.

[mwillegal]

Disk section of new proto board checks out - I'm able to read/write/format disks with same functionality as the first proto board. Inner tracks don't seem to read quite as reliably as before, but I'll look at this later on. Using a crystal for clock seems to be a good thing, because the format function seems to fit a track a little better on to a disk. I couldn't tune that RC oscillator well enough to suite my liking.

Next step is the USB interface.

Regards,
Mike Willegal

[mwillegal]

Good, somewhat surprising news. I programmed the AVR that is being used for the USB interface and the device attached to a PC on first attempt. So far I haven't been able to get serial data through it, but just communicating with a PC is fantastic progress. Next steps...

1) Figure out where serial data is being lost
2) I'll plug in the Disk ][ interface AVR and get some basic operations working
3) I'll have to finalize and implement the host/Disk ][ communications protocol.

[mwillegal]

step 1, figuring out where the lost serial data went, is evolving into a complete investigation of the USB bus architecture and a relook at using CDC vrs Mass Storage device class and the V-USB(AVR-USB) implementation in general. The HW implementation is unlikely to change. This is likely to take some time.

[mwillegal]

Ok, did my deep dive of USB standards and think I have a handle on the technology.

I tweaked the code to make it look like a Mass Storage device using bulk only protocol to the host. The AVR handling the USB interface will simply transfer the USB mass storage commands/data/status between the AVR handling the disk interface and the USB bus.

So far the basic transfer is not working, but I think I have a good grounding on the technology, and now the process becomes a debug effort.

Stay tuned...

[mwillegal]

Great news: I finally got the USB interface working well enough to get a command down to the processor handling the Disk ][ interface. The PC even recognizes a mass storage device. Now I have to work on some code that will handle those commands - my original code used ASCII commands from a terminal. I should be able to make faster progress now.

[mwillegal]

No major progress this summer on the Disk ][ interface - too many distractions . The USB interface is pretty difficult, though I do have the Disk ][ interface recognized by a PC as a disk interface.

Beyond the usual family activities and homeowner maintenance projects, a few other projects have interfered, including constructing the microphone preamp that I needed to improve the quality of my podcast and research on the City Point and Army Line Railroad. I also just received good scans of an original Apple 1 circuit board, which may be the catalyst that kick starts an Apple 1 replica effort. Too many projects, not enough time .

[mwillegal]

Well a couple of things have come up to the front burner (Apple 1 replica) and I'm putting the Disk ][ interface project on "Official Hold" for the time being. I hope to get back to this, but it isn't going to be real soon.

If there is someone out there with solid HW/SW micro-controller experience that would like to help move this along, I'd be willing to share current state of the design with them. For starters, you got to be able to fabricate a board for your own use. Understanding of the Disk ][ technology and the USB interface are also important. If you feel that you have the know how and have the drive to take this somewhere, drop me a line.

Regards,
Mike Willegal

[mwillegal]

Future posts and this the current contents of this blog will be moved to http://www.willegal.net/blog/