First, a little background.

About a month ago, Rich Dreher tipped me off to an EEPROM issue he had seen in the past when interfacing an EEPROM to the Apple II bus. Well I didn’t have any issues with my prototype unit, but decided to do some additional testing with different EEPROMs. Back in the lab this EEPROM testing got confused with a flakey motherboard issue and the whole thing set me back a month.

After moving to a different motherboard, I eventually figured out that ATMEL EEPROMs don’t play well with the Apple II address bus, just like Rich indicated. However, an alternate source, XICOR, makes EEPROMs that do seem to behave quite well, so I’m back on track. During initial bringup, I had done my original testing with XICOR, which is why I didn’t see the problem with ATMEL parts.

So besides checking out EEPROM behavior, I made some design tweaks, checked out bus timing, made sure interrupts work and so on. At this point everything looks good,so I just pulled the trigger on a small trial run of boards. With any luck I may even manage to get some sent out to those of you HW hackers that are visiting K-Fest.

I plan on completely documenting this board including the GAL online, so little to no printed documentation will be created. If I can figure out how to do it, I want to set up a wiki type documentation environment where prototypers can add their own designs and share their knowledge with everyone else.

Here is the top side layout:

The base feature set includes

Onboard 32K EEPROM – only 2K is normally addressable from Apple’s C800-CEFF and CX00-CXFF I/O space

EEPROM is programmable directly from the Apple II’s 6502.

Glue logic integrated in 22V10 GAL – replaces a number of 74LS glue chips that are commonly seen in designs like the super serial card and the mockingboard

Data bus fully buffered with 74LS245

PCB location for 6522A VIA, with no additional glue logic required

Two general purpose proto areas

Locations for more than 5 300 mill DIP chips of varying pin count

With 6522 VIA, room for an additional 40 pin dip package. This does cut into 300 mill DIP area. but it should be possible build a 3 channel Mockingboard on the super proto board.

Synthesized psuedo PH2 clock available – was required for 6522 inteface

The hope is that this board takes care of all the heavy lifting of interfacing to the Apple II bus and lets you focus on the the fun side of hardware hacking on the Apple II.

Pricing hasn’t been set, but it will be well under $100 for a kit. Bare boards will also be available.

Stay tuned.

I use a GAL to reduce part count in this design. I’ve had a terrible time programming the GAL with a vintage Data I/O 29B and finally gave up and bought a cheap chinese programmer that seems to work better.

After a few tweaks, especially surrounding the difficult timing on the 6522 VIA, I have the prototype up and running and even blinking a LED. I found an Apple tech note about interfacing to the 6522 that I decided to follow exactly. I had one other issue with handling the release of the selection of the C800-CFFF ram space. Some of the schematics I found online, use some inverters and a cap to slow down response to releasing the selection, presumably to ignore glitches. I found that using the same delayed clock to condition this signal as is used by the 6522 interface, seems to work as well.

I implemented the PROM on this device with an EEPROM and I have been able to write some small test programs and save them in EEPROM without any need for a prom programmer. I think experimenters are going to love this feature. I wish I had done this on the Brain Board, but I didn’t think of it at the time.

For Apple 1 lovers, note that I did a quick checkout in a Brain Board/Wozanium environment this morning and had no issues.

I have lots of ideas for projects and it will be easy to connect it to a solderless breadboard for quck and easy prototyping. Besides use for experienced hackers, I want to make this a tool for people who want to learn fundamentals of computer interfacing and hope I can find time to do a series of introductory projects. What it ends up doing, besides blinking a LED, and the projects I come up with, is up to the creative people in the Apple II community.

I’ll definitely bring the prototype to TCF east next month. I’ll have to figure out how much more testing is required before ordering a batch of boards. I’ll definitely try it in my IIe, but what else I run it in remains to be seen. The PCB layout has been tracking changes made in the prototype, so once I decide I have a good final design, it will not take long to get the boards made.

After an email exchange with Vince Briel where Vince casually indicated that the A2 community really needs a prototyping board, I’ve decided to raise priority and get a batch of these prototype cards built.

I’m a little concerned about timing, especially with the 6522. The Mockingbird board, which also uses the 6522, does some strange stuff with clock timing and I need to really investigate what is going on with a real board. So, before doing the production build, I need to get a prototype proto board working.

Normally, I would just etch a prototype PCB at home, but a proto card needs a bunch of holes drilled in it which would take a long time to do manually and besides, I might need to make some significant changes, which is easy to do with wirewrap. In addition I had on hand an Apple Hobbyboard, which is ideal for this project. The Hobbyboard had been used before for a simple temperature sensor project that I did in the 80’s, but the old circuit had been removed from the board a few years ago. So in the last week, I have wirewrapped the new circuit onto the old Hobbyboard.

I haven’t gone very far in debugging because I keep frying the 16V8 GAL chips I’m using to cut down on chip count (and leave more prototyping space). Could be something to do with the ancient Data I/O Pal programmer I”m using. Anyway, there is real progress being made on this project and I hope to get things squared away so I can make a build this spring or summer.

This PCB layout is now in it’s fifth major revision and counting. Here is how it’s evolved.

1) A direct copy of Apple’s Hobbyboard. Many years ago, I used one of these cards to build an A/D interface with temperature sensor. This layout is ideal for prototyping with wire-wrap technology, but not so good for point to point wiring, which I prefer these days. So I moved on.

2) A direct copy of a Quality Resarch Company (QRC) Apple 2 computer prototype board. I used one of these a few years ago to build a prototype shutter tester. This board is ideal for point to point wiring, but I have decided it would be neat to build into the layout some basic I/O components like space for a 2K PROM and data bus transceivers.

3) This led to the first of my own designs. I incorporated space for a bus transceiver, a 27C256 EPROM, a SPDT switch and a DB 9 connector in this one. I used the 27C256 instead of a 27C16 because they are easier to find and cheaper, despite the fact that it has 16 times as much memory than is really needed. However, the handing of the I/O strobe for the 2K memory exansion space is kind of messy. On Apple’s super serial card, it takes 4 74LSXX series chips. This would require a lot of wiring and take up a big piece of the proto area. For these reasons, I decided to put this logic in a PAL or GAL and include the wiring right on the proto board, which leads to my next design.

4) In this version, I removed the toggle switch, thinking that it was not really that useful an idea. I was thinking I wanted the capability of interfacing an AVR micro-controller, while some other folks thought that a design that supported classic chip would be more appropriate. The 6522 VIA is a classic 6502 family part and includes some neat features including built in timers. I also switched from using a 27C256 to 28C256 flash part, so that it could be programmed in place, without the need for a PROM programmer. All along, I’ve wanted the capability of supporting that AVR on this board, but supporting both a micro-controller and a VIA seemed kind of awkward on the same layout.

5) My current layout tweaks the previous by making the half of the 6522 that is used for input/output pins a little more generic. The 6522 will still drop right in, but if something different is desired, then you just need to connect the bus interface to the proto area the way you want it. It is fortunate that the 6522 was set up with the I/O ports on one side of the chip and the bus interface on the other. In some ways, the 6522 VIA bus interface is just about an ideal generic A2 interface device. You have the system clock, the device select signal, read/write, interrupt, the data bus, and the four address lines that will address all 16 locations in the device select region of each slot. If you need some other bus signal, it can always be picked up off of the pads near the edge connector. One of my next challenges is to see if I can interface an AVR micro-controller directly to this bus, without additional components.

This design is not done evolving, but at this point, I think I’m happy with most of the major design decisions. I have plenty of FLASH memory for the program, a 6522 VIA for hardware interfacing and DB-9 for connection to the external world. With the 6522 in place, I have space for 4 16 pin chips, an 8 pin chip and plenty of discrete components. Yet the 6522 could easily be replaced by something else, like the AVR I keep thinking about.

One thing that might change is the DB-9, which takes up a lot of real estate. A KK type header like the one used on the super serial card is likely to replace it.

If you have ideas or opinions on this hobbycard design be sure to let me know. The more input I get, the better this card is likely to become.

here are scans of all eight pages. Someday maybe I’ll find time to OCR and put it into PDF format.

Here is another project that I am considering.

This is the beginnings of a layout replicating an original Apple 2 Hobbyboard.  This is a prototyping board intended for creating your own Apple II expansion card.

I’m thinking of building a batch of  either exact replicas or possibly modified with some improvements that I have in mind. This board layout is ideal for wirewrap applications, but I’ve moved beyond wirewrap a few years ago, so I’m likely to modify it for point to point wiring.

I’m also thinking of putting together some project kits that could be implemented on this board.  Projects I have done already that could be easily adapted, include my shutter tester and the improved firmware card.   I have other ideas like a spectrum analyzer for audio frequencies.

Let me know what you think and if you have ideas for projects for this hobby board.  Also if you have ideas for what features you would like to see in a prototyping board, let me know.