Mike's Hobby Blog

The Brain Board review in Juiced GS included a description of a bad 74LS244. I have had one other report of problems with the Brain Board in an Apple IIe. In that second case, I had that person send back his board, twice. Though I wasn’t able to reproduce the problem in my Apple IIe with his board, I tried two different repairs, the second of which seems to be successful. The first was a simple swap of the 74LS244, which helped, but didn’t completely eliminate the problem.

After further analysis, I determined that the grounding of the 74LS244 is less than optimal on the Brain Board and switching on of the 74LS244 causes a lot of noise on the ground. Apple boards that use a similar data bus driver circuit (Apple FW card & Super Serial) also exhibit this switching noise. The stock Brain Board is somewhat worse in this regard. I found that adding an additional ground wire on the 74LS244 reduces noise to levels lower than the Apple FW board and appears to solve the problem.

This intermittent operation is typically seen as random characters input while at the console prompt, while not actually typing on the keyboard. If you notice this problem, add a wire between the ground pin of the 74LS244 and the ground lead of the decoupling cap near the other end of the edge connector.

Here is an image of a board with the fix applied.

brainboard 74LS244 ground wire fix

One more word about this problem. Though I didn’t know of any issue with the ground, when laying out the production Brain Board, I considered shortening the ground connection to the 74LS244, running it across the center of the board, instead of the top. This change might have prevented this issue. However, I decided that, since, in several years of operation of the prototype “Brain Board”, I had seen no issues, that it was unnecessary. This is a case where the “if it ain’t broke, don’t fix it” approach, was the wrong approach. For now, the one wire fix will have to do. If I make another run of these boards, the ground trace will be widened and rerouted using the shortened path I considered before.

Also because of this issue, I’m going to have to make major changes to the layout of the protoboard that I have described earlier in this blog.

Peter Neubauer wrote up an excellent review of the Brain Board and it is printed the in September, 2011 edition of Juiced GS.

Check it out – done by one of the folks that picked a kit up up at K-fest.

http://www.ustream.tv/recorded/16320592

Ken Gagne was kind enough to take some Brain Boards out to K-fest and sold them at the vendor fair. Do to these extra K-Fest sales, I’ve now managed to cover my costs in producing the “Brain Board”. Thanks to everyone that has purchased one (or more) of these units.

Because I’ve covered my cost, and it might be interesting to some folks, I’m now releasing the source code for the Wozanium pack.

Also included, is a ROM file suitable for emulators, such as Virtual II. This allows you to run and debug Apple 1 software in the Apple II emulator environment. Just select the .ROM file as the ROM for your machine and reset your virtual machine. Just as in the Brain Board, right arrow will clear the screen. With Virtual II, you can download AIF files of A1 basic and assembly language programs and run them in your emulated Apple II, using the emulated cassette interface built into Virtual II. Note that this ROM version does not include the ACI driver at C100, so you must enter the Cassette driver by entering “D000R”, instead.

You can build the source with the 6502 DASM cross assembler.
Use the following command line:
“dasm a2a1emulv5_1.asm -DBLD4ROMBD=0 -DHUSTNBASIC=0 -oa2a1rbh.o -la2a1rbh.lst”

Included in this zip is

* a1basic-universal.asm – Apple 1 BASIC modified to run on Brainboard/Wozanium (note copyright at beginning of this file)
* COPYING.txt – GNU lincense for rest of Wozanium pack
* a2a1emulv5_1.asm – Wozanium source code
* a2a1emulv5_1.lst – Listing
* a2a1emulv5_1.o – Object file
* a2a1emulv5_1.rom – 12K rom file that can be used with A2 emulators, such as Virtual II.

Click a2a1emulv5_1.zip to download Version 5.1.

More about the Brain Board can be found at:
http://www.willegal.net/appleii/brainboard.htm

The only difference between version 5.0 and 5.1 is the power up screen. The original A1 had alternating “_” and “@” signs with the @ signs flashing. The @ signs actually disappeared during the flash off.

With version 5.0, I had the @ signs flashing between normal and inverse instead of completely disappearing. With version 5.1, this was fixed to have the @ signs disappear during flashing, like on the original Apple 1. I actually had it right on earlier versions, but made a change to dramatically improve initialization time in version 5.0 and created this discrepancy at that time.

I’ve been shipping 5.1 since 4/1/11, and have heard no reports of issues. In fact, other than the flashing @ signs, I haven’t heard of issues with any of the versions, other than someone verifying the memory corruption bug with 4.0, that I previously reported in my blog.

Because the difference is pretty small and does not affect operation in any way, I don’t intend on automatically shipping updated 5.1 PROMS to those who already have 5.0 PROMs. If you have version 5.0 you can request an update or if you have a PROM burner, I can send you an Intel hex file with the new image.

There are still a few people with version 4.0 that I owe an update to – I plan on shipping version 5.1 to you around the end of the month.

The design is frozen and ready for general shipments. I’m now accepting orders and will be shipping the first batch of Brain Boards tomorrow.

Send me an email, for ordering information.

The Brain Board/Wozanium pack web page is up and includes a link to the Beta Manual with has all kinds of information about the implementation. I have a little more to add, including an example downloadable driver that allows a user to control the machine through a super serial card.

I have had some good feedback from the Beta team. Several improvements have been made to the Wozanium firmware and will undergo testing this week. I plan on starting general shipments on 3/21/2011.

Cost for kits will be $59 with free shipping in USA and $10 shipping internationally. I also plan on offering built up units, once I get through any flurry of initial kit orders. Send me an email, if you have any questions.

I have shipped several Beta kits to some Mimeo builders who also have Apple IIs. Once I incorporate any feedback from the Beta Testers, I’ll open up for ordering. Hopefully this will take only a couple of weeks. My own testing of the production board has revealed no bugs.

In some ways, this is the most complex retro-project I have yet attempted. There was a pretty decent blue print for the Apple 1 and Apple II projects. The complexity involved making sure I didn’t overlook any of the content in the blue print and filling in a few blank pages. The Brain Board project involves creating a way to map the blue print from one fairly complex architecture into another. It also involves mapping the software systems along with the hardware systems. With the motherboard projects, the software was a given. A similar project was the PS/2 to ASCII keyboard adapter, but that mapping is much more constrained.

Several folks have suggested I take pre-orders for this project. Though demand on this project is hard to estimate, I think I have enough parts on hand to supply immediate demand and pre-orders are not necessary.

I have decided to classify this kit as a level 1 kit – it is very easy to build. If you can figure out which end of a chip has pin 1 and have a decent soldering iron, you should be able to build it. Here is a list of projects that I have offered with their skill levels.

1) Apple Cassette Interface (stocked), Brain Board (shipping soon)
2) PS/2 keyboard adapter (stocked)
3)
4) Apple 1 (stocked), Apple 2 rev 0 (discontinued)
5) Datanetics keyboard (several PCBs left)