Category Archives: A2 Proto Board

SCELBI TTY and Apple II Serial Card Update

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I now have SCELBI TTY cards in stock and will ship one to you for $30, shipping included. If you are interested send an email to: mike@willegal.net. Be aware that at this point they are not tested, so until I get one tested, I don’t guarantee that they will work without modification.

Regarding TTY card testing, I have been delayed because I didn’t have a current loop interface to test it against. Well that has been rectified, as I have the Apple II Serial Card that I mentioned in another post working (at least in RS232 mode). In order to get that card working in a way that would work for interfacing to the SCELBI TTY card, I had to reconstruct and burn a P9 PROM that matched the first version PROM. Wendell Sander was nice enough to send me a PROM that was a copy of his serial card P9 PROM. However, his P9 PROM was overwritten in a couple of spots with a all ones pattern. I took his PROM and compared the parts that were intact with the listing at the back of the manual and determined that I could resurrect his PROM by filling in the missing code with the code from the listing in the manual. After messing up my first attempt, I burned what I thought was a good P9 PROM. I put it in the Serial card and tested in RS232 mode against a Super Serial card in another Apple II. That simple test was successful and I now have a working Apple II Serial card without the undesirable flow control behaviors of the second version PROM.

I should be able to use this card in current loop mode for testing the SCELBI TTY card. In fact, I have visions of putting it in an APPPLE IIe (for the needed 72 column support) and emulating TTY operation as closely as I can with the Apple II. I should be able to emulate not only print and typing functions, but emulate paper tape as well. Potentially, I could even add a real paper tape reader and possibly punch by constucting an interface on a SUPERPROTO board.

As far as my prototype TTY card itself, it is mostly built up, just missing a couple of resistors which should arrive today or tomorrow. Once it’s together and tested I’ll put up a Bill of Materials, some simple build instructions and photos.

Apple II Serial Card Initialization Details

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While looking for a way to test the SCELBI current loop interface, I discovered that an early Apple II peripheral card, the Serial Interface Card, supported current loop. This card was designed to interface to printers and supported half duplex baud rates up to 19200 baud. Since I only need 2400 baud for SCELBI and the SCELBI only supports half duplex, I thought that I could use it for testing the SCELBI TTY interface card.

I found that I had a serial interface card in my stash and tried it out, using the RS232 mode to see if it would work. However I found that it would only output 1 byte and then hang. I had a friend who scanned the manual for me and sent a PDF to me. Looking over the manual at first, I couldn’t determine what was wrong. However dumping the firmware revealed that the firmware was different than that listed in the manual. After some web searches, I determined that there was a second version of the firmware that supported RTS/ACK software handshaking and that this second version did not work with some printers.

Since I couldn’t find a copy of the second version’s manual, this started me off on an reverse engineering investigation. This was a more difficult process than I first anticipated. Along the way I learned about some clever 6502 programming tricks, including a way to implement a primative 6502 skip instruction. I also have come up with a partly annotated listing that may be of interest to Apple II peripheral interface designers. This doc details some of the tricks involved in initializing Apple II interface cards. As the input and output functions are not of much interest, they are not well documented.
Apple Serial Interface Firmware

By the way, with the second version of firmware, there is no way to disable the RTS/ACK software handshake, so I’m going to have to find or make a copy of the first version firmware to test my SCELBI current loop interface.

Say Hi At VCFse in the Atlanta Area

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This year, for the third year in a row, I’ll be leaving the family in the care of our dog, Toby, and be spending a weekend with fellow retro-computer hobbyists. Since this years VCFeast, had to be cancelled, I’ll be treking down to VCF southeast in Atlanta for the weekend of April 20 and 21st. These weekends are always fun, so I highly encourage everyone that might be interested in these things to make the effort to join us.

Here is the link with informaiton for that event.
http://vintage.org/2013/southeast/

Stop by my exhibit. I’ll be operating a Mimeo 1 and a reproduction SCELBI 8H (one of a very few working SCELBIs in the world). I’ll even give you a chance to “drive”. Tell me you read my blog and get a free SCELBI/8008 reference card.

See you there…

Beginning of Year Retro Update

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Mimeo’s

Last weekend, I sold the last of the Mimeo PCBs (Glossy and Matte) that I had in stock. I will make some more matte after I’ve sold some of the first batch of the SCELBIs. I’m down to 4 ACI cards, so I’ll have to do a batch in matte to go with the next batch of Mimeos.

The new movie, “jOBS” will premiere at the Sundance Film festival this month. I’m hoping that the Mimeo PCBs that I sold to the prop house supporting the film, get some screen time and the film is good enough to get some decent reviews.

I still have plans to do a full built up system, but that project will have to wait until I have the SCELBI going. I am sorry that this has been teaser for some folks who have been waiting for it. However, I’m hoping that when I finally get to it, that folks will be impressed with the results, and say that the wait was worth it.

The new run of Datanetics PCBs have been trickling out, maybe a little faster than I expected, given the difficulty of finding components. They have mostly been combined with Mimeo PCB sales. I really wonder how many will get built up. This datanetics PCB batch has been done more of a service to the retro community, as it will be a while before this project breaks even financially.

SCELBI

Quotes from Advanced Circuits on SCELBI boards are about half of what I expected, which is awesome. Nashua Circuits came in as expected, so I guess Advanced will get this business, unless Nashua can do much better (I’ll give them a chance to improve their quotes). Since there is no solder mask, it really shouldn’t make much of a difference who makes them.

Design checks on the base 5 board set is done, and I’m about ready to declare victory on the layout tweaking/matching. The 8H backplane is just about ready, so I’ll probably get a batch of those made to go with the base 5 board 8H set, making it a 6 board set. The backplane has been challenging, as there is no schematic, only a wire list intended for wiring your own chassis. Good images of the top of backplane are non-existant. My orders for the PCBs may go in, as early as this week.

I do have one thing to check on the CPU board. There were at least two versions of the CPU board made, I am replicating a later version. There is a report of an issue with the step function reported SCELBI digest, issue II. Though describing a problem in a later version of the CPU board, this report shows a slightly different design than the one in the version of the schematics/layout that I am replicating. I just need to make sure the schematics that I’ve followed are accurate.

At this writing, estimates for the set of 6 PCBs, with an 8008D thrown in, but no other components, is in the range of 300 dollars. Final price might vary a bit, but I doubt that I could make it go any lower, without making this a one off effort, not to be repeated.

A friend of mine, is looking into doing a reproduction bezel for the front panel of the chassis. He tells me that there are some challenges, as the original was anodized, and most panel manufacturers, these days, do powder coating.

Today, I am going to see if I can generate a BOM (bill of materials) in an excell spreadsheet. Except for the 8008 and memory, I think most of the rest of the electronics components are readily available. I plan on sending the BOM to Unicorn, who have indicated, a while back, that they would do parts kits for this project, like they have for the Mimeo/Apple 1. The relay sockets used for I/O ports in the chassis, are available, but expensive – I’m going to see if I can find a way to get bulk price on those from someone.

The 8B will follow on the heals of the 8H, It uses the same front panel, CPU, DBB, and input boards as the 8H, but requires 4 new boards…

  • new backplane with an extra slot for the memory addressing board. I haven’t investigated in detail, but I hope I can leverage most of the 8H backplane design, making this pretty straightforward
  • new 4K memory module. I already have done the base chip placement for this one
  • PROM board. Cameron Cooper has a draft design, that he says he will let me leverage
  • memory address expansion card – haven’t started

    • All in all, you can see that based on the head start that I have on the 8B boards, this shouldn’t take nearly as long as the 8H has taken, to complete.

    After these are done, there is more SCELBI hardware to be done, a TTY interface, a scope interface and a cassette interface. Power supplies are another potential future project. For now you will need to find a 5 volt and -9 volt supplies. Amperage ratings depend upon the amount of memory and peripherals. According to SCELBI documentation, system with a keyboard, oscilloscope interface, and cassette interface requires the following.

  • 4K memory requires 5 volts at 6 AMPs and -9 volts at 3 AMPs
  • 1K memory requires 5 volts at 3 AMPs and -9 volts at 1 AMP

    • I’m also likely to do an automated front panel controller with a micro-controller, to make loading the memory on the 8H easier. I might be able to reuse my existing PS/2 adapter with a new program in order to accomplish this.

    Brain Board

    Brain Board stock is dwindling, but sales have been very slow, as of late. When the stock runs out, I’ll definitely hold off on making a new run, until demand builds up again.

    SUPERPROTO

    So far, interest has been a bit lighter than expected. However I’ve got wind of a couple of super cool SUPERPROTO based projects, that may just jumpstart sales when the projects are publicly announced. Feedback from folks using the card has been positive, with no unexpected problems or issues reported. I also know of one, well known, Apple II hardware designer that is leveraging parts of the design, which I have published in detail on the SUPERPROTO Wiki, for his next efforts. Even though, I get no financial reward from this leveraging, it is gratifying to know that my efforts are of use to others.

    Apple II rev 0

    A rerun of these PCBs is also in the cards, though I want to make a few tweaks, so it will also come after the SCELBI and probably the fully built Mimeo.

    That is all the retro stuff that I can think of, for now – Happy New Year

    More SUPERPROTO ideas

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    Prototypers looking to save money – check out the how I changed the 1101 SRAM tester into a permanent solution, without dedicating a SUPERPROTO board.

    http://willegal.net/superproto/index.php?title=Extending_to_Bread_Board_for_rapid_prototyping

    I also added jumper selection of SUPERPROTO superpages to my SUPERPROTO experimenters board. I’m able to change personalities of my SUPERPROTO now, simply by changing out the breadboard and by changing jumpers.

    New SUPERPROTO “Experiment” Added to Wiki

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    This is really a practical application, not an experiment. Follow this link to see the details of the 1101 256×1 bit SRAM tester that I put together.

    I bought a bunch of these SRAMs for my SCELBI project, and since it is going to be a while before I can actually use them, I wanted to get some kind of read about how good or bad this lot of chips was. I have the SUPERPROTO available, so I went to work and put this tester together in three days. Probably 3/4 of the time was spent writing and debugging the test program.

    Oh – except for the one I ruined by connecting -9 volts to an address pin, all the SRAMs I’ve tried so far, test good.

    SUPERPROTO Now Available

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    I’m going to open up general sales of SUPERPROTO kits and PCBs.

    Price will be $65 for a SUPERPROTO kit.

    Bare PCBs (no components) are going to be $35 each.
    I’m also offering a bundle deal of 4 bare PCBs (no components) for $125.

    Shipping will be a flat $10 to anywhere in the world. When I get busy, I often ship on Monday after packing during the weekend. Because of this, shipping may take up to a week after payment, though usually it’s less.

    For detailed ordering information, send an email to: mike@willegal.net.

    SUPERPROTO Update

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    Check out the new light detector experiment that I just posted on the SUPERPROTO wiki. http://willegal.net/superproto/index.php?title=Photo_Detector It actually took me about 3 times longer to write up this new wiki page, as it took me to try this experiment out. The SUPERPROTO is really going to make experimenting on the Apple II a snap.

    Thanks to Ken Gagne, I managed to sell a number of SUPERPROTOs at K’Fest. I also sold another to a person I know well. I expect to get some feedback with the next couple weeks, as well as get the few that did not sell at K’Fest returned to me. Assuming the feedback doesn’t reveal anything serious wrong with the design, I’ll be opening up general sales in about 2 weeks.

    Regular price is still to be set, but will not be lower than the special K’Fest introductory price of $60. I know that this is quite a bit for a “proto” board, but the PCB and chip costs dictate price, and there is little I can do about it. However I will offer bare boards at approximately half the kit price, for those that can supply their own 75LS245, GAL, VIA and EEPROM, or don’t need them for their application. I’ll also consider quantity deals for folks that want a batch of bare boards to use as the basis for a limited production project. Drop me an email at mike@willegal.net if you have interest in a quantity deal.

    Significant Updates to SUPERPROTO wiki

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    The reference section has been significantly improved with following topics added:

  • Power and Ground Planes
  • Prototype Area for ICs
  • General Purpose Prototype Areas
  • Apple II Bus Access
  • Extending to a Bread Board for rapid prototyping

    • I’m particularly excited about the breadboard section, as it opens up the Apple II to easy HW prototyping.

    SUPERPROTO connected to breadboard

    SUPERPROTO connected to breadboard

    A couple of years ago, James LittleJohn had offered a card (LittleProto II) with a breadboard built onto it. I think that the approach of a separate breadboard will allow you to easily work on your design, then when you feel that it is solid, move it permanently to the proto area on the card itself. In fact, Jon Titus had published a book back in the old days, that suggested a similar scheme for hardware interfacing. The book is called “Apple II Interfacing”. I talked to Jon about updating and releasing a modified version of this book a few months back, but at this point that project is in limbo.

    SUPERPROTOs will be at K’Fest

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    I sent 10 kits to the show – they will be priced at $60 each. One additional kit has been donated to the organizers as a prize/giveaway.

    Here is what the built up superproto looks like.

    SUPERPROTO

    SUPERPROTO

    More information is available on the SUPERPROTO wiki. This is currently a work in progress, as there are several areas that need more documentation. In particular is a description of how the copper layer in the proto areas is set up. It is kind of hard to see, since the solder mask tends to conceal the connections between the pads.

    I also need to add a page to show how to connect the SUPERPROTO to a separate breadboard for easy prototyping.

    More kits will be available in a few weeks, once I catch up on things.

    After the grounding issue with the Brain Board, I did as much research on grounding Apple II plug in cards, as I could. This included rereading some Apple Tech Notes on the topic, which were somewhat insightful, as well as examining existing designs.

    I really tried extra hard to make the ground plane on this board as good as I could make it, and still keep the 2 layer layout. The result exceeds my expectations, as the ground noise on the base SUPERPROTO card is almost non-existent. The 5 volt supply also received some attention, and it looks clean as well. In fact, the board looks much cleaner than my wire wrapped prototype, so I must have done something right.