Now for the question – should I call my Apple II rev 0 reproductions Mimeo IIs, even though they came first?
Archive for the ‘A2 Proto Board’ Category
For those of you without soldering/rework skills, depending upon interest, I may do a run of reproductions, but it’s not going to happen for quite a while as I have too many projects already in the works.
I’ll try to find time to do a video blog of a Swyft card in operation, but don’t know when I’ll find time, might be today, might be three months from now.
I just finished turning one of my SUPERPROTO prototyping cards into a Swyft card. If you don’t know what a Swyft card is, Jeff Raskin was working on a low cost “appliance” computer called the Macintosh at Apple. Steve Jobs took over the project and moved the project in a quite different direction. Jeff left Apple and founded a company called “Information Appliance”. The first product was the Swyft card that plugged into an Apple IIe and ran his software. The software was an integrated word processor and calculator, which had access to Applesoft and included a few other printing and communications capabilities. Later they came out with the Swyft computer which was later licensed to Canon – which called it the Canon Cat. I didn’t explore functionality that much, but the software looks pretty clever, despite the lack of a GUI. 🙂
Once I get the rework instructions up on my SUPERPROTO Wiki, I’ll offer SUPERPROTO swyft card kits, with the components necessary to build your own SWYFT card, including preprogrammed GAL and EEPROM at the usual SUPERPROTO price of $65. The conversion of a SUPERPROTO to SWYFT card does require good soldering/rework skills, as you have to cut some traces and solder a few wires directly to pins on the back of the card. If there is enough interest, I could possibly make dedicated reproduction swyft cards.
By the way, this was another one of those projects, where I didn’t have to buy a single part, everything needed was on hand, either part of an existing kit or in my spares bins.
Here is a summary of status of kits and PCB availability
email: email@example.com if you have any questions
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: firstname.lastname@example.org. 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.
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.
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.
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…
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.
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…
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.
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 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.
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
Prototypers looking to save money – check out the how I changed the 1101 SRAM tester into a permanent solution, without dedicating a SUPERPROTO board.
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.
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.