Category Archives: Apple II

About Early Apple II computers

Improved Apple Teletype Emulation

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A previous post showed how I attempted to connect the SCELBI TTY to an Apple IIe with an old serial card that supported current loop. Well I’ve been working on some of the issues and now have it working good enough to post some of the details. With the standard Apple 80 column scroll routine, I can only reliably get 8 lines to scroll at 110 baud, but it’s working pretty decently, with that limitation.

First of all, here is how the TTY card is connected. The standard SCELBI MEA software assumes these port assignments.

Apple Serial To SCELBI TTY Connection Diagram

Apple Serial To SCELBI TTY Connection Diagram

If you try repeating this experiment, be aware that there are two versions of the Apple Serial Card firmware,. However, since I don’t use the standard driver, it doesn’t matter which version you have.

The simple TTY emulation source code can be downloaded from www.willegal.net/appleii/ttyemul.asm. It is written to use an assembler called DASM, which can be found and downloaded with a web search.

You can experiment with changing the window size by changing the second line in the program. Note that I started with a “hijacked” version of the original serial card driver, but it has been greatly modified. This code assumes a IIe with 80 column card. For display, I had a lot of issues getting CR not to send a LF, but still return to beginning of the line. I also implemented a bare bones bell that sounds only if no characters are coming in.

I suppose a custom “fast” scroll routine might help with increasing the window size, but I haven’t had time to work on that. I think I left enough of the original Apple II peripheral card software mechanism in place, that it wouldn’t be too hard to move the code to PROMs that would reside on the serial card itself. For now, it assumes slot 2 for the serial card, and slot 3 for the 80 column card. Let me know if you have any luck with this.

I’m using a modified version of this software as the basis for my Apple II RTTY software, but the transmit side of that implementation needs some work. I want to create a way to type in some canned strings for transmitting CQ with a call sign and so forth.

Video Posted Showing RTTY RX with Vintage Gear

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Check out my latest podcast.

feed://www.willegal.net/feed.xml

The Radio Teletype receive function seems to be working real well. The work I did in the “lab” preparing for this, resulted in almost immediate success upon hooking up my rig to a real HAM receiver.

Before I can start transmitting over the airwaves, I still have to do some work with antenna tuning, write an Apple IIe RTTY transmit driver and generally check things out in the lab. I also have some kludged cabling going on that needs to be fixed.

That said, I think that KC1CKV will soon be on the air…

73

HAL ST-6 RTTY TU Restored to Operating Order

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In a previous post, I showed a picture of my HAL ST-6 RTTY Terminal Unit.

Now that I had the SCELBI 8B working, in my spare time, I have devoted a few hours to getting the ST-6 up and operating. For those of you who aren’t aware, an ST-6, demodulates a Radio Teletype (RTTY) signal and presents a current loop data stream to an external device. It was intended for connection to a Teletype, but I’m connecting it to my vintage computers.

The HAL ST-6 is quite a different beast, as compared to the computers I’ve been working with over the years. There is a lot of hand wiring in it, and each module is filled with discrete components along with a few op-amps.

inside the HAL ST-6

inside the HAL ST-6

The RTTY signal comes in several forms. My mid 70’s era HAL ST-6 was designed to support demodulating a signal with frequency shift keying offset of 170, 425 or 850 Hertz. Instead of a teletype, my plans are to have a vintage computer decode the serial stream and display the incoming data. I’m starting with an Apple IIe and have written a driver for the old serial printer board that supports current loop. The driver reads 45.45 baud 5 bit BAUDET format, converts it to ASCII, and displays it on the screen. Eventually I hope to be able to port this code over to a SCELBI.

For testing purposes, I’m using an internet RTTY audio stream. This audio is routed from a computer speaker output to the HAL ST-6 audio input. This audio stream replaces the radio’s audio output of a real RTTY stream, which would normally come from the speaker output of the radio. At this point, except for a few quirks with my Apple II software, it seems to be working quite nicely. Once I get the kinks worked out of the software, I’ll hook it up to my radio, and see if I can tune in some real RTTY broadcasts.

RTTY tuning in the old days was enhanced by hooking an oscilloscope in XY mode to the oscilloscope output of the ST-6. I have done the same with this test stream and think I have a pretty good pattern.

RTTY eye pattern

RTTY eye pattern

Getting the HAL ST-6 up and running wasn’t trouble free. At first, the output of the 170 Hertz filter/limiter wasn’t working at all. It took quite a bit of debugging before I discovered that a potentiometer case was shorted against the windings of a coil. While debugging this issue, I found and repaired a broken wire on another coil. I also tweaked the “alignment” and spent considerable time just checking out the circuit to make sure everything was working correctly. I also spent a lot of time chasing “issues” that turned out to be operator error, but I learned a lot in the process.

Once I get reception working well, and get a handle on how real operations work on HAM RTTY, I’ll start working on the transmit side of things. This HAL ST-6 has an audio FSK modulator incorporated in it. I’ll have to be cautious about how I bring it up, since AFSK operations are well known to have a lot a issues with harmonics and spurious noise.

Apple PROM board, MEA/Apple TTY emulation update

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The SCELBI PROM board is working fine and I was able to create a small program in the editor and execute pass one of the assembler with MEA. I can’t completely assemble a program and run it until I get the cassette interface built and operating. Pass two of the assembler writes the output to cassette tape. I’ll have to hold up doing a video until I can get the complete package going. My impressions of the MEA package are quite positive. It’s not as elegant as later software you might be more used to. However, considering the time frame it was made and the platform is the 8008, it’s a pretty nice package.

SCELBI PROM and extra SRAM boards cost $50 each and are available now. This recent work also confirms that the TTY board is working fine and those are available for $30.

I’ve been using an Apple IIe in 80 column mode with a bit-banged serial serial card to act as TTY emulator. However there are a couple of fairly significant issues that need to be solved before publishing this teletype replacement solution. It’s usable for me, but there are some problems. The two issues with my current Apple II TTY emulation solution are:

  • 1)The Apple II isn’t fast enough to scroll it’s screen at the same time it’s receiving data in a bit banged mode. It drops a few bits from the next character while scrolling the screen. This means that I’ll need to come up with a special designed card to support 110baud current loop with a UART. Since I’m doing a new card, I’ll consider figuring out how to add paper tape support and possibly printer support, as well.
  • 2) In 80 column mode, the screen driver doesn’t support carriage return, without also doing a line feed. In other words, you can’t move the cursor backwards to position 0 on the same line, like a real TTY would when it receives a CR. I’ll have to look into a software fix for this, but it might take sending the cursor to home and then moving it back down to the correct position on the page or something like that.
    • SCELBI running MEA

    SCELBI running MEA

    This image shows the Apple IIe acting as a TTY for the SCLEBI 8B on the left. The screen contains a small program entered with the MEA editor. The listing of the program at the top of the screen has two extra lines at the end. The “D 000 006,000 007” is an editor command that deletes lines 6 and 7. The “L” command lists the text buffer. The last two commands “P1” and “P2” are pass 1 and pass 2 of the assembler. Pass 1 shows no errors. Pass 2 writes results to cassette tape. Since the cassette isn’t installed in my system it actually does nothing. If I had a tape, pass 3 would read the object back into the system so it could be executed.

    The “E”s on the left side of the screen should be the first character of the next line, but the Apple IIe can’t scroll fast enough to be ready to receive the first character of the new line, so it receives a partial character.

    yeah – MEA running on reproduction SCELBI 8B

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    MEA dump memory command - Apple IIe used as TTY emulator connected to reproduction SCELBI 8B

    MEA dump memory command – Apple IIe used as TTY emulator connected to reproduction SCELBI 8B

    Here is the dump of memory from the SCELBI PROM card from addresses 060-000 to 0600-037 as displayed on a 40 column Apple IIe, running some very simple TTY emulation software.

    To interface to the SCELBI, I’m using an Apple IIe with an old serial interface card. The Apple Serial Card is the first serial card released by Apple, and was intended to connect to serial printers. It included support for current loop and 110 baud rate. It’s the only thing I own, that supports that combination of baud rates and interface protocols. Be aware that this card is not the same as the very common Apple Super Serial card, which does not support current loop.

    For TTY terminal emulation purposes, I’m doing a major rewrite to the driver, as the default printer driver is not suitable for TTY emulation. I’ll post the emulation software and directions on connecting this serial card to the SCELBI TTY card as soon as I clean up a number of small issues.

    More updates on this exciting development to come soon.

    SCELBI PROM Board Progress

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    SCELBI PROM Board

    SCELBI PROM Board

    The PROM Board is built, installed and appears to be running. However, it’s not completely checked out. I need to hack together a simple Apple IIe TTY emulation program that will work with Apple’s old serial card. That card is the only card that I have (outside of my SCELBI stuff) that will run at 110 baud, but it was designed for printing, so I couldn’t find any ready made terminal program for it. The standard PROMs on the SCELBI 8B assume either a keyboard/oscilloscope interface or a TTY interface at 110 baud. Since we don’t have the keyboard/oscilloscope software, I burnt the TTY software into PROMs.

    It should take me a day to two to complete the TTY/terminal program hack for the Apple II, at which point, I will probably make short video showing the capabilities of the SCELBI 8B minus the cassette interface.

    I used black tape to cover the windows on the EPROMs because I’m told that sunlight will erase them after a while.

    Meanwhile, you can run the software in my OS/X emulator by downloading the MEA hex file from scelbi.com and jumping to 060-000. In a quick trial, it appeared to work ok for me. Be aware that I don’t currently have the cassette interface emulated, so cassette operations will not work. Cassette emulation is one the things on my to do list.

    Brain Board Inventory Down to Two Kits

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    I have two Brain Board Kits left and don’t think I’ll do a rerun anytime in the near future.

    I had a total of 59 made in early 2011 and it’s taken a while to sell the last few kits after a fair level of initial interest. Given the numbers made, these are likely to be hard to come by in the future. If you don’t already have one, this may be your last opportunity to get one for some time.

    Bob Bishop’s Apple 1 Trade In Deal – and just when did Apple II’s first ship

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    Apple 1 and Apple II programmer, Bob Bishop recently passed away. Though I didn’t know Bob Bishop, I did exchange a few emails with him in June of 2013. From the few emails I exchanged with him, I got the impression that Bob was a good guy, and I feel it’s unfortunate that I never got to meet him in person.

    Back in June of 2013, while refining the Apple 1 Registry, I noticed that at one time, that Bob had an Apple 1. I sent him an email, asking if he still had his unit. Bob replied, saying that he had traded it in. This was about the time that Fred Hatfield’s Apple 1 was sold at auction. There was much in the press about Fred’s Apple 1, which included a letter from Jobs, offering a trade in deal. This was a deal which Fred had refused. Bob was a little concerned that the trade he made, wasn’t as good as what Fred and others were offered.

    Here is the story of that trade in, in Bob’s words. The article he mentions, was a New York Times article that included some mention about how aggressively Apple pursued the Apple 1 trade in program.

    When I read that article, I was a little upset (and said so on my weekly radio show) to discover that the company had “an aggressive trade-in program, offering Apple II’s and sometimes cash incentives in exchange for Apple-1’s.” When I wanted to do MY trade-in, I had to go to apple and ask THEM if they would be willing to do it. They said YES… but only if I paid THEM some additional money! But I guess that was before they had fully started their trade-in program. So it may be that I have the dubious distinction of having been the very first person to trade-in my Apple-I for an Apple-II (since the serial no. of the Apple-II that I got was 0013). 🙂

    But now that you’ve showed me the original letter from Fred, It looks like the NY Times article may have gotten their information a little mixed up. According to the letter, it appears that Fred had to pay THEM the $400 — and not the other way around (just as in my case).

    I don’t remember exactly how much I had to pay when I made my trade-in, but I think it was about the same amount ($400). And I made the trade-in around late June of 1977, but Apple didn’t ship the computer to me until July. (I remember that they said it would be delivered to my home in the next few days. So on July third, I sat around anxiously waiting for delivey. The next day was going to be the Fourth of July, and if it didn’t come today, I would have to wait two more days to get it! Well, it didn’t come… so I had a very miserable Fourth of July that year. But around 10AM on July fifth, it finally arrived! 🙂

    – Bob –

    By the way, surviving evidence indicates that though Apple 1 trade ins occurred, it wasn’t a real great deal. Several surviving Apple 1’s that came through the hands of early Apple employees, were probably trade-in’s, but there aren’t that many of them. The only person that I know of, that actually acknowledged that he traded in an Apple 1, was Bob Bishop.

    Briefcase Apple 1 Sighting

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    There are a couple of original Apple 1’s that were put in briefcases.

    One is owned by the “Main Personal Comptuer Museum” and is depicted on my registry page.

    The one of interest for purposes of this blog entry is shown in an image shown on a webpage put up by the Silicium Museum organization. I don’t believe that the briefcase unit is the actual Apple 1 owned by the silicium organization. In fact, since I don’t have good documented images of their unit, I am just a bit skeptical about whether Silicium actually has an Apple 1. My standards for posting original Apple 1 information has risen since I added the Silicium unit, and if I recieved a similar report today, I might not have added their unit to the registry, at least until I recieved a good image.

    However, it is interesting that I just got another historic look at this same briefcase Apple 1. It was shown on the program Computer Chronicles, which has it’s shows archived at the site archive.org. It can be seen at the beginning of a show entitled“Apple II Forever”.

    I may have to add this unit to the registry, as a missing historic unit. There is a reference in the show to it being a museum piece. Since the show might have been taped in California, maybe it’s still sitting in some museum vault in the Bay Area.

    By the way, there is no better way to understand the history of personal computers than to read vintage publications and view vintage videos. The archive of “Computer Chronicles” show is priceless. Check out Bill Gates participating in the Computer Bowl II.