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Whatever you've got there, it is totally custom-built, certainly not an official Lego product.

It looks like something custom for the 9V system.

Not to rain on your parade, but if your goal was a complete Lego robotics timeline then why don't you have any of the pre-Mindstorms stuff?

This thread is for discussion about hacking the Lego set 9750, also known as "Interface A", primarily using 8-bit systems from the 1980s. Forum members such as @Toastie, @alexGS, and I have long been hijacking other threads so it's time to make a new one. Administrator @Jim may move some of the recent posts over here. From around the middle of the 1980s through the early 1990s, Lego endorsed (via published applications and teacher's manuals) seven programming languages with Interface A: 6502 assembly, BASIC, COMAL-80, Lego Lines, LOGO II, LogoWriter Robotics, and TC LOGO. (As I'm typing this, I just realized that I can't count: I wrote "six" on my website at http://www.brickhacks.com/6.php. It is indeed seven choices! I'll fix it tonight or tomorrow.) Lego also endorsed five kinds of computers: Apple II, BBC Micro, Commodore 64, IBM PC, Philips P-2000 (and all of the relevant sub-models, clones, etc. -- for example it's perfectly acceptable to use a Laser 128, Commodore 128, generic PC, etc.) The challenge How may the system have been hacked, using only technology that was commonly available from 1987-1992? Rules: 1. Use any computer and any programming language you like, as long as it was for sale in 1992 or earlier (as the next-generation 9751 / Interface B debuted in 1993.) 2. Don't use any add-on hardware that was not available back then. A breadboard is fine; an Arduino is unacceptable. 3. It's okay to run emulators if you do not have original machines, but you can't use any additional features that did not exist back then. You can use Windows 1.0 or 2.0, but not 3.1 libraries, etc. I'll be the judge, jury, and executioner and with permission I'll feature the best answers on my website. Everything from this point on, ending after Jim's post 7 hours ago, is content that he moved from the other thread. ------------------------------------------------------------------------ Everyone -- @alexGS documented his method, at my request, of using a PC parallel port so you don't need the ISA card. His work is based on Tom Cook's earlier work. I linked to his document at http://www.brickhacks.com/4.php Personally I prefer using the original hardware :) and still have a few of the PC kits with ISA cards for sale. I invested a substantial amount of money in these, so I'm hoping people here want to buy them!

YES!!!!!

Excellent!!!

@Phoxtane - The best way to test the 4.5V accessories is to plug them into Lego set #9750, "Interface A" (I have some extras if you'd like to buy one -- send me a private message if you're interested.) Interface A has six outputs (lights/motors) and two inputs (optical and touch sensors). The output ports are approximately 3.5 volts and the sensor ports are approximately zero-point-3 volts.

This is the one I have: https://www.amazon.com/Hakko-FR-301-Desoldering-Tool/dp/B07BKSLLG9/

Last winter, I asked Hanukah Harry / Solstice Sam ... aka my wife ... for a vacuum desoldering station. They obliged! It's a pleasure to use vs. wicks or hand-powered solder suckers. Let the tip heat up, apply to your solder joint, squeeze the trigger. WOMP! The solder magically disappears. I love it.

Don't apologize, you're probably right. I just figured in * this * sub-forum no pictures or further explanations are necessary. :)

Guys - I've got a dilemma. A few months ago, I found someone selling a massive supply of our favorite Lego gear. So now I'm in possession of too many 9750s, too many 9771s, and too many 9700 kits. I sold a couple of them already, but I need to sell the rest soon, because of credit card bills. I want these go to people who'll really appreciate them -- I don't want to see people hoard them, or stick them on a shelf and never use them. And I'm not trying to make a profit, I'm only looking to recoup my costs. I'm offering five bundles for sale. Each bundle includes two 9700, one 9771, and one 9750. The cost is $400 each (US), plus shipping. I previously posted in the for-sale forum but we all know that here in the 9750 discussion is where people might actually respond. :) I also expect to have some extra 9700 kits, maybe a few extra 9750s, and some other miscellaneous stuff, after the bundles are sold. Please help me out by buying these bundles :) because I got myself into too much debt, so I'm panicking a little bit. Last year I purchased a bunch of the Apple II versions, and those found new homes very easily. I expected the same from the PC versions. It's not been the case. I also have avoided putting these on eBay or Bricklink. Rather get them to the best hobbyists and people I know!

800/800XL are both valid, in my opinion. I don't have a specific trash-80 in mind. I guess just one of the consumer systems, not one of the business systems. Altair would be a stretch, or maybe it would be easier, who knows ... the people I know who are into S-100 can make them do cool things that I don't always understand. I used to have access to all of these and a lot more, when I was in charge of a computer museum here in NJ. I left that organization in 2019. I'm still friends with some of the members, but I no longer have easy access.

I'm wondering about other systems such as the KIM and Ohio Scientific series (both 6502), TRS-80, and even an Altair.

I want to see somebody make it work on an 800, or a TRS-80.

Except that the video title says 90s! It should be 80s.

Congratulations, @Toastie, you win. :) Your prize is bragging rights! I updated my page at https://www.brickhacks.com/2.php.

@Toastie this sounds good to me! I have an idea for a (shhhh!) secret project ... I'll send you a private message.

I haven't tried yet.

Yes! When I commented a few weeks ago, I hadn't read the earlier comments. But you are absolutely right. @Coder Shah it is imperative that any Mindstorms history recognizes how Interface A was NOT invented at MIT or by Lego, but from the English organizations mentioned on my website. It's a coincidence that MIT was separately working on their own Lego robotic designs around that time. This is all preceded by Lego's own analog robotic system from the 1980 Idea Book, #8888.

I see your point about a nice-looking test pattern. I just figured it would be 63 (all on) or, as you noted, 42 - now THAT would be appropriate! Lego engineers clearly had a sense of humor. To check the connection of the 9751, your code must send a text string to Interface B: "Do you byte, when I knock?" and confirm the interface's reply, "Just a bit, off the block." The weird part is, the text string is mentioned in one of the 9750 manuals! (I forget which one right now. Just got out of bed. I'll check later.)

Here's something weird. In the Lego-provided IBM (9771) code (http://www.brickhacks.com/ibmbasic.php), the check-out lines are: 10000 P=925 10010 OUT P,21 10020 IF (INP(P) AND 63)=21 THEN OUT P,0 ELSE ERC=4 : GOTO 20000 In 10010, I have to wonder: why is the test value 21? What's special about that number?

Here are the BASIC and COMAL-80 instructions that came with the Lego Commodore 64 cable ... again in German! https://archive.org/details/lego_c64_manual_basic_comal

I re-uploaded the book to the correct collection ("Vintage Lego Robotics"): https://archive.org/details/steuern-und-regeln. Now I'm going to scan the COMAL-80 instructions, which came with the Lego C-64 cable.

Do you still have the picture? What was the source?

I emailed the author again to ask about the disk. I didn't know there was an accompanying disk until Toastie mentioned it today.