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• Minimal L-Star on a Breadboard, and KITS ARE BACK!

  Jac Goudsmit • 04/18/2020 at 08:42 • 0 comments

  I intended to get this done last weekend for the 44th birthday of the Apple 1 computer (April 11 1976) but unfortunately it wasn't meant to be. After I had put the circuit together, it didn't work at first. The 65C02 that I was using, had given the ghost, possibly because of me being careless with static electricity. I checked all the wiring first (which took a long time) and when everything checked out, I wrote a short program to slow the 6502 clock down to a crawl of 1 Hz or so, and write the INA input register to the screen on every clock cycle. That finally showed that the address bus and data bus were the same on every cycle, so the 65C02 wasn't running.

  After I replaced the 65C02 with another, everything worked just like it should, but by then it was Tuesday. Then I got some "distractions" from work and family life, and I could finally get back to it on Friday.

  I replaced the instructions section of the project here on Hackaday with instructions on how to breadboard your own L-Star for (probably) less than $50. Have fun!

  Oh, and by the way, I got parts for a batch of L-Star Plus kits. It will be back in stock some time this weekend. YAY!

• L-Star As a SuperCon2018 Badge Add-On

  Jac Goudsmit • 11/05/2018 at 19:27 • 4 comments

  Apple-1 emulator for SuperCon2018 Badge

  I turned my SuperConference 2018 Badge Add-on board into a 6502 computer, so if you're tired of playing Zork on a Z80, you can play Super Star Trek on an Apple 1 emulator.
  

  I didn't win the badge hacking competition, though I think I might have had a good chance to at least be admired on stage if I would have had 5 more minutes with a soldering iron; the add-on was basically working but it was disconnected from the badge because of a wiring mistake that I didn't notice until after all the soldering stations had disappeared.
  

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• PET-2001 Emulator Project Started

  Jac Goudsmit • 06/11/2018 at 20:02 • 2 comments

  If you've followed me long enough, you know that my original purpose for the #Propeddle: Software-Defined 6502 Computer project was to build a replica of the Commodore PET-2001 and CBM series computers. The PET-2001 was the first computer I ever used, when I was about 11 years old in 1978. And now I've finally made a start on writing a software-defined computer project to emulate the PET/CBM on L-Star. As you can see in the picture, I have a long way to go.

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• Back in Stock!

  Jac Goudsmit • 05/26/2017 at 06:38 • 3 comments

  Got parts, got PCB's, getting Prop Plugs in a day or two.

  That means L-Star is back in stock!

  Order here: https://www.tindie.com/products/jac_goudsmit/l-star-plus-software-defined-6502-computer/ (or click on the Tindie link on the project page).
  

• Some Ideas for the Future...

  Jac Goudsmit • 01/12/2017 at 23:05 • 4 comments

  I received the second batch of production boards and parts, so the kit is back in stock on Tindie. Meanwhile, I figured I should write down what the plans are, especially for the l-star.org website. See "after the break" for some ideas I'm working on.

  First of all, I've been working some tutorials for owners (or those who want to follow along at home) to learn how to "write their own computer" using the C language:
  

  • The first tutorial/demo proposes a basic framework that defines types and macros to get started, and generates a clock signal "as fast as possible" and lets you observe how the 65C02 reset sequence works
  • The second tutorial/demo shows how to run a separate cog that presents part of the Propeller's hub memory to the 65C02
  • The third tutorial/demo shows how the PIA of the Apple 1 can be emulated in C, and loads the ROM from Vince Briel's Replica 1 to make the L-Star into an Apple 1 emulator.

  The code for the above is already on Github here, but I'm still working on the text that will be posted on the website soon.

  Future Tutorials

  I'm thinking the next tutorials should be:

  • How to convert time-critical code into inline assembler, and how to use a Propeller timer as clock generator.
  • How to use the SRAM chip.
  • How to implement emulation of memory-mapped (text) video, and how to emulate a matrix keyboard, culminating into an emulator of the Ohio Scientific Challenger C1P (also known as the Superboard II or UK-101).
  • How to implement a virtual storage device using the EEPROM.
  • How to make up your own system, maybe running Forth.

  Future Hardware
  

  I have several ideas I want to work on in the hardware area:

  • Commodore PET emulator: this is what I originally intended the project to do, but it would need a way to generate interrupts at 60Hz or 50Hz and I'm trying to think of a way to do that without adding extra hardware.
  • Acorn Atom (a.k.a. Hob-bit computer) emulator; this should also be possible without extra hardware.
  • An expansion board with 24 (or more) tactile switches and six or eight 7-segment displays to emulate a Kim-1 or Elektor Junior
  • A "Pro" version for advanced experiments: this would probably be a version of the board that doesn't have the I/O and jumpers on board; it would have a right-angle connector for expansion, which would plug into a new passive motherboard (or simply an IDC connector on a ribbon cable) to connect to multiple expansion boards. Or, going slightly further, something resembling RC2014 but perhaps using card edge connectors.
  • A "Pro 16" version that uses a 65C816 instead of a 65C02 and has (say) 4MB of static RAM and runs faster while the CPU is not accessing the Propeller. This could perhaps be used to emulate the Mensch Computer or simply to run Fuzix. You know, just for giggles.
  • A modification to use a PIC microcontroller instead of a Prop Plug to connect it to a host system. This would eliminate the FTDI controller, the one and only chip in the design that's not available in a DIP package, and would make it easier to put the system into an enclosure.

  Are You Still Reading?

  I have disappointingly little time to get all this stuff done, and I hope owners and enthusiasts will step up to help some day. Whether you have a kit or not, if you've read through the documentation and you can think of something you want (me) to do with the L-Star, or if you would like to propose any ideas for expansion boards or software projects, let me know!

• Now For Sale on Tindie!

  Jac Goudsmit • 11/08/2016 at 05:34 • 0 comments

  I received the PCB's for the first production run!

  That means you can now actually buy the project as a kit on Tindie. Click the link on the project page to order.

  I'll be setting up the web site at l-star.org this week (hopefully), so that new owners will have a place to go to find build instructions, documentation, and maybe even a forum to share what they've done with the system, ask questions, or make suggestions. If it's going to be a lot of work, it means I'm doing it right!

  ===Jac
  
  

• Hardware Revision 5: Could This Be the One?

  Jac Goudsmit • 10/11/2016 at 04:15 • 0 comments

  After the disaster with Rev. 4 (see the last log), I learned a couple of things and made some changes resulting in Rev. 5:

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• So Much Fail: Building the Rev. 4 Boards.

  Jac Goudsmit • 09/13/2016 at 07:09 • 1 comment

  Last Friday, the Rev. 4 boards arrived from OSHPark, and a Purple PCB Day is always a good day. Also, BBC America was doing their Star Trek 50th Anniversary Marathon of all the Original Series episodes and I was the only one home, so this was going to be a fun night of watching the young version of Khan, Zefram Cochrane and the Tribbles, and soldering my project together. Or not?

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• Hardware Revision 4: Now with All the Pins You Need!

  Jac Goudsmit • 08/28/2016 at 22:08 • 0 comments

  This weekend I was able to do some work on the hardware of the project again, and I decided to bump the version number, so it is with pride and joy that I announce Revision 4 of the L-Star hardware.

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• Hardware Revision 3

  Jac Goudsmit • 06/15/2016 at 03:27 • 2 comments

  As I mentioned in the "Hardware Revision 2" posting, there were some small but significant problems with that version of the schematic and PCB:

  • The ~RAMEN pin ended up in the wrong place on the jumper block, which would make it difficult to use video, a keyboard and the on-board SRAM chip at the same time.
  • With the added on/off switch, the board got a little crowded around the RESET6502 button which made it harder to press the button. Also I didn't like that the buttons didn't line up nicely in the layout anymore.
  • The board still had the old problem that the solder islands for most parts/footprints were a bit on the small side.

  Here's a picture of the Revision 3 layout:

  First of all, I switched the location of A16 and ~RAMEN (and the accompanying 3.3V and GND pins) so that ~RAMEN can be jumpered to P27 which is connected to KBCLK in the "default" configuration. I considered moving things around so that ~RAMEN would be the default for P27 and KBCLK would be an alternative, but I decided it would cause too much confusion so I didn't do that.
  

  I moved the power LED to a location between the pushbutton switches, so now there should be enough space for a finger to push the button again. I also lined the pushbuttons up, close to the places where they were in revision 1. The LED is in a sort-of-odd place, so far away from the power connector and the power switch, but it's where there was enough space for the traces. I would have liked it on the right side of the board (and the power switch too) because I imagine that side will be pointing towards the user, but that's simply impossible unless I make the board a lot bigger.

  I edited all the footprints on the board and made sure that they all use solder islands with a size that's big enough to solder if you have a non-professional solder iron, or if (like me) you have some old solder tin that doesn't flow as well as it used to do.
  

  I discovered another oversight that I wanted to fix: the jumpers didn't have the ~RESET6502 signal on them. So I changed the jumper block from 7-by-5 to 8-by-5 and added the signal near the top, where it was easy to line up with the ~RES6502 pin on the expansion port connector. As it turns out, this had a fortunate side-effect: I found out that five 10-pin pin headers are cheaper than two 20-pin headers of the same series (the ones with the green plastic that I got by mistake but look really good and nicely define the color scheme of the project, along with the purple PCB and the red jumpers). This will make it easier to break/cut the jumpers to size for the final kit.

  I also made the footprint of the voltage regulators a little smaller, which allowed me to reduce the board size again, and to line up the power switch with the RESET6502 pushbutton.

  I haven't ordered parts or PCB's yet, because I'm considering another change: I'm thinking of putting the voltage regulators upright, and wiring them up differently so they'll be in parallel instead of in series. This will allow expansion boards to use more power on the 5V rail (the 3.3V regulator is currently fed by the 5V rail) and might reduce heat production because the current only has to go through one regulator instead of two. On the other hand, it might cause other problems like interference and the need for bigger electrolytic capacitors.

  Another change I'm considering is to use a 50-pin expansion header instead of a 40-pin one. You may have noticed that there is just enough space to do that, and that's not a coincidence. A 50-pin header would make it possible to run the video and keyboard connectors to the expansion board, as well as some signals (~BE, A16, ~RAMEN) that I had to leave out because of the 40-pin limit. This would make it possible to design an expansion board that e.g. generates color video and uses the PS/2 keyboard, without the need to add connectors for them to the expansion board. And it would be possible to let an expansion board take over some functions take over some functions that currently only...

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