Blog · corpus.blog/blogs/michaeldoornbos.com/posts
michaeldoornbos.com
michaeldoornbos.com
2022
There’s an add on to the romulator that uses an ESP32 to get rid of the need for a Raspberry Pi to flash it. But it does result in a strange tower of instability. I think I’m gonna just add a JTAG cable between them and lay it in the case out of the way. #commodoreoriginal ↗
17 Jun 2022
Getting back to the 6560/1 drop in replacement project. Ended up just using a foam board to lightly double side tape everything on. This allows me to move the whole thing when I need the desk space for something else. Need to connect all the wires now #vicsrevenge #commodoreoriginal ↗
17 Jun 2022
Put @adumont’s custom bios and 6502 Forth implementation on my CERBERUS 2080. I guess I’ll have to actually learn Forth now :) Happy Friday!original ↗
17 Jun 2022
Happened to open Hacker News this morning and noticed someone submitted my article and I’m number 3 this morning. Since this internet is only for complaining these days, I think I will NOT read the comments.original ↗
16 Jun 2022
Had this DIP-40 to IDC socket cable custom made and it looks fantastic. At least one part of the project will be neat and tidy #commodore #vicsrevengeoriginal ↗
15 Jun 2022
Broke out the Cerberus 2080 this morning to test out an idea on a 6502 at a fast clock speed. 8Mhz should do.original ↗
14 Jun 2022
Ended up springing for the most up to date version of this book because… RISC-V. Lots and lots to study in here. #fpga #riscvoriginal ↗
13 Jun 2022
This is just the summer book pile that’s on my nightstand. There’s another this high on my office desk. Good thing I’m a fast reader :)original ↗
11 Jun 2022
Atari VCS/2600 composite video mod is pretty straightforward. What better game to smoke test with than Yars’ Revenge :) #atarioriginal ↗
10 Jun 2022
Before work this morning I got an okayish mod to the “worlds worst paper tape reader” working. Now can somewhat reliably read the sprocket holes and use them as a timing signal. Super happy at this point and I may call this “complete”. #kim1 #commodoreoriginal ↗
10 Jun 2022
Guy up the road from me called and said he found this unopened laptop in storage and do I want it? I literally just pulled the plastic off of an Everex 386. The screen contrast/over brightness needs work and the hard drive is toast. 40 pin DIP EEPROM is kinda neat.original ↗
9 Jun 2022
I was feeling like living dangerously today so I broke out Schrodinger’s cat of computers. The cat is alive today ;-) #commodore #plus4original ↗
9 Jun 2022
Broke out the PC-4 to use for my day job today. Post by @HeyBirt reminded me how great it is :)original ↗
9 Jun 2022
Okay, so I got off on a bunny-trail working out how to get Jim Butterfield's Lunar Lander for the KIM-1 printed on paper tape. Back off man, I'm a scientist! #commodore #kim1original ↗
7 Jun 2022
Waiting on some parts for the VIC chip replacement project so that’s on hold now this week. Might build this Super Snapshot replica board this evening. #commodoreoriginal ↗
6 Jun 2022
I know you were just sitting there wondering if a VIC-20 will boot off of an external 3.3v clock signal. The answer is surprisingly: yes. Scope here shows activity on all of the RAM from the CPU. Neato! #commodoreoriginal ↗
6 Jun 2022
This VIC-20 got HOT. Swapped the linear regulator with a modern switching ($9). Before: 46C drawing 2.3 amps. After: 26C drawing 1.03 amps. Much better. #commodoreoriginal ↗
6 Jun 2022
I’m gonna need to set up a dedicated workspace for this #vicsrevenge project. My desk can’t look like this for a year. Hmm. #commodoreoriginal ↗
5 Jun 2022
I'm collecting Verilog examples and tutorials. If you have recommendations, please let me know. Bonus if they are in book form. #FPGA #Verilogoriginal ↗
4 Jun 2022
Happy friday! How about a little 80 column PET love this morning? Zig Zag array will do nicely. #commodore #PEToriginal ↗
3 Jun 2022
With bi directional level shifters the final board will have less chips. VIC-20 system clock replacement from the FPGA. 3v logic input is yellow, 5v output is purple. Freq is correct. Shape needs work. Ringing is mostly breadboard parasitics #commodore #vicsrevengeoriginal ↗
2 Jun 2022
Romulator by @bitfixer is turning out to be a great troubleshooting tool for repairing VIC-20s. This is the second board donated to the #vicsrevenge 6560/1 drop in replacement project I was able to get working again in a few minutes with the Romulator's help #commodoreoriginal ↗
1 Jun 2022
I'm sure there are libraries for this, but creating the MOS parts in KiCAD is helping me wrap my mind around everything. 6560/1 is this morning's project, I'll open source (Github) when I have them all done and correct #commodore #vicsrevengeoriginal ↗
1 Jun 2022
At least this transformer is in a case with screws. Might be nothing more than this fuse being blown. #commodoreoriginal ↗
29 May 2022
This first VIC-20 I received to repair just ate a transformer. What the hell is this? Looks like a solder blob dead short to me right? Good one is second same part. #commodoreoriginal ↗
28 May 2022
Pro tip: riding lawn mower engines don’t start if your fuel cutoff solenoid goes bad. I didn’t want to cut the grass today anyway :)original ↗
28 May 2022
Taking a couple day break from the VIC project until some 74LVC245s arrive. In the meantime, I think I’ll take a little detour.original ↗
28 May 2022
27 May 2022
I love the VIC-20, but sometimes formatting stuff on the screen can be challenging. Happy Friday! #commodoreoriginal ↗
27 May 2022
Ever flip over to another virtual desktop and have to ask yourself more than once “wait, why was I working on this?”. Yeah. Thursday.original ↗
26 May 2022
Wrote some scripts to create 32 and 64k ROMs so I can test sending addresses and reading the data bus without worrying about RAM timing with the CPU for now. Split the problem and tackle one half at a time right? Put a 'frozen' screen at A000 for now. #vicsrevenge #commodoreoriginal ↗
26 May 2022
My new favorite browser plugin. Your brain, like your body, is what you feed it. Don't let others (or algorithms) feed it for you.original ↗
25 May 2022
I was just looking at my logbook and need a couple approaches for IFR currency. Do you think the FAA will accept this VIC-20 Simulator? It works surprisingly well. I'm just saying FAA, could be good enough. #commodoreoriginal ↗
24 May 2022
One of my 2022 goals is to finish both of these including typing and understanding (as best I can)every example on both the C64 and VIC-20. Just finished the BASIC book, so slightly ahead of schedule. On to the Kernal book. I blame @8BitShowAndTell for this one :) #commodoreoriginal ↗
24 May 2022
I know you were just sitting there thinking "What IS the clock divider setup to run a VIC-20 without needing the onboard clock circuit working? 1.10822Mhz is pretty specific." Well today is your lucky day. #vicsrevenge #commodoreoriginal ↗
23 May 2022
Just thinking it would be nice to be able to read VIC-20 video RAM in real time. Then I remembered I have a Romulator (for a year, never used). Unfortunately the vram isn't implemented yet, but I can still dump the rest of memory to a file which is nice. #commodore #vicsrevengeoriginal ↗
22 May 2022
Picked up a DM-42. I blame @svenpetersen191 for this one. I resisted the purchase as long as I could. Amazing how it’s almost exactly the same size as my very well worn HP-42original ↗
21 May 2022
I don’t think I can get away with NOT level shifting from 3.3 to 5v on a VIC-20. Probably not… But there sure are nice and cheap tools for things these days. Need a completely configurable 3 output 8khz to 160Mhz clock generator? That’ll be 6 whole dollars please.original ↗
20 May 2022
Beautiful VIC-20 board donated by the amazing @cmherndon79 for the 6560/1 project. This board will be the one that gets the prototype board for testing. #commodore #vicsrevengeoriginal ↗
20 May 2022
Well that.. DEFINITELY looks like a Composite video signal (PAL). Woot! Now on to the interlace math and the NTSC version. Urg, do we REALLY need interlacing? VGA is SO much easier... #commodore #vicsrevengeoriginal ↗
20 May 2022
Why spend 10 seconds sketching a timing diagram for VIC-20 video output signals when you can spend 20 minutes doing it on an actual VIC-20? Happy almost Friday ;) #commodore #vicsrevengeoriginal ↗
19 May 2022
Didn’t get a chance to post this earlier (work), but the next step in the VIC 6560/1 project is to create composite out on pins 2 and 3. This is at least starting to look something like a composite luma signal, kinda. One step at a time. Back to day job! #commodore #vicsrevengeoriginal ↗
19 May 2022
First time I've used this modeling software and was impressed. Working out NTSC Luminance timing logic is a big help after just a couple mins. 100Mhz clock on the FPGA so we can just count nanoseconds. Can export to Verilog after simulation. Most excellent #commodore #vicsrevengeoriginal ↗
18 May 2022
18 May 2022
Progress this morning before the day job kicks in: I have an externally clocked VIC-20! Internal timing being driven my an ICE40 FPGA. It’s a couple cycles slow but getting there. Now to start on video signals. The math makes my brain hurt. More coffee #commodore #vicsrevengeoriginal ↗
18 May 2022
One of the very strange quirks about NTSC and PAL Composite video on VIC-20s is the half frame interlacing and the offset odd numbers you have to "count". So how long exactly is each frame SUPPOSED to be… #commodore #vicsrevengeoriginal ↗
17 May 2022
Next step in the #vicsrevenge project is to create the two out of phase clocks that the CPU uses. This 6561 outputs pretty close to the spec. #commodoreoriginal ↗
17 May 2022
I do buy legit copies of JiffyDOS from Jim B and even buy the official switcher when I need them. Sure I can burn my own with pirated copies, but a legit license is $8 whole dollars. Cmon man. #commodoreoriginal ↗
16 May 2022
In case you're one of THOSE people who was just sitting there thinking "what ARE the startup values in the VIC chip registers on a VIC-20?" Well, you're in luck. #commodoreoriginal ↗
16 May 2022
Gonna have to build some sort of test bench jig if I’m going to have 32 leads connected to the VIC chip at once without it being a wire hot mess. Good news it the DreamSourceLab 32 channel analyzer arrived and took about 60 seconds to set up. #commodoreoriginal ↗
16 May 2022
Well this is good, turns out I do know how to create a B&W PAL (and NTSC) Composite/S-Video signal from scratch. My timings aren't quite right, but it's close. Good first crack though. #commodore #VIC20hacking #learnallthethingsoriginal ↗
15 May 2022
14 May 2022
Actually read the manual for my scope yesterday. Turns out it’s crazy easy to trigger on a PAL horizontal scan line number. On 110 here you can clearly see the blinking cursor. Turns out RTFM is a good idea after all. #commodoreoriginal ↗
14 May 2022
14 May 2022
13 May 2022
12 May 2022
I think I've decided on a working codename. Logic analyzer ordered and shipped. I'm shooting for a working version in a year.original ↗
11 May 2022
8 Bit processors can count to 18 Quintillion just fine. "Wheat and chessboard problem" in 6502/10 Assembly for my "learn something every day" task. #commodoreoriginal ↗
9 May 2022
I tell myself I have some lofty career aspirations to justify my deep dive into learning to code FPGAs this year. But I know deep down it’s so I can try making drop in replacements for things like this, which I found in my stash. It tests good in my only NTSC VIC 20 #commodoreoriginal ↗
7 May 2022
Think I found the color film I’m adding to all of my 7 segment displays to help them show up better on phone camerasoriginal ↗
6 May 2022
I own a couple dozen calculators. I checked and only two of them can multiply two 32-bit numbers and give me the full 64-bit product. The@NumWorks and TI Inspire. Oh, and a Commodore 64 if you can code in Assembly;-) #commodoreoriginal ↗
6 May 2022
I own a couple dozen calculators. I checked and only two of them can multiply two 32-bit numbers and give me the full 64-bit product. The@NumWorks and TI Inspire. Oh, and a Commodore 64 if you can code in Assembly;-) #commodoreoriginal ↗
6 May 2022
5 May 2022
Finally got around to doing the S-Video Mod on my Vicky-20. The results are pretty good. Probably about as good as you can get from a VIC-20 of any kind, so certainly nothing to complain about there. #commodoreoriginal ↗
5 May 2022
Had some fun last night playing with SYS parameters and learning a lot. Here's extending BASIC to implement a PRINT AT equivalent on Commodore 64/VIC-20 to do the 100 Door problem. Again ;-)original ↗
4 May 2022
Writing an article and occurred to me I need to add a word to my Mac dictionary... #commodoreoriginal ↗
4 May 2022
Picked up a set of gymnastics rings to add to my workout setup at home. I do enjoy these “users instruction enjoyment and importance” lost in translation comic books they included. These tapes are kindly prepared…original ↗
3 May 2022
Next to the Corsham KIM-1 the KIM Uno looks crazy tiny (it is). I heard from questionable sources that it’s more about how you use it than the size so don’t worry little KIM Uno, it’ll all work out. #commodoreoriginal ↗
2 May 2022
I built a paper tape reader from scratch without any reference designs. Someone pointed out there there’s a book from 1979 that has designs for this in it. Annndd I happen to own this book…. Sigh. Let’s tell people I wanted to do it the hard way on purpose shall we?original ↗
2 May 2022
Alright, going outside for the rest of the day but I promised myself I'd go from novice to expert(ish) in @JuliaLanguage in 2022 so I needed a project I want to work on. Implementing a 6502 emulator seemed pretty natural to get started ;-)original ↗
30 Apr 2022
Success! The world's worst paper tape reader: Decoding on the PAL-1(KIM-1 Clone), LEDs (because blinkenlights) AND VIC-20 at the same time!original ↗
29 Apr 2022
Success! The world's worst paper tape reader: Decoding on the PAL-1(KIM-1 Clone), LEDs (because blinkenlights) AND VIC-20 at the same time! Timing is tricky by hand, but I couldn't be happier with this complete hack job that actually works. Are YOU keeping up with the #commodore?original ↗
28 Apr 2022
Worlds worst paper tape reader mid week progress: Test creating the enclosure peices. Not thrilled with the PVC as a material. Might move to ABS or maybe even a hardwood, but this cheaply confirms my design looks good. Happy camper.original ↗
27 Apr 2022
Worlds worst paper tape reader progress: this is just as good as drawing schematics right?original ↗
26 Apr 2022
Made some changes to the Turbo Macro Pro / Super Snapshot Cheat sheet based on input from @K0FFY_Radio #commodoreoriginal ↗
26 Apr 2022
Submitted some changes to the Commodore BASIC version of the Identity Matrix on @rosettacode so it displays better. The original was a copy of the AppleSoft BASIC and had way too much whitespace. If it looks good on a VIC-20, it'll look good on the other #Commodore machines ;-)original ↗
26 Apr 2022
Took a break from @JuliaLanguage for a bit but I’m gonna try it for an ML project I’m starting. Sure is zippyoriginal ↗
25 Apr 2022
Picked two of these up from @CommodoreKazz for use in hooking up a VIC-20 and a 128 to the worlds worst paper tape reader #commodoreoriginal ↗
25 Apr 2022
Worlds worst paper tape reader needs some custom parts so I pulled the X-Carve out of storage. Got it cleaned and calibrated. Figured making a sign was a good verification test as letters require then precision I’ll need.original ↗
24 Apr 2022
I generally wear my mistakes as a badge of honor. But I made a mistake on the vertical stab that's gonna require me to probably have to rebuild it. Very expensive mistake. Sigh.original ↗
23 Apr 2022
I LOVE Mr Hildon's Inner Space Anthology. But every once in a while I get to a part that is... kinda wrong ;-) #commodoreoriginal ↗
22 Apr 2022
Been a fan of Dave’s YouTube channel a long time and finally picked up his book. Really looking forward to this one.original ↗
21 Apr 2022
Couple conference calls in a row this afternoon. I pay attention better if I’m doing stuff with my hands so I started building another Eater 6502 breadboard computer. Everyone has two these days right?original ↗
21 Apr 2022
When I was a kid, the USR ports on my #Commodore machines were a mystery. Now, they are crazy useful and easy to understand. Always learning...original ↗
20 Apr 2022
Worlds worst paper tape reader mid week update: I can get a pretty solid 1.4 volt square wave with cheap copy paper. Thicker paper will be closer to 2.4. Both are clear enough waves to be fully usable. Time to fire up the CNC machine to make the mounting brackets. Awesome!original ↗
20 Apr 2022