Gregory's Serverin July i bought an old Fluke benchtop multimeter. while repairing it, i discovered a bad custom chip. i made a PCB replacement for it! https://mastodon.social/@tubetime/110646271352858078
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 while working on the RS/6000, i discovered that it required a special PS/2 keyboard that implemented an extra command. i made a little box that lets you use a standard PS/2 keyboard. https://mastodon.social/@tubetime/110798263588229059 with all these workstations on my bench, i designed a video adapter to convert 13W3 connections to standard VGA. https://mastodon.social/@tubetime/110726122938943639 remember that Thinkpad 700 from earlier? i started a massive project to build a replacement solid state hard drive for it. the drives were not IDE; they were a special IBM interface called DBA-ESDI. https://mastodon.social/@tubetime/110783604330499249 did you know that some early radio transmitters were electromechanical? i didn’t either! https://mastodon.social/@tubetime/110970146022678448 at the last Electronics Flea Market (in September) i found a strange bit of electromechanical aircraft avionics. check it out! https://mastodon.social/@tubetime/111043677193721723 some old DOS utilities had a graphical mouse cursor in text mode! i’ve investigated how they did it. https://mastodon.social/@tubetime/111123817309591559 in October, i spent a bunch of time reverse engineering the power board from the IBM Thinkpad 700. it was a good excuse to switch to KiCAD 7, which allows you to overlay your layout on top of an image–perfect for reverse engineering work! https://mastodon.social/@tubetime/111298635503517686 most recently, i reverse engineered a rare Apple II sound card (a sampler) using some blurry photos AND ARTWORK ON A RECORD ALBUM COVER!! https://mastodon.social/@tubetime/111508413193886509  @tubetime It was done dynamically redefining the appearance of a group of characters. This was only possible on VGA (and some older EGA) video cards. Assuming the mouse pointer can move one pixel in any direction, and the mouse pointer occupies the room of only one character, you will need to redefine one, two, or four characters, depending on the pointer location.  @tubetime Oh, that was not that difficult. VGA could display two 256 char fonts at once. You selected thag by a single bit in the color attribute. All you need to do is to render the characters occupied by the mouse-cursor into font2 and put the mouse-cursor image on top of it. Then adjust character and attributes as needed. You could render quite a bit of bitmap graphics that way in text-mode.  @tubetime that was the next step after spark gap transmitters, IIRC.   @tubetime one of my backburner projects is a simple Arduino-based USB to PS/2 adapter, initially to do some fun stuff with older PS/2 mice - do you have any good references or other examples for PS/2 comms that you could share? I had a look at the code for this and have a pretty good idea of what's happening (great comments!) but implementing something myself still feels a bit daunting. @timixretroplays can't help you with the usb but you could look at the ps/2 code in my adapter: https://github.com/schlae/RS6KB/blob/main/RS6KB.ino |
ever shelve a project for a long time and revisit it later? i built this Panaplex clock 4 years ago but didn’t finish it up and release the design until July. https://mastodon.social/@tubetime/110680469380657195