🇩🇪 Nixdorf LK-3000 Personal Computer: Part 5 (Arduino Cartridge) [#TCE0650]

Thanks to #PCBWay for their ongoing support! https://www.pcbway.com I think my Arduino "Hello World" sketch is working properly on my "development system" ... it can output to the display, scan the keyboard, debounce the keys and also handle the shifted key functions (holding the [f] key down). I also developed an Arduino based cartridge that "mostly" works - the LK-3000s I have seem to have various problems due to the leaky NiCd cells inside them. I plan to make some improvements to the cartridge design anyway: add an ISP header and a buzzer. All the details are on my Github for this machine which will be updated as I progress: https://github.com/BrettHallen/Nixdor... 00:00 ... Intro 01:15 ... Arduino sketch demo 02:25 ... Arduino cartridge 04:12 ... Arduino cartridge built 05:40 ... Testing 08:15 ... Disassembling the test LK-3000 10:25 ... Trying other LK-3000 units 16:40 ... Plan to dump ROMs 17:05 ... Channel thanks & outro -------------------------------- From Part 3: We'll use an Arduino Uno due to its simplicity and its size ... it should be small enough to implement a barebones Arduino on a self-contained cartridge. There's two aspects we need to take care of: reading the keyboard and writing characters to the display. As they are "smart" display modules we don't need to refresh them at all once the data has been written. Nice. The biggest hurdle to my understanding was how the 7-bit ASCII (0x20 to 0x5F) codes were loaded into the displays via the cartridge interface which only has a 6-bit data bus. It turns out that in the 0x20 to 0x5F range the value of D5 and D6 are ALWAYS opposite ... so if we set D5 then D6 is also known, and this behaviour is handled by the CD4503 buffer chip. How very clever. We have four address bits available ... two to address the four characters in each module and two to address the modules themselves, 16 characters in total. Each character can be addressed individually. For now we will just concentrate on getting the display working. When my development keyboard arrives we'll look at the keyboard scanning side of things. -------------------------------- From Part 2: Let's see if we can put this machine to some use in 2025. I was initially just going to re-use the HPDL-1414 display modules but then thought it might be more interesting to use the whole machine as is ... it supplies a keyboard & display ... we just need to supply the CPU and firmware! As the machine is quite simple I drew up a schematic on how I think it works, including the keyboard matrix ... we either check the data bus for a key being pressed (keyboard strobe), or we put an ASCII character onto the bus and get it displayed (display strobe). So simple that I almost understand it. I designed some simple cartridge PCBs for initial development & testing - one cartridge with a prototyping area and one with a breakout header to allow development externally (i.e. wired up to an Arduino). I captured some signalling on the cartridge interface (Saleae Logic 2) to get an idea how we should talk to it ... whilst the development cartridges are being fabricated, I can whip up some Arduino code to check the keyboard and print to the display. Some discussion of possible uses here: https://forum.vcfed.org/index.php?thr... -------------------------------- From Part 1: Let's take a look at this interesting "personal computer" from 1979. It's essentially a language translator using cartridges but has a few other tricks: it can be used as a calculator, an electronic notepad, a filing system and also a remote computer terminal (via an acoustic coupler). The machine has a very nice 16 character display (four DL1414 modules) and runs on four NiCd rechargeable cells. It also comes with a 6VDC power adaptor that can be switched between 120VAC and 220VAC. There is very little inside the machine itself - a few logic chips, the display and the battery. All of the intelligence is contained within the cartridges: usually a ROM and a CPU-type device. -------------------------------- Check out my Patreon for regular blog-type updates between videos - there is a free membership tier and two paid tiers (US$2 and US$5). There is also a one-week trial for the paid tiers so if you don't think it's worth it, then cancel ... no hard feelings ... I appreciate any support, even if it's just subscribing to my YouTube channel!   / thecluelessengineer   -------------------------------- Music by Karl Casey @ White Bat Audio https://karlcasey.bandcamp.com    / @whitebataudio