Category Archives: 68K

Sound and video; more MAXI000 bring-up

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The build of the MAXI000 board continues. The first job was to finish the quad UART construction. The RJ45 and RJ10 sockets and the MAX238 (PDF) with its associated tantalum capacitors were all attached without any difficulty. After fixing a dodgy joint, caused by there being not enough paste on a corner pin on the MAX238: success. The bootloader was… Read more »

MAXI000 bring-up progress

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The build of the MAXI000 board is proceeding fairly normally. There have been a few issues along the way, all caused by either bridges or open pins on PLCC parts. As predicted these packages are a pain to rework with the iron; fixing them up after reflowing paste has been somewhat tricky. The biggest headache is not fixing bridges but… Read more »

MAXI000 initial bring-up and some workbench improvements

The bring-up of MAXI000 is still in the very early stages, despite the relatively large amount of bench-time that’s gone by since the boards and other parts arrived. I ended up using jlcpcb.com in the end, as they were a fair amount cheaper then allpcb.com. The bare boards look great: And the back: The reasons for the slowness in getting… Read more »

A PS/2 interface and PCB routing progress

Routing the MAXI000 board has been a slog. A mostly enjoyable slog, but a slog all the same. Before actually getting to the PCB design, the first task was to associate footprints with each schematic symbol. I always dread this task; you are presented with an intimidating list of symbols from the schematic and must pick the correct footprint for… Read more »

More prototyping and a description of the MAXI000 schematic

In the post which first discussed the MAXI000 board I plan to build, the idea of using a programmable oscillator to generate the pixel clock for video output was brought up. A programmable pixel clock would have a big advantage: video modes would not be fixed by the choice of pixel clock oscillator. It would be possible to experiment with… Read more »

Keyboard finished and PCM sound output prototyping

The bring-up of the keyboard controller board was a protracted affair. The first problem was obtaining an RJ10 cable. When drawing up the schematics for the IO board and the keyboard controller board I had naively assumed that the RJ10 cable I had salvaged from an old telephone was wired straight through with pin 1 connected to pin 1 etc…. Read more »

Keyboard controller construction and a DRAM controller

Receiving deliveries of brand new electronic components is exciting! The order from Mouser included a part for the keyboard controller board and multiple parts for MAXI000. On the same day I also received the previously described PCBs from allpcb.com. Here’s the front of a keyboard controller board: As usual they look great. A quick test of the updated RJ10 socket… Read more »

A mini-review of a microscope, a keyboard controller, and a SIMM adapter

When building PCBs with small Surface Mount components, it helps to be able to view the board with some magnification. This is useful for both the actual placing and soldering of components, and for inspection of the board after the fact. With the practice boards I made up previously I did have a look at them, after the soldering, with… Read more »

Thoughts on the MAXI000 and other things

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Before getting to the MAXI000, a brief discussion on some unrelated things. First up, I’ve finally bought an oscilloscope, specifically a RigolĀ  DS1054Z. This is a fairly low end 50Mhz DSO (Digital Storage Oscilloscope), which should nonetheless be perfectly adequate for my needs for the foreseeable future. One nice feature: it has four inputs. I must admit that a lot… Read more »

IO board bring up

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The IO boards arrived about a week after putting the order in. The front of one of the boards: And the back: Interestingly I received two extra boards. An extra usable board and another one. The other board had been used for some kind of testing by the manufacturer as it had a piece cut out of it. The box… Read more »