Musings about Kevin's world
This is a continuation of fault finding and (hopefully) fixing my ZX Spectrums. Since working through the pre-power up checks in ZX Spectrums – Part 2 I ve acquired another rubber key an Issue 3B, so I ve added the pre-power up checks of that to my table too. This post looks a bit more at the Continue reading ZX Spectrums Part 4
As part of my tinkering with the RC2014 I wanted an easy way to transfer ZX Spectrum compatible assembly over to an RC2014. Naturally the language and code itself are pretty straight forward, but when it comes to what the assembly code is attempting to achieve this will be quite different. There are a number Continue reading ZX Spectrum Compatible Video for RC2014
Having spent far too long chewing over how the Raspberry Pi Pico Scanvideo library works over in Simplified Pico VGA, this post actually starts to do something with it. One constraint I have for myself, is that I want to keep using the Arduino IDE for the Pico, so the first step is to see Continue reading Simplified Pico VGA Part 2
The Raspberry Pi Pico Hardware Design Manual has an example board that shows how an RP2040 can be used to create a VGA signal using a 3-way 5-bit resistor DAC. It is the basis of the Pimoroni Pico VGA Demo Base which makes messing around with it pretty easy. But the downside is that it Continue reading Simplified Pico VGA
After the final successes of the past post, I thought it would be worth formally building a diagnostic module that can be used to help debug the system should the need arise. Diagnostic Module Design This is a reimplementation of the breadboard diagnostic breakout used in Part 6: But I m building it all onto a PCB Continue reading PDS – the Programmers Development System – Part 7
One of the issues I had with my ZX Spectrums at the time I started writing this was no working keyboards! I ve now replaced some membranes (see ZX Spectrums – Part 3) and have two working machines again. But I have others to look at and as I also have an unbuilt Harlequin for a rainy Continue reading ZX Mechtrum
This series of posts looks at the Programmers Development System (PDS). This part gets serious about attempting to debug eveything and find out why it isn t working PDS Diagnostic Breakout The starting point is trying to figure out what is going on with the signals on the link. To do that, I ve built a simple Continue reading PDS the Programmers Development System Part 6
In this part I m finally getting to properly test the boards, having finally managed to acquire all the parts I need: namely a working ZX Spectrum, an ISA based PC and the means to get software onto them both. In terms of documentation for using the PDS, I have found the following: The first describes Continue reading PDS – the Programmers Development System – Part 5
In this post I m actually starting to get some of the machines back up and running properly, starting with those two Issue 2 boards. Keyboards Following on from ZX Spectrums – Part 2 the Issue 2 in the Plus keyboard seems to require the least amount of work essentially just requiring a new keyboard membrane Continue reading ZX Spectrums – Part 3
Following on from my previous posts (Part 1 and Part 2) rather than a nest of jumper wires, I ve put together a RP2350 PGA RC2014 breakout based on the PGA2350 Breakout PCB. PCB Design This is using the same mapping of Z80 bus signals to RP2350 GPIO pins as used previously but of course this time Continue reading Watching a Z80 Bus from an RP2350 – Part 3