Technical preservation of Vintage Computers

March 31, 2021

I love my retro computers and the Internet does too, given the massive number of web sites out there dedicated to them.

A recent great find of mine is James Lewis’s Bit Preserve site on github. Unlike most retro sites which try to preserve an old computers operation manuals, service manuals and programs verbatim, Jame’s site goes further and is trying to preserve their technical designs by “recreating classic computer schematics. Let’s convert all those random scanned PDFs into a modern, editable and re-usable format”, to quote him directly. James gives an excellent video introduction to the preservation project.

The preservation project has picked KiCad as the primary schematic capture tool.

Whilst many of the directories are empty, the current system wish list is:



    Apple II
    Apple II+
    Apple IIe
    Apple IIc
    Apple III

    VIC 20

    ZX 80
    ZX 81

Spectrum ZX

Tandy / Radio Shack
    TRS-80 Model I
    TRS-80 Model II
    TRS-80 Model III

RP2040 Pico – some useful websites

February 28, 2021

It was a pleasant surprise to see the Raspberry Pi foundation bring out their own microcontroller, the RP2040 and also a dev board for it, the Pico.

I’ve bought a few and I can say its a really good device but what makes it standout is the quality of its documentation, it is really excellent. Never the less, there are a number of great website posts popped up for those wanting to quickly get started. There are also some gerat projects as well. I’ve listed a few of both below:

Getting started:

Official Pico Datasheet

Official Getting Started

Pi Pico Pinout and Power Pins

Getting Started with Raspberry Pi Pico using MicroPython and C

A closer look at Raspberry Pi RP2040 Programmable IOs (PIO)

How to blink an LED with Raspberry Pi Pico in C

Raspberry Pi Pico: Tutorials, Pinout, Everything You Need to Know

Scripting electronic components with Raspberry Pi Pico and MicroPython

Playing with the Pico Part 1 – Getting Started

Raspberry Pi Pico: First Impressions

Raspberry Pi goes MCU with open-spec Pico

Pico setup for Windows

Getting Started with the Raspberry Pi Pico

Getting Start with Raspberry Pi Pico

Debugging the Raspberry Pi Pico on Windows 10

Coding on Raspberry Pi remotely with Visual Studio Cod

Pico projects:

Bitbanged DVI on the RP2040 Microcontroller




How to Connect an Analog Joystick to Raspberry Pi Pico

Pi Pico, PicoProbe and VS Code

Raspberry Pi announce its own microcontroller and Pico dev board

January 28, 2021

It looks like the good people at Raspberry Pi are getting into the silicon business. They have announced their own microcontroller and a development board for it, the Pico.

Meet Raspberry Silicon: Raspberry Pi Pico now on sale at $4

ZX Spectrum Prototyping boards

December 31, 2020

After a what can only be described as a very strange year, I find myself working on a project inspired from yesteryear.

The ZX Spectrum from Sinclair Research was the first computer that I owned, getting it 1982. One of the books I bought back then was the Spectrum Hardware Manual by Adrian Dickens. I remember building many of the circuits described in it, both temporary on breadboard and also permanently on Vero board.

Now fast forward to today, December 2020. Inspired by those early days I have designed a couple of PCB’s to make building circuits for ZX Spectrum a little easier than back then.

There’s a quartet of boards: starting with a breadboard PCB, next we have a prototyping board, another more advanced prototyping board with decoding IC’s and finally a bus extender PCB with vertical and horizontal signal expansions.

As always, I’ll put them up to my Tindie shop

Blog pings and nice write ups

November 30, 2020

It’s always very heart warming when other people take an interest in what you’ve been making or what you are up to.

My recent blog entry for prototyping Feather boards got a nice write up from Gareth Halfacree across at It also appeared in the Adafruit blog.

Thanks guys !!

Yet More Feather boards

October 31, 2020

Following on from the Feather boards and Feather prototyping board I showed last time, I’ve finished a few more Feather module designs.

More Feather boards

September 30, 2020

Following on from the Feather prototyping board I showed last time, I’ve finished a few more Feather module designs.

In the picture above, on the right, we have a Raspberry Pi adapter that allows two Feather modules to be used with the RPi. The RPi’s UART, I2C and SPI are available to be used with the Feather modules. You can mixed things around if you want and have a Feather controller and Feather I/O module setup to offload real-time I/O from the RPi or just have two Feather I/O modules to expand the RPis I/O capability.

Next to the RPi adapter, with have an analogue input module using the popular 8-channel MCP3008 ADC (SPI) chip.

Next to that, we have a couple of 16-channel digital port expanders, based on the MCP23017 (I2C) and MCP23S17 (SPI) chips respectively.

As always, I’ll put them up to my Tindie shop

A Prototyping / Breadboard board for Adafruit Feather Modules

August 30, 2020

I’ve been a long time fan of the Arduino Nano and before those the Arduino Mini boards. I really like the compact Nano footprint and prefer it to the standard Arduino Due style. When I ran of computing processing power I would swap the Nano’s for the STM32 blue pill boards. So I thought I had a good choice of modules to choose from. But this has changed recently and another module footprint has entered my projects orbit.

The Adafruit Feather modules have been around for a few years and a recent project requirement saw me using their nRF52840 Express module for a Bluetooth Low Energy (BLE) based design. I liked what I saw but couldn’t find a decent prototyping solution, so I designed this prototyping / breadboard to help with getting my Feather module projects started.

The FeatherWing prototyping / breadboard has headers for a Feather module, as well as space for a 400-hole breadboard. Additionally it has PCB positions for 3x tactile switches, 3x LED’s and a FTDI style serial pin-header. Finally, all the Feather module signals are broken out to a double row header located next to the breadboard.

As always, I’ll put them up to my Tindie shop

RC2014 a simple ROM/RAM card

July 12, 2020

It’s been a while since we published any thing new for the RC2014 architecture.

This is a simple combined ROM and RAM card designed to work with the RC2014 bus. This is an experimenters board. There is no fancy memory paging etc., it’s simple memory architecture was designed to be flexible and allow the user to experiment with other CPU architectures on the RC2014 bus. It was originally designed to work with our 8052 CPU.

It features

  • enhanced RC2014 bus
  • Selectable memory* options 8K, 16K or 32K
  • Board can be used as RAM only or ROM only or both.
  • Options for nMRD/nMWR or nRD/nWR signals
  • Option for 27C512 with Hi/Lo ROM (A15) select
  • IC Decoder 74xx138 using A15/A14/A13 (with extra options for A13 & A14)
    8 or 16-bit wide data bus**
  • moveable memory positions (i.e. ROM can be at top or bottom memory space)

A couple of important notes:
* Both ROM and RAM memories must be the same size.
** see explanation below

The option for either nMRD and nMWR (nRD and nWR or’ed with nMREQ) signals or nRD and nWR only signals when IC3 (74xx32) is fitted or not fitted allows for experimenting with other CPU Read/Write architectures.

Notably, the enhanced RC2014 bus features a 16-bit data bus. The card can use this enhancement by allowing the selection of the high or low 8-bit portion of 16-bit data bus. This allows the user to experiment with 16-bit CPU’s such as 68000 or 8086 when two cards are used together.

It’s schematic is here



Microchip Power Electronics Application Notes

June 25, 2020

I’ve always found application notes to be great places to expand your knowledge and understanding. Microchip have released or rather re-released a handful of power electronics related notes this month:

Advanced IGBT Driver Application Manual

High Frequency Resonant Half Bridge

IGBT Tutorial

Introduction to MOSFETs

Introduction to Rectifier Bridges and Dual Diodes

Introduction to Rectifiers

Latest Technology PT IGBTs vs. Power MOSFETs