Oli's old stuff

Tinkering with retro and electronics

Nov 12, 2021 - 9 minute read - spectrum amstrad cpc z80 retro gamedev smeg

Image compression in SMEGv2

Image compression in SMEGv2 There’s a few technical differences between SMEG v1 and the current v2 (SMEGCPC) codebase; most of which come about from looking at the original problems in a different way and tackling them without the burden of existing code. One of the “big” ones to talk about is how I am dealing with background images for the scenes. In both versions the “stage” area is 240x128 pixels (or 30x16 char cells).

Oct 27, 2021 - 7 minute read - spectrum cpc z80 retro gamedev smeg

Rebooting SMEG for the Amstrad CPC

Out with the Old I recently started messing about with the Amstrad CPC 464 to learn how to code on it. Specifically questions such as “how does the screen ram work?”, “how do I move software sprites?” and “how does input work?” etc. To speed up this I wrote some code to convert some of my early SMEG sprites into CPC pixel format and started plotting them and moving them around.

May 12, 2021 - 5 minute read - spectrum z80 retro gamedev smeg

What happened to SMEG?

What happened to SMEG? Chances are that a bunch of people reading this post will remember SMEG. Either from the introduction blog entry, the posts on twitter, the itch.io page or maybe you even pre-alpha tested the demo I put out to a couple of insiders. I originally started the project in November 2019 as a way of learning Z80 assembly and the ZX Spectrum hardware. I was (and still am) extremely excited by the idea - a point and click adventure game and system designed for the Speccy.

Feb 6, 2021 - 7 minute read - sinclair electronics retro hardware zx spectrum zxsprite

ZX-Sprite Hardware Prototype - Part 2

ZX-Sprite This is a short series about exploring ZX-Sprite, a fantasy hardware add-on for the ZX Spectrum that aims to bring Spectrum Next style sprites to the 48K and 128K systems. The series ZX-Sprite Introduction ZX-Sprite Prototype - Address decoding ZX-Sprite Prototype - Baremetal Pi GPIO (this post) Going Baremetal Last time we went over how to use a GAL22v10 to decode the 3 ports we need to control the sprite system.

Feb 5, 2021 - 9 minute read - sinclair electronics retro hardware zx spectrum zxsprite

ZX-Sprite Hardware Prototype - Part 1

ZX-Sprite This is a short series about exploring ZX-Sprite, a fantasy hardware add-on for the ZX Spectrum that aims to bring Spectrum Next style sprites to the 48K and 128K systems. The series ZX-Sprite Introduction ZX-Sprite Prototype - Address decoding (this post) ZX-Sprite Prototype - Baremetal Pi GPIO Introduction The last post introduced the idea of ZX-Sprite, a port of the Spectrum Next’s sprite system to the ZX Spectrum hardware.

Feb 5, 2021 - 9 minute read - sinclair electronics retro hardware zx spectrum zxsprite

ZX-Sprite Introduction

The series ZX-Sprite Introduction (this post) ZX-Sprite Prototype - Address decoding ZX-Sprite Prototype - Baremetal Pi GPIO ZX-Sprite: An Introduction Towards the backend of 2020 I started working on a Spectrum Next game; the game uses a couple of the cool features of Next - tilemaps and sprites. As a bit of fun, I started to adapt my emulator to support both of these; mostly because I’ve got into a bit of a nice workflow with this emulator; one that I can’t quite get from CSpect.

Sep 20, 2020 - 8 minute read - sinclair electronics retro hardware zx81

ZX81 hardware hacking - Homebrew ZX8-CCB

ZX81 Hardare Hacking - Homebrew ZX8-CCB In my last post I talked about the problems associated with the video signal that the ZX81 outputs. There are various mods that can correct this, with one of the leading ones being the PokeMon ZX8-CCB. In this post I’ll explore a homebrew hack that aims to recreate the ZX8-CCB for fun and educational purposes. DISCLAIMER This is not endorsed or associated with the original ZX8-CCB project in any way.

Sep 19, 2020 - 8 minute read - sinclair electronics retro hardware zx81

ZX81 Video Conditioning Mods

ZX81 Video Conditioning Mods The ZX81 is notorious for outputting an RF signal that modern TVs struggle with. This is a post that explores the video signal from the ZX81 and discusses a few of the mods for improving it. ZX81 Composite Mods Modern TVs have issues with the ZX81 RF signal, and most common solution is for people to modify their ZX81 for composite video out. Knowing nothing about the subject, I rushed out and bought a kit from tfw8bit.

Sep 6, 2020 - 8 minute read - spectrum electronics retro hardware 4116 ram

ZX Spectrum 4116 RAM Replacement Board - Part 2

Building a ZX Spectrum Lower Ram Replacement Board - Part 2 In my last post I talked about the broadboard prototypes of my attempt to build a Lower RAM replacement for the ZX Spectrum. It was encouraging to see that something could work on a breadboard, even if it was glitchy. The long wires and extra capacitance would cause a lot of noise for something that needed to be accessed as frequently as RAM.

Aug 14, 2020 - 7 minute read - spectrum electronics retro hardware 4116 ram

ZX Spectrum 4116 RAM Replacement Board - Part 1

Building a ZX Spectrum Lower Ram Replacement Board - Part 1 As I mentioned in my previous post on messing around with Arduino and 4116 DRAM, the ZX Spectrum is prone to failures of the lower RAM. Many people (myself included) choose to replace a failed 4116 RAM chip with a modern replacement “board” that uses SRAM instead of DRAM. The reasons are clear, modern boards are made using readily available components - even “new” 4116 chips are all old stock and 30-odd years old.