I left the project in the previous post with a ROM on-board, but still running NOPs – it was running an EEPROM filled with zeros. The next step is to find a way to run programs and see the output. In order to do that I will need to do a few things: Add an STM32 ‘Blue Pill’ microcontroller to handle I/O Add an LCD display module to output debug information from the STM32 Add …
One of the demos I’ve carried across nearly all the platforms I’ve worked on is the rotating cube demo, typically with back-face culling (hidden line/face removal), perspective, and fast integer maths. The code has been ported to the Gameboy, CPC, PC, Atari ST and Scratch. On more capable systems I usually add filled-in polygons with simple texture mapping and Gouraud shading I first wrote this demo around 30-odd years ago for the Spectrum, and I …
The Spectrum screen handling is not the most straightforward and, with lack of hardware sprites, scrolling, and an awkward layout, can be intimidating at first. This post details how I managed to scroll a 24×24 character block of tiles on the Spectrum within one VBLANK interval. The scroll routine employs a number of tricks to achieve this by: Using the stack pointer (SP) to fetch tile data and push it to the screen. Using self-modifying …
I’ve been using the ZXSpin emulator for a while now to develop code on the ZX Spectrum. This has many advantages, namely an integrated assembler and disassembler, but quite a few quirks, and the editor, whilst adequate for small projects, is not really up to scratch for large ones. In addition, my main machine is an old Macbook, so have to boot into Windows on it to do any software development. My criteria for the …
I’ve been writing a smooth scroll routine for the ZX Spectrum over the last few days, based upon my recollection of conversations I’d had with Mike Follin at Software Creations whilst he was developing LED Storm and Ghouls ‘n Ghosts. The code is written purely in Z80 assembler and demonstrates the following techniques: Using the stack as a quick way to read and write blocks of data Using the vertical blank interrupt to run a …
