Following Ben Eater’s 6502 project – part 4

Ben Eater’s exciting 6502 project has reached the next stage – adding a display. But before I could play along, I had some remedial work to do. I’d achieved the previous stage of being able to get the LEDs to light up, but not reliably. Something was glitching and would cause the machine to go haywire. This isn’t entirely surprising… Read more »

Making ROMs for the BBC Micro

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Here’s something I’ve only just learned about the BBC Micro: you can burn ROM chips using modern EEPROMs. Who knew?* One of the strengths of the BBC Micro was the way it handled ‘language’ ROMs. The quotes are there because while many of these ROMs were, indeed, programming languages, others were applications such as word processors, spreadsheets, utilities and so… Read more »

Fun with chips #2: SN76489 sound generator IC

If there’s one sound that makes me nostalgic, it’s the brrrrr-BIP! noise of a BBC Micro being switched on. And that sound – as well as pretty much all the Beeb’s audio capabilities – can be traced to one chip – the Texas Instruments SN76489. This chip was used in a whole host of devices, including Sega consoles and arcade… Read more »

Following Ben Eater’s 6502 project – parts 1-3

No, this is not a post about stalking. I’ve been toying with a design for a simple 6502-based homebrew computer for a while now. I’ve built a kit and am in the middle of laying out the schematic for the first board for my own design. So I was thrilled when Ben Eater, one of the best educators on YouTube,… Read more »

SmartParallel: troubleshooting with logic analyser and scope

Well, it does seem that the problem I’ve been having with the SmartParallel board is indeed that horror of horrors – the intermittent fault. Or perhaps something weirder. This is some kind of quantum device – it works only when being observed. Setting up a server The SmartParallel was working perfectly for a few days. Then I didn’t use it… Read more »

SmartParallel: tracking down a problem

Hmm… maybe I spoke too soon. No sooner had I congratulated myself on a completed project than a problem raised its ugly head. And it was one that required some tracking down. And so, as this blog is my lab notebook, I thought I’d share what happened, as I always find other people’s tales of troubleshooting to be illuminating. One… Read more »

SmartParallel: mission accomplished

It’s done. For now. After weeks of dithering, I finally got around to making up one of my SmartParallel serial-to-parallel printer interface PCBs. I chose to solder the components – mostly surface mount – by hand and that went easier than I expected. The only snag was that it didn’t work. Not right away, at least. And finding out where… Read more »

Building a photo digitiser

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Regular readers will know that, in real life, I’m a photographer. And I’ve been one for a long time, which means many of my images were shot on film. They’re not going much good just sitting in filing cabinets – I need digital copies, which is where this project comes in. But first, some caution is required: if you like… Read more »

Rat B@stard mk.1 – a rodent scarer

They’re back! It could be squirrels. Maybe mice. Possibly rats. But whatever they are, the bastards are making themselves at home in the engine compartment of the car again. We had this with the Citroen C5. Twice the twitchy-nosed little feckers chewed through the cables for the top-dead-centre sensor, leaving the car in a state where it would turn over… Read more »

6502 homebrew: display and keyboard problems

The Apatco 6502 breadboard computer kit I’ve been building is complete. The next stage was to make it more so. A word of warning, though. This story does not have a happy ending. Nonetheless, someone may find the attempt at debugging entertaining or instructional, so here it is. The kit is sold (or perhaps ‘was’ would be better, as it… Read more »

6502 homebrew: the software toolchain

Now that the Apatco kit is working – at least the basic version (having trouble with the keyboard and display upgrade) – it’s time to mess around with writing code for it. Many people swear by the now-abandoned CC65 as their compiler/assembler of choice for 6502 homebrew computers. But I’m going with Beebasm. Although inspired by and largely aimed at… Read more »

6502 homebrew: debugging the kit #2 [solved]

If in doubt, start again. That’s not a real saying, but it should be. As we saw in the last post, the Apatco 6502 breadboard computer was finally wired up but refusing to work. I’d fixed my faulty ROM code, buzzed out all the address and data lines to check they were connected correctly and determined that the reset circuit and… Read more »

6502 homebrew: debugging the kit #1

Okay, so it was time to deal with something that has been nagging at me for a while. I have this Apatco kit 6502 breadboard computer kit and never quite got around to finishing the basic setup. It takes a lot of wiring. I just got tired, put it in a box and shoved it in the projects cupboard. For… Read more »

Arduino: running hard to stand still

Don’t you hate it when something that was working stops? You can safely bet that it’s because, somewhere along the way, something has been ‘improved’. I needed to make a change to the code running on a couple of IoT room thermometers. These are built around the Adafruit Huzzah ESP8266 board (the non-Feather version). And they’ve been running flawlessly for months…. Read more »

IR remote control for the home – part 3

In the previous two posts, we set up an ESP32 development board with an IR receiver to read codes sent by a remote control. Now it’s time to add MQTT capability. I chose the PubSubClient library – available in the Arduino IDE library manager – because it claims compatibility with the ESP32. When I looked closer, it turns out that… Read more »