Category Archives: Projects

Dot matrix printing the easy way

Twice now I’ve declared my SmartParallel project completed, and twice it has proven to be faulty – or, at least, difficult. I’m still plugging away at it (more on that soon), but in the meantime I really wanted to be able to print out 6502 assembly code listings on my Epson MX-80 F/T III dot matrix printer. And then I… Read more »

Zolatron 64 – first PCBs

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Well, how exciting. The first versions of the PCBs for the Zolatron 64 6502-based homebrew computer have arrived, and they are very pretty. Which is just as well… I say that because at least some of these boards will serve no purpose other than as decoration. I’d made some mistakes – one annoying, one stupid but survivable, and one idiotic… Read more »

SmartParallel dot matrix printer server – redux

Well, it had to happen sometime. I finally killed a Raspberry Pi. Not on purpose, of course. I’m not a psycho. (I’ve been tested.). Nope, it was just sheer impatience and stupidity. But we’ll get to that in due course. First, let’s talk about finishing a project that was already finished. Just when you think you’re out… Sometimes you think… Read more »

Zolatron 64 6502 homebrew – moving up to real hardware

You can only go so far with a breadboard. Those things are great for quick and dirty prototypes and experimentation. But there comes a point when a breadboard is an unhealthy basis for a project. And yes, I’m aware that many people have followed Ben Eater‘s lead in building 8-bit processors and 6502-based computers on breadboards. I include myself among… Read more »

Zolatron 64 6502 homebrew – processing commands

In an earlier post, I described how I was parsing commands input (via serial) into the Zolatron 64 8-bit homebrew computer in assembly language. That parsing process matched an input command with an internal list and the result was a ‘token’, a single integer value of $80 or more representing that command that is placed in a memory location. Or… Read more »

Zolatron 64 6502 homebrew – parsing inputs in assembly

Okay, so this is going to be a long one. Grab a coffee, settle down and we’ll begin… The last time we talked, I was able to send messages to the Zolatron 64 6502 homebrew computer via its serial port. But all it could do was print those messages to the LCD screen. It’s time to actually do something with… Read more »

Zolatron 64 6502 homebrew – a terminal of my own

Early on in the design of the Zolatron 64 6502-based homebrew computer I made the decision that I wasn’t going to bother with attaching a keyboard and monitor. It has a 16×2 LCD display for small stuff. Otherwise, I/O was always going to be via serial. That means talking to the machine via some kind of terminal software. To date,… Read more »

Zolatron 64 6502 homebrew – converting between text and numbers in assembly

One thing it was obvious I would want to do with the Zolatron 64 6502 homebrew computer is have a routine to display the contents of sections of memory – à la Wozmon. There’s a snag, though. The content of any given byte in memory is a number, in the range 0-255. But to display this on the screen, this… Read more »

Zolatron 64 6502 homebrew – better LCD printing

A quick recap. The Zolatron 64 6502 homebrew machine is at the point where it can print messages to an LCD screen and send and receive messages via the serial port. Most of the time. The incoming messages are put in a buffer and then printed to the LCD. And a fat lot of use that is. I wanted to… Read more »

Zolatron 64 6502 homebrew – serial port part 3

Listening is so much harder than talking, don’t you think? That’s how it turned out with the Zolatron’s serial port, anyhow. Getting the computer to send messages was pretty easy. Receiving them? Not so much. The first stages of developing the software were typical. I wrote code that I knew should work. It didn’t. I cursed the binary gods for… Read more »

Zolatron 64 6502 homebrew – serial port part 2

It didn’t work. Not straight away, anyhow. Once I’d wired up the 6551 ACIA chip, my UART of choice to give the Zolatron 64 a serial port, I threw together some code to test it. It was pretty simple – it took my already known-good code that prints a message to the LCD and added to that a routine to… Read more »

Zolatron 64 6502 homebrew – serial port part 1

So far, the Zolatron 64 6502-based homebrew computer has output (a 16×2 LCD screen) but nothing in the way of input. I have toyed with the idea of getting it to output to, say, HDMI using a Teensy as an intermediary. And also of giving it a PS/2 keyboard input (the latter still being a possibility). But in the end… Read more »

ESP32 room thermometer: with 18650 battery level indicator

It seemed like a good idea at the time. The TTGO ESP32 microcontroller board that I’m using for a room thermometer project comes with a battery connect and charging circuitry for a Li-Ion cell. It would be so much easier to deploy the thermometer if I could run it off a battery. And it works. Kinda. There are issues, though…. Read more »

Battery-powered ESP32 IoT room thermometer with OLED display

A while back, I made a couple of ESP8266-based room thermometers. These have been beavering away happily ever since – one on the desk in my office and one in the living room (or salon as we say in France). The only significant change I’ve made to them is to add the capability for them to report temperatures to an… Read more »

The Dawnclock – back from the dead

I’d been waiting for this moment. I’m not a electronics or coding expert and so, sooner or later, I expect all of my projects to die. But the Dawnclock just kept on living – right up to the point when it didn’t. I first blogged about this project in January 2013, which means that it’s been operating for eight years…. Read more »