Well the Zolatron 64 homebrew 6502 computer is getting spiffed up in all sorts of ways. So here’s a quick catch-up before the next big challenge. Backplane The original backplane has been working fine. But I decided to upgrade it anyway. The connectors for the boards were a little further apart than they needed to be. And the new backplane… Read more »
Another day, another lesson learned. My Zolatron 64 6502-based 8-bit computer uses serial for its main I/O. One day I may add video output and keyboard input. But for the time being, I’m happy to talk to it via a terminal from another machine. So far, that other machine has been my electronics workbench computer – a LattePanda Alpha. And… Read more »
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 »
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 »
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 »
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 »
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 »
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 »
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 »
I was pretty pleased with my serial level shifting board – right up to the point where I tried to use it. The tl;dr version of this post is that the board works, but not well enough. It has severe limitations that, I think, make it useless for the intended purpose. Let me explain… Voltage levels The purpose of the… Read more »
Hmm, yes, clearly it wasn’t going to be as easy as all that. While creating the PCB layout for the SmartParallel serial to parallel printer interface, I shuffled a few of the pin assignments on the Atmel ATMEGA328PB microcontroller. The reason was simply to make routing a tad easier. But I had a nagging feeling that this might cause a… Read more »
Not every device speaks the same voltage. In designing the SmartParallel serial-to-parallel printer adapter, I chose to use 5V as the VCC supply throughout the board. But I was constantly aware that some of the devices that might talk to the board – such as the Raspberry Pi – use 3.3V for their I/O. What to do? There’s only a… Read more »
The SmartParallel, aka DottyMatrix, project has been languishing for a while now, but it’s time to get it restarted. SmartParallel is a serial-to-parallel interface that I embarked on because I wanted to be able to use my decades-old Epson MX-80 F/T III dot matrix printer with a number of platforms that don’t have parallel interfaces, such as the Raspberry Pi…. Read more »
Although it was gratifying (and surprising) that my DottyMatrix serial-to-parallel interface worked as soon as I plugged it into an actual printer, there was one nagging flaw. And that was a lack of acknowledgement. The /ACK signal in the Centronics interface was often sadly neglected, if not ignored completely. But in theory, the sequence for printing a character goes like… Read more »
It seems the repairs to my venerable Epson MX-80 F/T III dot matrix printer did actually work because it’s now printing again! What’s more, it’s printing via the prototype of my DottyMatrix serial to Centronics parallel interface. Time for a quick recap. The DottyMatrix is based around an AVR ATMEGA328PB microcontroller. It takes input on a TTL-level serial connection and… Read more »