It’s never a good idea to let signals float around in the no-man’s land between the high state and the low state. This is why we so often use pullup and pulldown resistors. You set the line to a known, definite state by default and then switch it as necessary. Some uses of pullup and pulldown resistors are obvious. Some… Read more »
Ah well, another valuable lesson learned. The PCBs for my homemade joystick, designed to work with the BBC Micro and Master, should have been very simple. They are very simple. And yet I still managed to screw up. The PCBs for both the main adapter, which plugs directly into the computer, and the connector for the joystick arrived the same… Read more »
A major reason for doing breadboard prototypes is to learn what mistakes you’ve made in your circuit design. Of course, it’s also a way to introduce brand new errors. Or both. Before committing to fabricating PCBs, I wanted to check out whether my design for the SmartParallel dot matrix printer interface would even work. My confidence was reasonably high because,… Read more »
Okay, I lied. Having ordered the PCBs for my Centronics breakout board, and also having ordered a couple of DB25 breakout boards via Ebay, I settled in for the long wait I knew would follow. I said in an earlier post that I was getting used to these two to three-week delivery times for stuff coming from China. The truth… Read more »
Jumper cables with DuPont headers are an essential part of your toolkit. Any dabbler in electronics will have drawers of the damn things – and probably not a few wandering randomly around the workbench. But when the time comes to buy more (where do they go?) there’s always a dilemma. Do you need male-male, female-female or female-male? And how many of… Read more »
Creating a full breadboard version of the SmartParallel board is turning out not to be a five-minute affair. It has to be done meticulously and methodically if it is to have any value as a prototype. Fitting it all on to a single breadboard is proving challenging too. And that got me thinking. What about replicating at least part of… 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 »
Well that wasn’t easy. Finally, the SmartParallel TTL serial to parallel printer interface has a complete PCB layout. And I learned a few lessons along the way. The most important of these, perhaps, is that when assigning signals to the pins of a microcontroller during the schematic drawing part of the project, don’t rely on whimsy or the luck of… Read more »
In my series on ‘building’ a PC, I mentioned that a motivating factor was to have a games platform. I think I mentioned Elite: Dangerous and Kerbal Space Program. The truth, though, is that I wanted to play with flight simulators. I first took up Microsoft’s Flight Simulator when it was version 2.0 and running on DOS. I stuck with it through to… Read more »
In the first part I described the interface between two RJ45 Ethernet sockets and the BBC Micro’s analogue port. The idea behind using RJ45 connectors is that you can use any old Ethernet cable to connect the joysticks. But as these are homemade joysticks, they’ll need RJ45 sockets of their own into which one can plug the other end of… Read more »
My recent PC build was undertaken partly to allow me to play Elite: Dangerous. There was no small amount of nostalgia involved in that decision: the original Elite was one of the few games I played back in the 8-bit days. But while I can now play the two incarnations of the game – separated by 30-odd years – side-by-side, there… 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 »
Well, it looks as though this series of posts (of which this is the second and possibly last) could be badly mis-titled. For a start, it doesn’t look as though the pedal sensor of my malfunctioning e-bike is faulty. And it now appears unlikely that I’m going to fix anything – not in the near future, anyway. However, I had… Read more »
For the past four years one of my great joys has been cycling. Although of a certain age, and with not a few health issues, the advent of the e-bike has allowed me to return to one of the pleasures of my youth, as I’ve been known to blog about elsewhere. But we’re not here to talk about cycling –… Read more »