Monthly Archives: July 2019

SmartParallel: serial shifter issues

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 »

Fun with chips: #1 MC1441 bit rate generator

I’m easily pleased. Leave me alone with a breadboard, multimeter, oscilloscope and a previously unencountered IC, and I can amuse myself for hours. Well, minutes anyway. It’s fun to fire up a chip and watch it do its stuff. And even more fun if it’s an old chip. But before we get to the IC itself, let’s fill in some… Read more »

SmartParallel: laying out the PCB

We’ve been here before, but now it feels like we’re finally getting somewhere. The long-running saga that is my SmartParallel serial-to-parallel dot matrix printer interface is nearing completion. Well, maybe. Having solved (I think) the back-powering problem, and with a prototype that I believe actually works, I’ve decided to call Rev 2.0 of the design schematic the final version. All… Read more »

ATMEGA328PB breakout and prototyping board

The first thing I did when I progressed from Arduinos to programming Atmel 8-bit microcontrollers in the raw was build a programming and prototyping board. [BTW, for once, this is not going to be a multi-post project. I’m putting a bit of background here, but will put full, constantly updated details on the GitHub page.] Arduinos make it easy for… Read more »

DIY joystick for the BBC Micro – part 6 – completed (definitely)

Just when you thought it was over… When we last saw this project it was complete except for stuffing the joystick into some kind of box. As that kind of mechanical stuff doesn’t interest me greatly (and I’m crap at it), I wasn’t going to bother with a post about this final step. But hey, I’m nothing if not a… Read more »

SmartParallel: curing the back-powering problem

And so back to the back-powering problem on my ever-imminent SmartParallel interface board. The issue is that, when the printer is powered on but the SmartParallel board isn’t, voltages coming from the printer via signal lines being held high are part-powering the board. One option was to simply ignore this problem. I find that works for a lot of things… Read more »

DIY joystick for the BBC Micro – part 5 – completed (pretty much)

Having got impatient waiting for my PCBs to arrive from China, I went ahead and cobbled together some interim solutions for this project. And what happens? The PCBs arrive the next day. These are the ‘fixed’ PCBs with the proper footprint for the DB15 connector. And what can I tell you? They work. There is one slight issue that I… Read more »

DIY joystick for the BBC Micro – part 4 – a quick lash-up

While waiting for revised PCBs to arrive from China, I figured the time would be well spent learning a little more about the BBC Micro’s analogue port. And I have taken delivery of a couple of DB15 breakout boards, which meant I could try wiring up the joystick, albeit in a crude and temporary way. One joystick needs to send… Read more »

SmartParallel: mystery solved

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Although the stripboard version of the SmartParallel board is working, one niggle remained. When the printer was switched on, but the SmartParallel board wasn’t powered, I was getting random resets of the printer. They weren’t as frequent as with the breadboard prototype, but they were there, sometimes. Also, there was a problem with signals effectively ‘back powering’ (I’m not sure… Read more »