Mar 282013
Guzunty Pi - Open Source CPLD board for the Raspberry Pi

The Guzunty Pi board is an open source Complex Programmable Logic Device (CPLD) add-on for the Raspberry Pi. Derek Campbell is behind this project, and has clearly spent a lot of time and effort putting it all together. He describes it… “a CPLD is like several large breadboards laid out on your desk, full of every combination of logic devices you are ever going to need. It is waiting to be told what to do. It doesn’t need a host of jumper wires like a breadboard would. It can be reprogrammed again and again (even […more…]

Mar 252013
The leaning header of Pi5a. How best to solder a header on P5?

People seem very reticent about soldering headers to their Pis. Nobody else seems to be blogging or vlogging about it.* D’you know what? I think it was a really magnificent oversight that the original Raspberry Pis shipped with the 26 pin GPIO header on. In case you didn’t know, the original plan was to leave them off, but they didn’t get deleted from the design before the factory quoted for manufacturing – and they’ve stayed on ever since. Without that happy accident, I don’t think I would have ‘gotten’ so heavily into interfacing. You see, […more…]

Mar 222013
How to use interrupts with Python on the Raspberry Pi and RPi.GPIO - part 3

Multiple threaded callback interrupts in Python We’ve been learning about interrupts this week because of the brand new interrupt capabilities of RPi.GPIO. We covered a simple “wait for” interrupt in part 1, threaded callback interrupt and button debouncing in part 2 and today we’re getting sophisticated with multiple threaded callbacks. “WoooooooooOOOOOOOOOOOOOOOooooooooooo”, I hear you say. ;) Well actually, we’re not doing much that’s very different from last time, except, now there’s more of it. We’ll add another button and another threaded callback function the same as the first one (but on a different GPIO port). […more…]

Mar 202013
How to use interrupts with Python on the Raspberry Pi and RPi.GPIO - part 2

Interrupts are an efficient way for a program to be able to respond immediately to a specific event. In the previous article I explained the basics of using interrupts in RPi.GPIO and gave an example of a simple “wait for an event” interrupt program. In this second article I will introduce “threaded callback” which opens up a lot of new possibilities. Threaded callback – what the heck is that? I know it sounds complicated. And it probably is complicated in the C code it’s written in, but we’re Pythonites and we don’t have to go […more…]

Mar 172013
How to use interrupts with Python on the Raspberry Pi and RPi.GPIO

The latest big news in the world of Raspberry Pi Python GPIO programming is that Ben Croston has released an update for RPi.GPIO. Why is that a big deal? Because this version has interrupts. “What’s an interrupt?” I hear you say. It’s a way of waiting for something to happen without checking constantly whether or not it’s happening. Imagine that you’re waiting for a delivery – something you’re really excited about – like a Pi camera.You spend far too much time looking down the street in eager anticipation of the postman’s arrival. You can’t fully […more…]

Mar 142013
Eben Upton meets at Oxford Geek Night

Last night I went along to the Oxford Geek Night #30 to see Eben Upton talking about the Raspberry Pi. It was a good evening, but it was absolutely wall-to-wall people. Fortunately, it was obvious that it was going to be busy, so I got there very early and got a seat at a table near the stage. But you can be too clever sometimes can’t you? The fact that there were so many people ‘standing in the gap’ meant that I couldn’t see the stage. :( I enjoyed Eben’s talk though. The sound system […more…]

Mar 112013
How to make your own Raspberry Pi flag-waving demo

After the recent call for items for the demo table over at Raspberry Pi HQ, I thought I’d send over a flag-waving set. It’s not a product for sale, but it’s one of the most eye-catching and memorable Raspberry Pi demos I’ve made. People mention it more than any of the others when I don’t take it along to Jams. There’s a video, at the end of the page, showing three Pis all waving flags together (based on three different drive systems). Making the flag So I set about making a flag. It’s pretty easy. […more…]

Mar 052013
Controlled shutdown duration test of Pi model A with 2 cell lipo

Lithium polymer batteries are light and powerful, but they can’t be run completely flat or they are ruined. I’ve been using them for several years to fly model planes, so I have plenty of them around. I’ve also been using them at Raspberry Jam meetings to power some of my Pi demos. I thought it would be fun to make a circuit so the Pi could monitor its own battery voltage. I used an analog to digital converter (mcp3002) and had the Pi check the battery voltage every minute and shut down when the battery […more…]

Mar 012013
Raspberry Pi in near space 35.5km from earth

On Wednesday of this week, I went to film Dave Akerman and Anthony Stirk launching two high altitude weather balloons. One of them had a Raspberry Pi inside a TARDIS as its payload. It was cold. In the video you’ll see it looks almost as if Dave is smoking at one point. That would have been a bad idea as the 70 kg red cylinders are full of highly explosive Hydrogen gas. Slight cheating on the Vid I confess in advance that I did have to cheat slightly with the video. Dave was really keen […more…]