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Getting By

Getting By

A simple repository of largely nonsensical wittering. It may (or may not) be to do with what the Batsocks lot are currently using their Idle cycles for.

Angband + Raspberry Pi

Raspberry Pi Posted on Wed, June 06, 2012 18:32:47

I’ve had to set up a rota to use the Raspberry Pi. 1 hour each.
Someone… (ok – mea culpa) found that a simple

sudo apt-get install angband

will install a great rogue-like dungeon crawler.

I used to play this on my Archimedes 20-odd years ago and it’s still just as addictive.
No – it’s not 3d. No – it’s not fast. But holy-moley, it’s addictive.

We could stop at any point. Of course.

Packaging Pleasure

Electronics Posted on Fri, March 16, 2012 14:55:39

In the past few weeks, I’ve received a couple of parcels which tickled me. They demonstrate the different ends of the packaging spectrum, so I thought I’d share some pictures.

Firstly, some Mega8A tqfp’s that I bought on eBay from a Hong Kong seller. The are the cheapest Mega8’s I’ve ever bought – superb value at around 80p each (including postage). As you can see, they’re minimally packaged. A padded envelope containing a zip-top plastic bag with the bare chips loose inside. Amazingly, all the legs look undamaged and relatively flat (important for reflowing).

Secondly, a couple of XMegaA3’s I bought from Farnell – one XMega192A3U and one XMega256A3U. These are 64 pin 0.8mm pitch tqfp’s. Farnell aren’t the cheapest supplier of these chips (especially in small quantities), but they have a low minimum order limit and have a UK base, so are pretty quick to deliver (a couple of days). These arrived in a huge cardboard box. In the cardboard box, surrounded by crumpled brown paper, were two waffle-trays, each vacuum packed in metallised plastic anti-static bags.
vacuum packed metallised bags.

desiccating bag

Just one chip per waffle tray

I am NOT complaining about inappropriate packaging here – quite the opposite. Each supplier delivered exactly as I expected. I’m delighted to have these diverse sources of parts available to me.

Re-sealing the metallised plastic bags
Since I’m not going to be using the XMegas for a couple of weeks (I’m waiting on a set of boards from iTead), I re-sealed them in their bags using a smooth-tipped soldering iron on high. Running the iron along a metal ruler gives a nice straight edge.

Paste. Populate. Reflow.

Electronics Posted on Thu, February 02, 2012 20:42:26

I took some photos whilst doing a recent batch of XMega PDI boards.
I was pleasantly surprised how well my camera caught the action…

Paste applied by stencil:
Notice the advanced (and purely by chance) side-lighting used to capture the depth of the paste. The polyester stencil was supplied by – who I’d recommend highly; lightning fast-turn around and a superb price.

Components populated:
You might think that the general mashing and smudgyness of the paste (caused by shaky-handed parts placement) would cause problems upon reflow, but that’s not the case at all.

I just wish that I’d got a way of videoing the reflow process. It’s magical the way all the parts shuffle and hunker down to the middle of the pads by the force of surface tension.

In case that’s not enough close-ups for you, here’s a couple of bonus 1:1 pictures, unmolested from the camera:
The grainyness to the paste is the individual balls of solder. Bear in mind that these pads are 0.8mm apart.

Not bad for home reflowing!

greyscale POV!

Electronics Posted on Mon, December 19, 2011 22:12:47

I’ve just thrown together a little demo for an XMega…

It’s a 4bpp (bits per pixel), 16 pixel high POV (persistence of vision) image generator.

It’s just 16 LEDs connected to an XMega32A4.

The program steps through each slice of a bitmap (held in flash memory). For each slice, it toggles the 16 LEDs rapidly on/off to produce the light intensity required for each pixel. For gamma correction, it maps the 4bpp source brightness to a 6bpp output. The output is encoded as binary-coded-modulation.The whole pattern repeats itself when it gets to the end of the bitmap.

Here’s a picture of the resulting effect:

And here’s the original bitmap I used (before adding a strange blob for testing purposes)

Amstrad NC100 fuse

Electronics Posted on Wed, May 25, 2011 12:51:26

After throwing out my Amstrad NC100 in a big loft-clear out several years ago, I decided that I wanted one to play with again! Ebay came to the rescue with a (non-working) replacement. Fixing my new nc100 was relatively easy – the internal fuse had blown. As a temporary fix, a 0R 1206 worked very nicely. However, I’ve recently had to order some parts from Mouser, so included a suitable fuse…

Here are a couple of pictures of the new fuse being put in place…

Old 0R “fuse” removed…

New 0.8A fuse in place…

I can now sleep easy.

Tiny ISP Adapter

Electronics Posted on Mon, March 07, 2011 11:07:13

A quick and easy ISP adapter for an 8-pin AVR (Tiny13/25/45/85s)

I’m in the middle of designing a simple 8 LED meter/cylon sweep/POV kit.
At it’s heart is a socketed Tiny13 (although I’ll probably end up with a T85).
Because there’s no room for an ISP header, I’ve been pulling the chip out of the socket each time I want to reprogram it (and I do that a lot when I’m developing code).

That was getting rather tiresome, so I’ve made myself a daughter-board that plugs into the socket…

It’s just a normal turned-pin IC socket. I’ve drilled the holes in the board larger than normal, so the socket sits flush with the board (they usually sit proud). That means the legs extend just far enough on the underside to insert into the main board’s socket…

It works nicely, and has significantly reduced my code / compile / reflash / find_stupid_error development lifecycle.

From Tones to Tunes…

Arduino Posted on Tue, November 16, 2010 00:05:47

Simple things always tend to get complicated…

I wanted to update my ‘Still Alive’ Arduino demo. This currently uses a simple square-wave on pin 8 to generate a melody. I wanted to make a simple change so that I could also play a bassline on the same output pin as the melody.

Idea 1
Chop-mix between two square waves (with different frequencies) to produce two clean, clear tones at the same time. It’s as simple as outputting one cycle of square-wave at frequency A followed by one cycle at frequency B.

Unfortunately, it sounds horrible in practice. It just doesn’t work.

Idea 2
Rather less simple.
Use a high-frequency PWM and let the speaker perform crude filtering. This gives a rudimentary Digital to Analogue converter. Produce two notes by mathematically mixing their waveforms.

Fortunately, this method works really well. It’s more complex that the ‘chopping’ idea, but it’s worth it. I’ve now got a two-channel, envelope shaped, wave-table audio output from a single pin.

I’m hoping to get it polished and scrunched back into the demo soon. The addition of a bassline really makes a huge difference. [edit: Here’s the youtube video]

Oh, and because anything is more interesting if it’s got a picture, here’s a graph from my waveform generating spreadsheet…

Polygon Scanline Conversion

TellyMate Posted on Mon, October 18, 2010 15:19:48

Over the past few weeks, I’ve been playing with some polygon scanline conversion routines for a new ‘TellyMate’ demo…

Here’s an example of the new Arduino logo…
(Sorry it’s an image – my blog software doesn’t seem to be able to do fixed-width text?!)

This is rendered from 73 bytes of vector-based flash data.

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