45 Minute Project – £4.10 XBMC Remote Receiver

I’m a big fan of XBMC, and have an Ouya running XBMC set up in my lounge, streaming from my NAS. I normally use XBMC remote on my phone for controlling it, but this gets annoying when the phone is on charge, or I’m using it for something else.

I noticed that the majority of my TV remote is completely unused when the TV is in HDMI mode, and had a bit of a lightbulb moment!

Almost none of these buttons are used!

I already had an Arduino Pro Micro (£3) lying about i’d bought for testing out as an upgrade path for the minimus based projects i’ve been playing with.  It is leonardo compatible, small, cheap and pretty easily available.  I added an IR Receiver (£1.10) to the weekly Hackspace Farnell order to complete the parts list.

The pinout of the IR receiver makes it very easy to connect to the pro micro, using the RAW (VUSB), GND, and A3 pins.  I just bent the OUT pin (pin 1) on the receiver to the left a bit as follows:


The body of the receiver fits perfectly behind the USB plug, flat against the voltage regulator.  I used the IRremote arduino library to grab data from the remote using the IRrecvDemo sketch and mushed some buttons:


My remote uses 0xFFFFFFFF as a ‘key repeat’ code, about every 200ms when the button is held down. I found that in practice I had to ignore the first of these, as it was repeating way too fast and doing double presses.

I tweaked the IRrecvDemo sample code, added in a bit of keyboard and came up with some working code:


int RECV_PIN = A3;

IRrecv irrecv(RECV_PIN);

decode_results results;

int key;
int count;

void setup()
  irrecv.enableIRIn(); // Start the receiver

void loop() {
  if (irrecv.decode(&results)) {
    switch (results.value)
      case 0x8B452AD: // up
        key = KEY_UP_ARROW;
        count = 0;
      case 0x8B410EF: // right
        key = KEY_RIGHT_ARROW;
        count = 0;
      case 0x8B4D22D: // down
        key = KEY_DOWN_ARROW;
        count = 0;
      case 0x8B4D02F: // left
        key = KEY_LEFT_ARROW;
        count = 0;
      case 0x8B4926D: // enter
        key = KEY_RETURN;
        count = 0;
      case 0x8B412ED: // red
        key = KEY_BACKSPACE;
        count = 0;
      case 0x8B4B24D: // green
        key = ' ';
        count = 0;
      case 0x8B44AB5: // yellow
        key = KEY_ESC;
        count = 0;
      case 0x8B450AF: // blue
        key = 's';
        count = 0;
      case 0xFFFFFFFF:
        key = -1;
    if ((key != -1) && (count!=1))  // if count = 1, it is the first key repeat, so ignore it.
    irrecv.resume(); // Receive the next value

Total cost £4.10, total time 45 minutes. Sorted!


New Robot – Chassis Printed

Last night I retrieved the first chassis printout and did a test assembly with the parts that have arrived.  It looks good!

The axle distance is perfect, the chunks I carved out for the pi are all the right sizes, and it looks bitchin.  The only negative was that the mount for the raspberry pi camera was slightly too small, but I managed to modify it enough to fit with some snips and needle files.  I’ll modify it slightly for the final print, including adding some LEDs for lighting up the area in front of the camera.

Next step is to print the top chassis (currently in progress) and design a PCB for power regulation and monitoring, motor control, and other IO.

New Robot – First Printed Parts

Before leaving the hackspace on saturday, I set the wheels and motor mounts for my robot printing, as I figured these parts probably wont change while I finish the rest of the design.


Tonight, I cleaned up the printed parts, and did a test assembly of the track sets:


They looked about right, so I set the first version of the chassis printing before I left. Hopefully its right, as each chassis half costs about £4 to print!


PHPExcel Conditional Formatting Empty Cell

I’ve spent about an hour trying to get this working, so i’ll post it here.

To get a spreadsheet automatically marking any empty cell in a column in dark red, use the following incantation:

$conditional = new PHPExcel_Style_Conditional();

3D printing – Bandsaw Fence

I spent some time earlier in the week getting the bandsaw at Hackspace Manchester working, so now its cutting again!  The main problem with the bandsaw is cutting straight, as it was an ebay purchase it diddnt come with a fence, so there was nothing to run the cut material against.  This model of bandsaw hasnt been made in around 30 years, so trying to buy a new one will be impossible, and ebay is too much hard work.

Though we do have a 3d printer… and a workshop.  Idea!

Step one was to have a look at the bandsaw.  It has a channel running along the front , so I took some measurements to see what I was working with.



So, i had the measurements, it was time to take to my CAD software and design something to fit in the channel.  My choice for this is OpenSCAD.  I used it to first create the shape of the channel, then to carve this shape out of a block.



I extruded this to a few mm wide, then printed it to test.  There was a bit of tweaking needed to get it to fit exactly, so i ended up doing 4 iterations with the sizes tweaked slightly.




Once i had one that fitted, i printed it out extruded to 20mm to check it would fit and slide correctly.


It did, so i moved onto designing the actual fence.  Step one was to cut some aluminium extrusion to size, and measure it.  A month or so ago I had managed to womble a nice straight piece of 16mm x 16mm  3.2mm thick L channel, which was pretty much the perfect size.  I cut this to size, and modelled it in openscad.


The actual cad modelling took a couple of hours of tweaking, but i the above picture shows the basic steps.

First off i extruded my clamp to 50mm wide, and added a wedge to the side of it.  50mm gives enough width for it to sit in the runner, and counteract twisting force from the back of the fence being pushed on.  The wedge is to give support to the top part of the L channel.

Second, I added two captive nuts and holes for M5 bolts.  Mainly because we have a massive bag of M5 hex-head bolts that are perfect for printed thumbscrews. Theoretically i could have threaded into the ABS directly, but i felt this wouldnt last, so embedding a nut seemed like the best option.

Third, i carved out the hole for the L channel.  This leaves a bit of an odd shaped unsupported piece, which may be weak. Because this piece will be in the channel, i decided to leave it, as it’ll make measuring up on the built-in ruler more accurate.

Lastly, i added some pilot holes for attaching the aluminium to the 3d printed part.  i decided to use 3mm x 12mm self tapping screws for this, because i had them on hand, and they can be countersunk fairly easily.


I test-assembled the whole thing in the vice, it fitted nicely in the channel, so it was ready for connecting together.  I marked, center punched, drilled and countersunk the holes for the 3 screws that hold the whole thing together.  Add some screws and we’re sorted!


Of course, i had to do a test cut at this point, so some of the scrap acrylic pile was chopped into little strips.


Woohoo, it worked!  All it needed to be complete is some knobs.  So i headed over to thingiverse to find a knob that’ll fit nicely over an m5 nut… and found nothing useful.  No worries, i just OpenSCADdded one up.



So there it is, a useful thing i’ve made on the 3d printer that wasnt a part for a 3d printer!

 Source files (stl, openscad) are available on My GitHub 

Minimus Pin Functions v1.2

Minimus Pin Layout v1.2

Got fed up of not having the interrupt identifiers on the original minimus pinout i made, so here is version 1.1 with interrupt numbers labelled!

Stay tuned for a pinout of the Minimus 32K, as UK hackspacers have just bought over 300 of them to play with!

UPDATE: I have checked the atmega32u2 datasheet, and all pins and functions are the same as the at90usb162, so the above sheet will work for both.  Yay!

UPDATE: Oops, had the LED pins switched. fixed in v1.2

Slides from Raspberry Jam Manchester

I have been asked for th slides from the presentaion I gave at Raspberry Jam Manchester this past sunday, so here they are!

PDF Format

OpenOffice ODP Format

Original source material for the Direct Python ID section was originally posted by Matt Lloyd at http://lwk.mjhosting.co.uk/?p=343 and http://lwk.mjhosting.co.uk/?p=376.  The Slice of Pi addon boarrd is available from ciseco at http://shop.ciseco.co.uk/slice-of-pi/ for the absurdly cheap price of £3.90!

The PANIC Button

Ok, bit of explanation first.  We have an iMac set up as a ‘democratic jukebox’ at HAC:Manchester.  The idea being that anyone can put music on it, and it plays the entire library on shuffle during our hack sessions for a bit of background music.

The problem is, of course, some people have an… odd taste in music, so sometimes the jukebox ends up flipping between Aqua and Cannibal Corpse for ten minutes, and the horror of this was just too much!

Enter the PANIC button.


The button uses a minimus board. The minimus is a carrier for the AT90USB162, an AVR microcontroller with onboard USB hardware, which means it can be programmed to show up as any USB device.  Before getting the button I modified one of the pieces of LUFA demo software, a media keyboard, and stripped it down to just read the one button on the minimus.  When the button is pressed, it sends the keycode for next track. 

The button’s housing is a joke button that played an alarm and flashed when pressed, I ripped its guts out to get to the switch.  After finding the switch contacts on the original board, i soldered on two wires to connecto to the AVR.

Next,  I stripped off the USB connector  from the minimus, and added a 1m USB lead directly to the pads, to make it fit in the old speaker housing section of the button.  I connected the leads from the button to PD7 and GND on the minimus, the same as the onboard button.  This has the handy side effect that if the button is pressed while being plugged in, it boots into DFU mode, allowing me to upgrade the firmware easily.

I cut a slot in the casing for the wire to escape, and added a couple of cable ties for strain relief.

Press Button, Song Skips, Panic averted!

 [Download Code] – AVR C