ElMo: hardware finishing touches

Our last session involved tidying up our power cables (with a terminal block that bolts to the lid of ElMo), the addition of an on/off switch (rather than having to disconnect the battery pack each time), and a simple menu system comprising a 128x64 pixel OLED screen and three buttons (move up the menu list, move down the menu list and select the menu item).  The screen is i2c compatible and so daisychains in with the other i2c items (the PicoBorgReverse and UltraBorg boards).  Adafruit provide an Adafruit_SSD1306 python library for sending images to the display.  The buttons (picked up in Maplin) use one GPIO pin each and are also connected to a ground pin.  Ideally we'd like to print out a proper circuit board (maybe using fritzing) and solder these items to it - but time is getting short, so we'll probably stick with the breadboard look.  We are planning to add a vibrant orange perspex lid, so we'll cut that next time, using the clear lid as a template.  And add somewhere for our mascot to sit.  And maybe some wing nuts for the ultrasonic sensors, so they are easier to swing into another position.  But hopefully that will be the final few cosmetic changes to the hardware.

There is still a lot of software to write - but we have now set up a bitbucket project to track changes - you can view it at https://bitbucket.org/elmorobogo/elmorobogo

We did have a major crisis of confidence last week - after adding the OLED screen, ElMo stopped working - the raspberry pi went into a constant reboot cycle.  Cue sleepless nights, rushed purchases of replacement hardware, etc, etc.  It turns out that our batteries were out of juice... once they were recharged, everything was good to go once again.  Lesson learned :)

And finally - we're really enjoying reading how everyone else is getting on - the other PiWars blogs are getting us excited.  Not long to go now...