The home straight (time to solder on...)

The last couple of weeks have been spent positioning the project for its final sprint (before the long, long cool down of debugging and documentation correction). This means that this afternoon I sent off a hefty order to the component people to request most of the bits I will need to put together the Proof of Concept!

The first thing to finish off was the interface software, the bit running on a big computer which will allow people to configure how the ODOTS operates, download competitor card data and so on. This is now all done and partially debugged (more on it in another post).

The second thing was to transpose the hardware design to a strip-board using an atmega328p. This is the bit that gets my inner Electronic Engineer very happy, bugs can be solved with extra wires and spotted with your nose, design turns into connect-the-dots and the seemingly random (but essential) components all work their way out of the woodwork. Another advantage is that I now know how much the proof of concept will cost to make. While component costs come to £20.51 (such precision, so exciting), which is more than my original goal, I am not to worried, I have not made an enormous effort to hunt out cheap components so it is likely in another revision many pounds could come off that total.

The design has been put together in KiCad (k-eye-cad or key-cad depending on which side of the flame-war you sit) a free PCB design tool that can also do strip board designs quite well - just by putting all the back-copper traces horizontal! In the layout below Red is being used for the provided strips, while Green is being used to represent all the wires that will need to be soldered on the top side.

The layout so far - now waiting to see which connections I missed.

In the Rubik's Cube project I used protoboard, a variation on strip board where each pin hole is not connected, whereas in strip board they are connected ... in strips.

Strip board (or Veroboard)

Proto-board (or Matrix Board)

This reduces the amount of soldering required, and number of funny bits of wire on both sides of the board. Both do the same job of acting as a permanent bread board with solder.

I am fairly happy with the design as it is, it is fairly compact (if unable to tessellate nicely in the standard strip board sizes) and appears to have a minimum of random wires running large distances around other components.

The next part of the project is where some of the final hardware products will come together which means things like the power consumption, physical size and usability will move from predictions to measured quantities (or qualities).

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For those following on from my previous post, he documentation has progressed as expected, currently sitting at 40 pages of informational goodness - LaTeX really helps with long documents (no massive document redraw when you move a figure/table/sentence around!). Most of the software has now got full documentation with all of the interfaces specified. The only big things left to do are explain the hardware design (including the beautiful layout above) and some user guides. Hmmm - writing those down made me think that actually those could end up being quite large pieces of work.