Wednesday, September 17, 2008

Arduino Rebrain Project.

After getting an Arduino Decimila for my repstrap, Zach at RRRF developed the bigger-brained (RAM&ROM) & additionally-fingered (digital input/output) Sanguano.

Oh, and Zach has done a lot of clever work on the software side of things too.

Anyway, I assumed I could get one of these larger Atmega microcontrollers and stuff it into the Arduino so it uses all the PSU, USB etc. that are already there. This would need a new board with a header to go into the old brain's socket, and pins to carry the extra IO lines.

I use 'EasyPC' which produced the 3D. The 'old' brain is shown as a DIL package but the pins would be soldered in to project out of the bottom of the PCB. The grey square is a 44 pin surface mount version of the 644P microcontroller. The 3 sets of four pins are the extra 12 I/O.

Then it got a bit more complicated. The big hole in the board is there to clear the Decimmila's in-circuit-programming connector. Unfortunately, it is connected to different pins on the new brain, so I have added a new connector on my PCB.

Also, I am unsure of the performance of the crystal oscillator - the PCB track length between the original XTAL and up to the new brain may cause problems. I have added pads for a new XTAL and a pair of capacitors close to the '644P and a pair of vias in the tracks so they can be drilled to disconnect. This isn't shown above 'cos I only thought of it last night.

The schematic is a bit tricky to read - I don't like tags that go places that I cant find, but when I connected all the points by lines on this one it is just as tricky to trace. It was originally a quick 'n' dirty hack anyway. I also haven't put the effort into finding out how to make EasyPC schematics look good. Anyway, this is a 44 pin chip so there is a lot going on anyway.


The aim of course is to make a USB sanguano by reusing as much of what I have already got. I shouldn't really have bothered because of high parts cost in small quantities and all my time (I am better then most lawyers I have met, so that makes my hours for inventing very expensive indeed!) (I do seem to enjoy myself much more than many lawyers I have met though!!).

I could make these rebrain boards for under ten pounds if I get several tens of them. Anyone interested ?

2 comments:

dgm3333 said...

I'm just wondering if it's possible to use the Atmel
AT90USBKey board with reprap. It has a much more powerful chip than
the sanguino, more pins, more memory, native USB, and its only $5 more expensive. USB means we don't have to buy an otherwise useless cable for $20 to program it, and uploads should be much faster!!

Zach Smith said...

dgm:

we certainly plan on going to a better chip in the future. the only thing holding us back is that in order to move up the chain to something that natively supports USB, we have to switch to SMT.

since the vast majority of people are turned off by hand assembling SMT parts, we have to stick with through hole for the most part.

hopefully by next year we'll start to get our boards fully assembled, and we can really branch out into some cool stuff like super powered AVRs and such.

stay tuned!