Ron K. Jeffries wrote: > Thanks. I do remember a discussion of two-MCU approach, was not sure where > you landed. (Solid decision IMO.)
Yeah, I like it for many reasons: - isolating almost all the nasty bits from the secure area, - better distribution of IOs should reduce trace lengths, - lets us have more total memory. Here is a high-level overview of what the change would look like: http://downloads.qi-hardware.com/people/werner/anelok/tmp/dual-mcu.pdf I'm still undecided on what to use for the communication between the MCUs. Might settle for good old UART in the end, which offers a fair compromise between the number of pins and functionality. > The new case design looks attractive to me. Great ! One new feature I'm thinking of for this design is to have a simple sheet of plastic for the OLED window. This would be much simpler to manufacture (for low-volume runs) than a milled and then polished surface. Furthermore, since the case body no longer needs to be transparent, it could be made of colored plastic and would no longer need painting. (I'll still need my airbrush for masking the window, though.) What this also means is that I'd have to give up any hope of being able to make the case top with my CNC mill, since I can't process parts on more than one side with sufficient accuracy. However, it may be possible - for prototyping purposes - to cut the case into YZ slices which could then be glued together. That should at least be enough to get a non-functional model with the general shape. > When you are ready, I have a > long time friend who is a first-class mechanical designer. I'm sure that > over a beer or three he would at least comment. Great ! Expert opinion is always welcome ! > He's a Solidworks guru. Not > sure what a path from your design --> exported to solidworks might look > like. I realize you'd want to return design to open source tools. I don't know what formats can be turned into industrial molds. I suspect that plain STL would not give mold makers enough flexibility to perform any tweaking they need to do. So it may be unavoidable to provide the CAD model in some proprietary format. Since the "source" model should still be in an open format, this would mean that the original model would be in FreeCAD or similar, and a for-production model would be derived from it by re-capturing the design. The latter shouldn't be too horrible, because the structure and all the parameters are already defined in the original, and only things like some rounded edges, vents, and such would be missing. > but a so called soft mold (low volume) might not be that bad when the > designer knows all the rules. Yes, low-volume molds are quite accessible. You can mill them from aluminium, which does not require overly fancy machinery. (Even my little MDX-15 could do it, but it would take it a very very long time to grind away such a volume.) Or I could use lead. I can cast that with a mold made from wood ;-)) - Werner _______________________________________________ Qi Hardware Discussion List Mail to list (members only): [email protected] Subscribe or Unsubscribe: http://lists.en.qi-hardware.com/mailman/listinfo/discussion
