Gene Apperson from Digilent gave us more background on the chipKIT network and I/O shields:
- Price of the Basic I/O Shield: I was surprised at how high our cost was on this board. I had originally thought we would be able to sell it for $25, but there is no way we could get enough margin at that price to make it worth doing. Other than the OLED display, no individual part is all that expensive, but it all adds up.
- Price of the Network Shield: Same story. I was surprised at how high our cost was. The PCB is definitely more than $3. The 32khz oscillators are surprisingly expensive as well.
- Open source project: I didn’t design this board. I assigned it to our PCB designer in Romania. There was a miscommunication, and I forgot to tell her to do the design in Eagle. So, this board was done using Altium. We’re going to post the gerbers and the Altium project as open source, but unfortunately, it won’t be as useful to the community as if it had been done in Eagle. Sorry about that, but it wasn’t intentional. I’ve been working with a guy in England who is working on recreating the design in Eagle, but he’s not done yet.
- Open source libraries: Unfortunately, the driver libraries for the Network Shield are based on Microchip Applications Library code that is not open source. The high level library code (i.e. the C++ wrappers) are open source, but of course, they call into MAL code that isn’t open source. The source code is included in the distribution, but it is under the regular Microchip license agreement. One of the biggest hurdles in doing these libraries was getting it to build under the MPIDE environment. It took some changes in the IDE to get it to work. The other big problem was working out the licensing with Microchip so that we coUld even distribute it. We have plans to develop completely open source driver libraries for the Network Shield, but there is no way we had the time or resources to do it this spring and summer. When I was originally designing the Max32, I thought of the two board set of Max32 and Network Shield as the target platform. We could have kept the cost down doing it as a single board, but there is no way it would have fit in the Mega form factor. This would also have arbitrarily raised the price who didn’t care about ethernet or USB or CAN. There are always tradeoffs. The libraries for the Basic I/O shield were written entirely by Digilent and are open source. I did the OLED display library.