What is the real answer because I have tried 4G and 8G cards and have not gotten a single one to work. Another user claimed that it works on version 10, I have not been able to verify this.
Dynamic C 10 does not work with the RCM3100 – it’s only for products using Rabbit 4000, 5000 and 6000 processors.
Dynamic C 9 will only work with SD cards. Cards that are 4GB or larger are SDHC cards and not supported by Dynamic C 9 or the RCM3100. 1GB SD cards will work in Dynamic C 9, and 2GB SD cards might work as well, but I haven’t been able to verify that.
GitHub has unreleased code for Dynamic C 10 that introduces support for SDHC cards, but only if you format them on the Rabbit with FAT16 partitions of 2GB or smaller. I’ve successfully used 4GB and 8GB cards on an RCM43xx with that code, and was able to read/write them from my Mac. That code should eventually ship in the 10.72C release.
If you need to use SDHC cards in Dynamic C 9, please make that request with Digi sales so they can gauge interest. It may be possible to back-port the SDHC changes from DC 10 to DC 9.