Initial based on example
-O3, fix return define, clock defines
Reset LEDs to how they were
Set correct device.
Change clocks to datasheet max.
Make device read-only
Add array of first N bytes of sd card for (slightly) faster access

You have to add a MSC/src/array.c which contains the actual array.

This brings reading the first 1MB from 452 kB/s to 503 kB/s as
reported by dd.
Add errorflag to ui stuff to notify when error condition triggered
-Werror
Add md5/aes implementations, decrease first_bytes size to fit.
Encrypt reads of sector>=CRYPT_START with AES-CBS using static key
Make RO/rom-array user-configurable
Move AES options up to configuration section.
More configuration and add encryption for write operations.
Add CLEAR_ON_READ flag and code.
Set LED1 on until first read completes