Don't:
- Don't use write-only registers.
- Don't nest interrupt controller chips too deeply — one
big wide interrupt controller is better.
- Don't use hardware that requires short delays between register
accesses (e.g. Zilog SCC).
- Don't put information from many different places into the same I/O
register location if the OS/drivers also have to do RMW cycles to it.
- Don't decide that no-BIOS is the way to go just because it sounds cool.
- Don't use a $2.00 chip instead of a $3.00 chip and expect the performance of a $10.00 chip.
- Don't build your first run of boards without leaving a way to debug the system.
- Don't build your first run of boards with only 1 MB of RAM on board.
- Don't send us anything without correct schematics that match what you send.
- Don't program the flash and then solder it on, leaving us with no option to reprogram it.
- Don't build just one prototype that must be shipped back and forth several times.