I have started working on the file system and file page. I've landed on a design with 8 pattern groups (folders) with 12 patterns in each. In addition, a yet-to-be-decided number of songs and performance setups will be available.
The external memory seems to be working OK, however, I'm not sure I'm addressing chip 1 correctly. I've moved all LCD character data to the external memory and written a separate program to load them. This saves me a lot of RAM in the main program.
Lastly, I've added a slight longer delay to each LCD write, this completely fixed problems I've had with disappearing characters and errors related to the display. I've also connected the mode-dial to the different modes, making it possible to switch between the step sequencer, setup and file pages.
For some reason, no tracks are available when I disconnect and reconnect the power. Not sure if this is related to the internal saving of pattern settings, will have to check this later.