Code portability between RCM3700 and RCM3720

I am trying to add a 122x32 LCD to the Rabbit modules. I have hooked it up exactly like the lcd/keypad option from Rabbit to the RCM3700 proto board. The commands for this LCD (based on an Epson driver) are the same as for the Rabbit unit.

When I try to program the LCD using one of the examples (scrolling.c), I see a behavior I do not understand:

  • When using an RCM3720 on the proto board, I do not see any of the LCD data buses toggling (PA7 - PA0 on the RCM3720). The LCD screen stays completely blank. I have tried two RCM3720 modules with the exact same result.
  • When using an RCM3710 module on the same proto board, I see all the data buses toggling, but junk characters appearing on the LCD.

I do not have an RCM3700 to try. I am wondering if there is something specific in the code that makes it work only on the RCM3700, although my understanding was that the only difference between these modules is the amount of flash/SRAM. The libraries use assembly extensively. Is it possible that somehow register addressing gets messed up between these core modules? I am just surprised that the RCM3710 and the RCM3720 behave so differently.

I have been banging my head over this this past week, any help will be greatly appreciated!


I guess I should learn to read the manual carefully. It says quite clearly:
#define RCM_3700_PROTOBOARD

to use an RCM3720 on an RCM3700 proto board.

Now I just need to figure out why I am getting junk characters on the LCD.