MIDIbox

Since version mios_v1_5b MIOS has supported 4-bit mode for HD44780 compatible displays

Usually this mode isn't needed, but some displays have been internally configured for 4-bit operation and don't have all the necessary connections for full 8-bit operation or You might have some other reason to try this mode out.

To configure MIOS application to use 4-bit CLCD mode, changes need to be made to the application:

First locate
'USER_Init' section of the source files ¹⁾

Then add to its own section just below the 'USER_Init' ²⁾:

;; use a CLCD, E input of first CLCD at D.7, E of second CLCD @C.4

     ;; using the 4-bit interface:
     ;; -> connect MBHP_CORE:J15:D7-D4 of the core module to D7-D4 of the LCD
     ;; -> left MBHP_CORE:J15:D3-D0 of the core module open!
     ;; -> tie D3-D0 of the LCD to ground
     movlw   0x37 | 0x80     ; E1: D.7, 4bit interface
     movwf   MIOS_PARAMETER1
     movlw   0x24 | 0x80     ; E2: C.4, 4bit interface
     movwf   MIOS_PARAMETER2
     movlw   0x00            ; LCD type 0
     call    MIOS_LCD_TypeSet''

Then you have to Compile the modified application.

See the comments ³⁾ in the code for how to connect the display to the core. In the display side, having the datasheet for it helps a lot.

More: MIOS function reference