This example displays a variable status message for some sort of washing machine (maybe an industrial parts washer). The machine can have the following states: Idle; filling; heating; washing; emptying; rinsing and cooling.

The status display “owns” the bottom line of a 2×16 LCD, i.e. row 1. We will write the display function as a self-contained subroutine. It will be called with a number in X that indicates the current machine status, i.e. dictates which message is to be displayed. The following table defines call arguments (X values) versus action or display message:

X=0 is special in that it initializes the LCD. It should be called only once, as it will result in the screen being erased, which could interfere with the “owners” of other lines of the LCD.

We need to plan exactly what we intend to display for each state, so we can be sure our messages will fit.

0123456789012345 (ruler line)
Status: Idle
Status: Filling
Status: Heating
Status: Washing
Status: Emptying
Status: Rinsing
Status: Cooling

As luck would have it, the longest status word “Emptying” can fit together with “Status: “. Had that not been the case we would have had to think up some different words, or abbreviate or eliminate “Status: “.

One thing we must watch, though, is that some words are shorter, so we will make them all the same length by padding with spaces. That avoids one word being displayed with the remnants of a previous, longer word also showing, for example “Idling” or “Rinsing”.

We will also need a small amount of code to test the message display. To do this we use two front panel buttons on the MMi201 to count up and count down a memory variable “Status”, making sure to not go over 7 or under 0.

;Status message display example from onboard LCD documentation

;Start of test code vvvvvvvvvvvvvvvvvvvv
iUpKey     iEQU     12
iDnKey     iEQU     11

Status     mEQU     0

Start
          GoSub     StatusDisplay  ;initialize
          SetMem    Status,1

Loop
          InputK    iUpKey
          GoIfT     Up
          InputK    iDnKey
          GoIfT     Down
          GoTo      Loop

Up
          Recall    Status
          Push
          GoIfXGE   7,Loop
          IncX
          Push
          Store     Status
          GoSub     StatusDisplay
          GoTo      Loop

Down
          Recall    Status
          Push
          GoIfXLE   1,Loop
          DecX
          Push
          Store     Status
          GoSub     StatusDisplay
          GoTo      Loop
;End of test code ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^

StatusDisplay:
      Branch                       ;Test X
      Target          Status0      ;Goes here if X=0
      Target          Status1      ;Goes here if X=1
      Target          Status2      ;Goes here if X=2
      Target          Status3      ;Goes here if X=3
      Target          Status4      ;Goes here if X=4
      Target          Status5      ;Goes here if X=5
      Target          Status6      ;Goes here if X=6
      Target          Status7      ;Goes here if X=7

Status0      ;Come here to initialize the LCD. Also, display "Status: "
      OBLCD_Type      2            ;initialize the LCD
      OBLCD_SetCur    1,0
;                     ;01234567
      OBLCD_Text      "Status: "
;"Fall through" and add the word "Idle" at initialization time.

Status1      ;Come here to display Idle message
      OBLCD_SetCur    1,8
;                     ;89012345
      OBLCD_Text      "Idle      "
      Return

Status2      ;Come here to display Fill message
      OBLCD_SetCur    1,8
;                     ;89012345
      OBLCD_Text      "Filling "
      Return

Status3      ;Come here to display Heat message
      OBLCD_SetCur    1,8
;                     ;89012345
      OBLCD_Text      "Heating "
      Return

Status4      ;Come here to display Wash message
      OBLCD_SetCur    1,8
;                     ;89012345
      OBLCD_Text      "Washing "
      Return

Status5      ;Come here to display Empty message
      OBLCD_SetCur    1,8
;                     ;89012345
      OBLCD_Text      "Emptying"
      Return

Status6      ;Come here to display Rinse message
      OBLCD_SetCur    1,8
;                     ;89012345
      OBLCD_Text      "Rinsing "
      Return

Status7      ;Come here to display Cool message
      OBLCD_SetCur    1,8
;                     ;89012345
      OBLCD_Text      "Cooling "
      Return