{"id":2130,"date":"2025-04-15T06:11:53","date_gmt":"2025-04-15T06:11:53","guid":{"rendered":"https:\/\/webprojects.cloud\/wordpress\/splatco\/?post_type=spl_knowledgebase&p=2130"},"modified":"2025-06-10T10:35:16","modified_gmt":"2025-06-10T10:35:16","slug":"example-a-simple-menu-system-with-oblcd","status":"publish","type":"spl_knowledgebase","link":"https:\/\/webprojects.cloud\/wordpress\/splatco\/knowledgebase\/product-documentation\/product-documentation-onboard-peripherals\/onboard-lcd\/oblcd-programming\/oblcd-examples\/example-a-simple-menu-system-with-oblcd\/","title":{"rendered":"Example: A simple menu system with OBLCD"},"content":{"rendered":"\n

The purpose of a menu system is to allow a user to move through a range of alternatives and select one, in order to either change an operating parameter or initiate an action. Most people nowadays are familiar with the menu systems in cellular telephones. A menu system you might design for a SPLat with LCD is similar.<\/p>\n\n\n\n

The following example will assume that there are just 4 push buttons available. From top to bottom these are labeled:<\/p>\n\n\n\n

Label<\/th>Name\/function<\/th><\/tr>
<-<\/td>iLeftArrow<\/td><\/tr>
-><\/td>iRightArrow<\/td><\/tr>
Y<\/td>iAccept<\/td><\/tr>
N<\/td>iReject<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Essentially the arrow keys will be used to select and change choices, while accept and reject keys will help finalise decisions.<\/p>\n\n\n\n

The menu system will affect three memory variables:<\/p>\n\n\n\n

WashTime<\/strong>. Duration of wash cycle, in minutes<\/p>\n\n\n\n

PreWash<\/strong>. True or False, depending if a pre wash cycle is required<\/p>\n\n\n\n

HotWash<\/strong>. If true, do a hot wash cycle, otherwise do a cold cycle.<\/p>\n\n\n\n

It is absolutely essential that you plan your menu system on paper before you start writing any program code. The following table is a plan for the menu for a washing machine. It gives a choice of hot or cold wash and allows setting of the wash time between 5 and 25 minutes. Each row of the table corresponds to one display on the LCD. We will start by analyzing this tabulated plan, then we will see how it translates into SPLat code.<\/p>\n\n\n\n

 <\/th>Display<\/th><-<\/th>-><\/th>Y<\/th>N<\/th><\/tr>
0<\/td> <\/td> <\/td> <\/td>[1]<\/td> <\/td><\/tr>
1<\/td>0123456789012345<\/code>Wash type: XXXX<\/code>Change?<\/code><\/td>[3]<\/td>[2]<\/td>Hot:[5] Cold:[4]<\/td>[0]<\/td><\/tr>
2<\/td>0123456789012345<\/code>Wash time: xx<\/code>Change?<\/code><\/td>[1]<\/td>[3]<\/td>[6]<\/td>[0]<\/td><\/tr>
3<\/td>0123456789012345<\/code>Pre-wash: Xxx<\/code>Y or N to change<\/code><\/td>[2]<\/td>[1]<\/td>Xxx=Yes Save<\/td>Xxx=No Save<\/td><\/tr>
4<\/td> <\/td>[5]<\/td>[5]<\/td>Save [2]<\/td>[2]<\/td><\/tr>
5<\/td> <\/td>[4]<\/td>[4]<\/td>Save [2]<\/td>[2]<\/td><\/tr>
6<\/td>0123456789012345<\/code>Change wash time<\/code> xx<\/code><\/td>Dec xx min 5<\/td>Inc xx max 25<\/td>Save [3]<\/td>[3]<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Each row of the table is numbered. We call the numbers “State Numbers” and the whole table we call a “State Transition Table” or just “State Table”. If you are familiar with SPLatMaps or bubble diagrams you may recognize this as an alternative way of representing a Finite State Machine.<\/p>\n\n\n\n

The State table has 6 columns. One is just for the state number. The second column is for the LCD display in that state. The final 4 columns specify what happens if the user presses each of the 4 available buttons. These are the “action columns”.<\/p>\n\n\n\n

In an action column a number in [square brackets] means go to that new state (row) and change the display accordingly. The action columns can contain other actions as well, such as “Save” or change a variable (I’ve used X<\/a>‘s as placeholders for variables both in the display column and in the action columns). I’ve also included a ruler line in the displays.<\/p>\n\n\n\n

Let’s go through the 6 states, one at a time:<\/p>\n\n\n\n

State 0<\/h6>\n\n\n\n

This allows for the possibility of the LCD not always being “owned” by the menu system. Perhaps in this state the bottom line shows wash temperature. Pressing Y will take us into the menu system proper at state 1.<\/p>\n\n\n\n

State 1<\/h6>\n\n\n\n

Offers us the option to change the wash type. Pressing Y to accept the offer takes us to state 4 or 5, depending on the current wash type selection (hot or cold). Pressing an arrow key takes us to 2 or 3. If you study the arrow key actions for state 1, 2 and 3 you will discover that they form a loop, allowing you to scroll through these 3 “top level” menu choices. Pressing the N button takes us back to state 0, or notionally out of menu mode.<\/p>\n\n\n\n

State 2<\/h6>\n\n\n\n

Displays the current wash time and asks if we want to change it. If we accept (Y) we go to state 6, which allows the wash time to be changed.<\/p>\n\n\n\n

State 3<\/h6>\n\n\n\n

Lets us change the selection of the pre-wash.<\/p>\n\n\n\n

States 4 and 5<\/h6>\n\n\n\n

These work together as a pair to allow toggling between hot wash and cold wash. The arrow keys toggle between them, Y accepts the current selection by saving it and N exits back to the top level of the menu without changing the setting.<\/p>\n\n\n\n

State 6<\/h6>\n\n\n\n

Displays the wash time and allows us to change it using the arrow keys. Y saves the changed value while N rejects it. Notice that the table specifies that the value can only be incremented and decremented between the limits 5 to 25.<\/p>\n\n\n\n

A few notes on all this:<\/p>\n\n\n\n