VB.NET - Code overview

Figure 11 is a listing of the program that has been collapsed to give an overview of the various subs (in VB.NET subs used more frequently than functions, though the two are very similar)

I have grouped the 9 subs into logical groupings, to help you see the overall pattern.

Global variables

Two variables are declared (DIM'd) at the top of the program..

• State. This is the state number, and is identical to the numbers in the circles in the state diagram.
• TimerCount. Used to count off ticks of a 100mS timer to generate longer delays

Event handlers

These are the subs that respond to the various events that can occur during the life and times of the FSM.

• Form1_load. This corresponds to the Init item in the state diagram. It contains the things that are needed to initialize the FSM. In my code there is a bit of stuff required by VB.NET for housekeeping and cosmetics.
• NumericUpDown1_ValueChanged. Runs whenever the simulated temperature changes.
• TimeOut. Run whenever the countdown time (described later) hits zero
• Button1_Click. Run when the alarm reset button is clicked

Outputs

I have chosen to locate the output simulation code in separate subs. This makes it easier if you want to change how an output is simulated. The two outputs are the heater and the alarm indicator.

State transitions

I have made a single sub that handles all the state transitions. It is called with the destination state number as its argument. It switches the global state number and performs all required actions.

Timer management

My particular style of creating timeouts in VB is to use a timer control with a short interval and to count off Timer_Tick events.

• StartTiming. Called to start timing a timeout interval, with the required interval as its argument
• Timer1_Tick An event handler for the VB.NET timer that generates a 100mS timebase