Exercise - Using Macros

Macros are sections of code that are repeated a number of times within a program.
It is more efficient to use a macro than to create the code repeatedly every time it is needed.
For more information about macros, see What Is a Macro?.

This exercise shows how to use macros with a menu to create a simple LED flasher. The LED can be made to flash at different frequencies by pressing different switches.

The first section looks at creating the core program, with the menu. The second section shows how to create the macro.

The main sequence

This part of the program uses three switches to select the frequency for the LED.
The flowchart sequence will be:

• Read the state of the switches.
• Use this state to determine the correct branch to take.
• Set up the appropriate time delay for the chosen frequency.
• Run the macro with that delay setting.
• Loop back and check the switches again.

Linking frequency and delay

200px

The flowchart controlling the LED flashes is shown opposite.
The table that follows shows the link between length of delay in each 'Delay' icon, and the frequency of flashing. The LED is switched on for one delay period, and then off for one delay period.

LED frequency and delay
Delay in milliseconds	Frequency
1000	0.5
500	1
250	2
125	4

Create the variables

The program will use two variables, 'selection', to store the state of the switches used to select frequency, and 'delay', used to determine the frequency at which the LED flashes.

• In the 'Edit' menu, on the main toolbar, click on 'Variables...' to open the Variable Manager dialogue box.

• Hover just to the left of the 'Variables' label, and click on the down arrow that appears.
• Select 'Add new' and the 'Create a New Variable' dialogue box opens.
• Name the first new variable "selection".
• Leave the variable type as 'Byte'.
• Click on 'OK'.
• Now do the same thing again to add the second variable "delay".

Help Working With Macros and Variables

Set up the 'main' flowchart

• Open Flowcode, and set up the new flowchart as described in Creating Your First Flowchart.

Create the flowchart

• Click and drag an infinite loop, between the 'BEGIN' and 'END' icons.

Add the LCD

• Locate the 'LCD' inside the 'Outputs' toolbox in the Icons toolbar.

• Hover over the image to the left of the 'LCD' label, and click on the down-arrow that appears.

Add the switch

• Locate the 'Push Round Panel' switch in the 'Inputs' toolbox in the Icons toolbar.

• Hover over the image to the left of the switch label, and click on the down-arrow that appears.
• Click on the 'Add to system panel' option to select it.
• Click on the image of the switch on the System panel to select it and drag it to a suitable position.
• On the Panel Properties, click on the 'Unconnected' label, next to 'Connection'.

A pinout of the microcontroller appears.

• Click on the rectangle that represents the pin RA1/AN1, to connect the switch to Port A, bit 1 of the microcontroller.

Add the LED

• Locate the 'Single LED' in the 'Outputs' toolbox in the Icons toolbar.

• Hover over the image to the left of the 'Single LED' label, and click on the down-arrow that appears.
• Click on the 'Add to system panel' option to select it.
• Select the LED on the System panel and drag it to a suitable position.
• Look at the Panel Properties, the 'Connection' property shows that, by default, it is connected to Port A, bit 0.

Leave it like this.