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| − | Macros are sections of code that are repeated a number of times within a program.<br />
| + | For an excellent introduction guide, we recommend [https://www.flowcode.co.uk/education/ Introduction to microcontroller programming] |
| − | It is more efficient to use a macro than to create the code repeatedly every time it is needed.<br />
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| − | For more information about macros, see [[What Is a Macro?]]. | |
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| − | 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.
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| − | The first section looks at creating the core program, with the menu. The second section shows how to create the macro.
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| − | __TOC__
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| − | ==Linking frequency and delay==
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| − | [[File:gen_exerciseUsingMacros_LEDflash_01.png|200px|right]]
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| − | The flowchart controlling the LED flashes is shown opposite.<br />
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| − | The table that follows shows the link between length of delay in each 'Delay' icon, and the frequency of flashing.
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| − | The LED is switched on for one delay period, and then off for one delay period.
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| − | {| class="wikitable" style="text-align:center;"
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| − | ! colspan="2" | LED frequency and delay
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| − | |-
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| − | | Delay in milliseconds || Frequency
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| − | |-
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| − | | 1000 ||0.5
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| − | |-
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| − | | 500 ||1
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| − | | |
| − | |-
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| − | | 250 ||2
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| − | | |
| − | |-
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| − | | 125 ||4
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| − | |}
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| − | ==Create the variables==
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| − | 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.
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| − | :* In the 'Edit' menu, on the main toolbar, click on 'Variables...' to open the [[Variable Manager]] dialogue box.
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| − | ::* Hover just to the left of the 'Variables' label, and click on the down arrow that appears.
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| − | ::* Select 'Add new' and the 'Create a New Variable' dialogue box opens.
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| − | ::* Name the first new variable "selection".
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| − | ::* Leave the variable type as 'Byte'.
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| − | ::* Click on 'OK'.
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| − | ::* Now do the same thing again to add the second variable "delay".
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| − | ==Create the macro==
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| − | [[File:gen_exerciseUsingMacros_setfreqprop_01.png|250px|right]]
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| − | * Open the 'Macro' menu on the main toolbar, and click on the 'New...' option.
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| − | : The 'Create a New Macro' dialogue box opens.
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| − | :* Name the new macro "Set_Frequency".
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| − | :: (Notice the underscore!
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| − | :: Macro names must appear to be a single word. To use more than one word, join them together with underscore characters.)
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| − | :* Hover to the left of the 'Parameters' label, and click on the down arrow that appears.
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| − | :* Click on 'Add new' and then write in the name "delay" as the variable name in the dialogue box that opens.
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| − | :* Leave the 'Description:' box empty, and accept the default variable type, 'Byte'.
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| − | :* Click on 'OK'.
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| − | : The dialogue box for this macro is shown opposite.
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| − | : Notice that this creates a new tab, called 'Set_Frequency' on the Flowcode work area.
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| − | [[File:gen_exerciseUsingMacros_macroloop_01.png|250px|right]]
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| − | :* Click on this tab so that you can create the details of the macro.
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| − | ::* Drag and drop a 'Loop' icon between 'BEGIN' and 'END'.
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| − | ::* Double click on it to open its dialogue box.
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| − | ::* Change the 'Display name:' to "Loop ten times".
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| − | ::* Click on 'OK'.
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| − | ::* Tick the 'Loop count:' box and insert the number "10".
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| − | [[File:gen_exerciseUsingMacros_outprop_01.png|250px|right]]
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| − | : The dialogue box for the 'Loop' is shown opposite.
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| − | ::: Inside the loop:
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| − | ::* Drag and drop and 'Output' icon, and double click on it.
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| − | :::* Change the 'Display name:' to "Switch on".
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| − | :::* Configure it to output value "1" to bit 0 of Port A.
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| − | :::* Click on 'OK'.
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| − | [[File:gen_exerciseUsingMacros_macrodelay_01.png|250px|right]]
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| − | : This dialogue box for the 'Output' icon is shown opposite.
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| − | ::* Follow this icon with a 'Delay' icon, and double click on it.
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| − | :::* Leave the 'Display name:' as 'Delay', and the timing units as 'milliseconds'.
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| − | :::* In the 'Delay value or variable:' box, type the name of the variable "delay".
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| − | :::* Click on 'OK'.
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| − | : The dialogue box for this 'Delay' is shown opposite.
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| − | ::* Next, place a second 'Output' icon.
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| − | ::: The easiest way to do this is to 'copy and paste' the first one, then select the copy and drag it into position.
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| − | ::* Double click on it and rename it "Switch off".
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| − | :::* Configure it to output value "0" to bit 0 of Port A.
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| − | :::* Click on 'OK'.
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| − | ::* Follow that with a second 'Delay' icon, configured in exactly the same way as the first.
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| − | ::: (Again, 'copy and paste' followed by dragging the resulting icon is the easiest way to do this.)
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| − | : The structure of the macro should resemble that shown below.
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| − | [[File:gen_exerciseUsingMacros_macroprog_01.png|200px|center]]
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| − | ==The main sequence==
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| − | This part of the program uses three switches to select the frequency for the LED.<br />
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| − | The flowchart sequence will be:
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| − | ::::* Read the state of the switches.
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| − | ::::* Use this state to determine the correct branch to take.
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| − | ::::* Set up the appropriate time delay for the chosen frequency.
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| − | ::::* Run the macro with that delay setting.
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| − | ::::* Loop back and check the switches again.
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| − | ==Set up the 'main' flowchart==
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| − | * Open Flowcode, and set up the new flowchart as described in [[Exercise - Creating Your First Flowchart|Creating Your First Flowchart]].
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| − | * Click and drag an infinite loop, [[File:Btn Loop.gif|30px]] between the 'BEGIN' and 'END' icons.
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| − | : Inside the loop:
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| − | [[File:gen_exerciseUsingMacros_inputprop_01.png|250px|right]]
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| − | :* Click and drag an 'Input' icon [[File:Btn Input.gif|30px]].
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| − | ::* Double click on it to open the dialogue box.
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| − | ::* Rename it "Read the switches" and set it up to input from the entire Port B.
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| − | ::* In the 'Variable:' box, type "selection"
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| − | ::: The three switches will be connected to bits 0, 1 and 2 of Port B.
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| − | ::: The state of these switches will be stored in the variable 'selection'.
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| − | ::* Click on 'OK'.
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| − | :: The input dialogue box for the 'Input' icon is shown opposite.
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| − | [[File:gen_exerciseUsingMacros_switchprop_01.png|250px|right]]
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| − | :* Click and drag a 'Switch-case' icon, [[File:Btn Switch.gif|30px]] after the 'Input' icon.
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| − | ::* Double click on it to open the dialogue box.
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| − | ::* Leave the 'Display name:' as 'Switch'.
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| − | ::* In the 'Switch:' box, type the name of the variable that will trigger the branching, "selection".
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| − | ::* Tick the first three 'Case:' boxes, and change the content of the third one from '3' to '4'.
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| − | ::* Click on 'OK'.
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| − | :: The 'Switch-case' dialogue box is shown opposite.
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| − | :* Inside each of the three branches ('=1', '=2' and '=3'), click and drag a macro icon, [[File:Btn Macro.gif|30px]] and a calculation icon, [[File:Btn Calculation.gif|30px]].
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| − | ::* In the '=1' branch, double click on the 'Calculation' icon, and rename it "One hertz delay".
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| − | ::* In the 'Calculations:' box, type "delay = 500".
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| − | ::* In the '=2' branch, double click on the 'Calculation' icon, and rename it "Two hertz delay".
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| − | ::* In the 'Calculations:' box, type "delay = 250".
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| − | ::* In the '=4' branch, double click on the 'Calculation' icon, and rename it "Four hertz delay".
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| − | ::* In the 'Calculations:' box, type "delay = 125".
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| − | The three 'Calculation' dialogue boxes are shown below.
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| − | <Gallery widths=120px>
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| − | File:gen_exerciseUsingMacros_delay1_01.png
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| − | File:gen_exerciseUsingMacros_delay2_01.png
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| − | File:gen_exerciseUsingMacros_delay4_01.png
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| − | </gallery>
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| − | ==Add the switch==
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| − | * Locate the 'Push Round Panel' switch in the 'Inputs' toolbox in the [[Tools and Views#1) Icons Toolbar|Icons toolbar]].
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| − | :* Hover over the image to the left of the switch label, and click on the down-arrow that appears.
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| − | :* Click on the 'Add to system panel' option to select it.
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| − | :* Click on the image of the switch on the System panel to select it and drag it to a suitable position.
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| − | :* On the Panel Properties, click on the 'Unconnected' label, next to 'Connection'.
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| − | :: A pinout of the microcontroller appears.
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| − | :* Click on the rectangle that represents the pin RA1/AN1, to connect the switch to Port A, bit 1 of the microcontroller.
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| − | ==Add the LED==
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| − | * Locate the 'Single LED' in the 'Outputs' toolbox in the [[Tools and Views#1) Icons Toolbar|Icons toolbar]].
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| − | :* Hover over the image to the left of the 'Single LED' label, and click on the down-arrow that appears.
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| − | :* Click on the 'Add to system panel' option to select it.
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| − | :* Select the LED on the System panel and drag it to a suitable position.
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| − | :* Look at the Panel Properties, the 'Connection' property shows that, by default, it is connected to Port A, bit 0.
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| − | :: Leave it like this.
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| − | ==The alternative==
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| − | The final flowchart is much more compact because it uses a macro. Without that, the flowchart would look like:
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| − | [[File:gen_exerciseUsingMacros_altprog_01.png|1000px|center]]
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