Use Enumerations to Control an LED Display

This example shows how to use enumerations in a MATLAB Function block. The example shows how MATLAB Function blocks exchange enumerated data with other Simulink^® blocks.

The emldemo_led_switch model uses enumerations to represent the modes of a device that controls the colors of an LED display. The MATLAB Function block receives an enumerated input signal that represents the mode. The enumerated output signal represents the color that the LED displays.

Simulink Model

To open the model, at the command prompt, enter:

emldemo_led_switch

The model contains the blocks listed in this table.

Simulink Block	Description
Step	Provides source of the on/off signal. Outputs an initial value of 0 (off) and at 10 seconds steps up to a value of 1 (on).
Data Type Conversion from `double` to `int32`	Converts the `Step` signal of type `double` to type `int32`.
Data Type Conversion from `int32` to enumerated type `switchmode`	Converts the value of type `int32` to the enumerated type `switchmode`. The Data Type Conversion block parameters have these settings: Output minimum: `[]` Output maximum: `[]` Output data type: `Enum:switchmode`
MATLAB Function block `checkState`	Evaluates the enumerated input `state` to determine the value of the enumerated output `ledval`. `state` inherits its enumerated type `switchmode` from the Simulink step signal. `ledval` has the type `Enum:led`.
Display	Displays the value of `ledval`.

Enumeration Class Definitions

The switchmode enumeration represents the allowed modes for the input to the checkstate block.

classdef switchmode < Simulink.IntEnumType
  enumeration
    OFF(0)
    ON(1)
  end
end

The led enumeration represents the colors that the checkstate block can output.

classdef led < Simulink.IntEnumType
    enumeration
        GREEN(1),
        RED(8)
    end
end

Both enumeration classes inherit from the built-in type Simulink.IntEnumType and reside on the MATLAB^® path.

MATLAB Function Block Function

The function checkState uses enumerations to activate an LED display, based on the state of a device. It lights a green LED display to indicate the ON state. It lights a red LED display to indicate the OFF state.

function ledval = checkState(state)
%#codegen

if state == switchmode.ON
    ledval = led.GREEN;
else
    ledval = led.RED;
end

Simulation

When you simulate the model, the Display block displays the state of the LED display. If you simulate the model for less than 10 seconds, the state is off. The Display block displays RED. If you simulate the model for more than 10 seconds, the state is on. The Display block displays GREEN.

Documentation