PWM Output

Generate square wave on the specified output pin

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Add-On Required: This feature requires the Simulink Coder Support Package for NXP FRDM-KL25Z Board add-on.

  • PWM Output block

Libraries:
Simulink Coder Support Package for NXP FRDM-KL25Z Board/FRDM-KL25Z

Description

The PWM Output block generates square-wave pulses and outputs to the specified pin on the board. You can provide a value between 0–100 as the block input. The input value that you provide controls the duty cycle of the pulse waveform. An input value of 0 produces a 0% duty cycle and an input value of 100 produces a 100% duty cycle.

Ports

Input

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The range of valid input values is 0 to 100. The input controls the duty cycle (width of the square wave) of the square waveform.

An input value of 0 produces a 0% duty cycle and an input value of 100 produces a 100% duty cycle. Any out-of-range values, such as 500 or -500, at the block input port has the same effect as the maximum or minimum input values.

Data Types: single | double | int8 | int16 | int32 | uint8 | uint16 | uint32 | Boolean

Parameters

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To view the pin mapping on the board, click View Pin Map. On the board, each PWM pin is connected to either of the three timers, TPM0 (Timer PWM Module), TPM1, or TPM2. To learn about the Timer Channel Pin combination, see the Timer to Pin Mapping table in the Timer/PWM module parameter description section.

The board has three timers, TPM0, TPM1, and TPM2. Each PWM pin is connected to one of these three timers. When you select a pin in the Pin list, this parameter is populated with the timer to which the pin is connected. For example, if you select the PTA1 (D0) pin, this parameter is set to TPM2.

The following table shows timer to pin mapping.

In your model, if you have more than one instance of the PWM Output block, use a different Timer Channel combination for every block instance. Otherwise, you receive an error message indicating you to use GPIO Pins from different Timer Channel combination for all the block instances.

For example, suppose that in one PWM Output block instance you select the PTC3 pin to generate the output. The PTC3 pin is connected to the CH2 channel of the TPM0 timer. When selecting a pin for the other instances of the PWM Output block, select a pin that belongs to a timer channel combination other than TPM0 CH2.

Dependencies

This parameter appears dimmed.

When initializing, the block sets its duty cycle to the value that you specify in this parameter.

Example

This example shows how to use the PWM Output block to control the brightness of the blue LED connected to the D13 pin on the board.

  1. Connect the FRDM-KL25Z hardware to your computer.

  2. In the Simulink® Editor, open a new model window. From the Library Browser, copy a Constant block and a PWM Output block and connect them.

  3. Set the value of the Constant block to 50. This value represents the duty cycle of the output square wave in percentage.

  4. In the Block Parameter dialog box, set the Pin to D13 and the Initial duty cycle to 0.

  5. In the Simulink Editor, select Simulation > Model Configuration Parameters.

  6. In the Configuration Parameters dialog box, click Hardware Implementation.

  7. Set the Hardware board parameter to NXP FRDM-KL25Z.

  8. To set the frequency of the output signal, identify the timer to which the D13 pin is connected.

    To identify the timer, in the Block Parameter dialog box, click View Pin Map. In the pin map, search for the D13 pin and the timer name next to it. The D13 pin is connected to the TMP0 pin.

  9. In the Configuration Parameters dialog box, set the TPM0 Frequency (in Hz) to 50. Using the frequency value, the block calculates the period of the square wave.

    Period = 1/50 = 0.02 seconds

When you build the model and load it on the hardware, the PWM Output block generates square-wave pulses with the pulse width of (50* 0.02)/100 = 0.01 seconds. The blue LED turns on for 0.01 seconds, and then it turns off for the next 0.01 seconds. You can blink an LED on and off quickly to control its brightness with the PWM Output block.

Version History

Introduced in R2016b

See Also

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