Скачать или смотреть Solving the No PWM Output Issue on STM32F4Discovery

Discover how to resolve the `No PWM Output` issue on your STM32F4Discovery board. Learn about initializing PWM mode correctly for flawless performance.
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This video is based on the question https://stackoverflow.com/q/65590323/ asked by the user 'unkownhihi' ( https://stackoverflow.com/u/12561596/ ) and on the answer https://stackoverflow.com/a/65684928/ provided by the user 'recep' ( https://stackoverflow.com/u/12917339/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Solving the No PWM Output Issue on STM32F4Discovery: A Step-by-Step Guide

If you're working with the STM32F4Discovery board and facing a frustrating issue of having no PWM output, you're definitely not alone. Many developers encounter this problem, especially when handling timer outputs. This guide aims to digest the challenge and provide a clear-cut solution to ensure your PWM signals function properly when programmed through STM32CubeIDE.

Understanding the Problem

You’ve generated code for setting up PWM on your STM32F4Discovery board, but when probing the output with an oscilloscope, you see nothing but a straight line. This stark line indicates that there is no alternating signal being generated, which is essentially the essence of PWM (Pulse Width Modulation). In our case, it's crucial to determine why the output remains low and how to remedy the situation.

Common Causes of No PWM Output

Pulse Value Set to Zero: When configuring the PWM, the pulse (duty cycle) must be set greater than zero; otherwise, it results in a zero output.

Timer Initialization Misconfigurations: Issues with timer clock source, master configuration, or channel setup may lead to malfunctioning PWM.

Software Interrupts Not Handled Properly: When using interrupts or DMA, ensure that they’ve been correctly implemented and initialized.

Now let’s delve into how you can resolve the no PWM output issue in your STM32 code.

Step-by-Step Solution

1. Update Your Main Function

Your main function should call the HAL_TIM_PWM_Start() function correctly. The pulse value, which determines the duty cycle, must be greater than zero. Here’s a reminder of the relevant part of your code:

[[See Video to Reveal this Text or Code Snippet]]

2. Adjust the Timer Initialization (MX_TIM2_Init)

The next important step is ensuring that the timer is configured properly. In your code, you have:

[[See Video to Reveal this Text or Code Snippet]]

You must change the Pulse value to a number greater than zero but less than your Period, which, in this case, is 100. For example, set it to 50 for a 50% duty cycle.

Here’s the modified portion of your MX_TIM2_Init function:

[[See Video to Reveal this Text or Code Snippet]]

3. Confirm Other Timer Configurations

Make sure that the entire timer setup reflects the required specifications, as incorrect configurations could lead to malfunctioning behavior. Here is the essential chronological setup of configurations that should be + 1:

Counter Mode

Period

Clock Division

Auto-Reload Preload

PWM Mode Configuration

4. Verify PWM Configuration and Start

Finally, make sure you call the right function for starting the PWM. You’ve already tried HAL_TIM_PWM_Start, which is correct for this scenario. Alternatives like HAL_TIM_PWM_Start_IT or HAL_TIM_PWM_Start_DMA can introduce complications if not configured properly with their respective handlers.

Summary

A few simple changes can convert that unwavering flat line into a pulsating PWM signal on your STM32F4Discovery board. Here’s a quick recap of what to modify:

Update Pulse value to greater than zero within your PWM configuration.

Ensure correct timer initialization and settings.

Verify that you are using the appropriate PWM start function.

Armed with these adjustments, you should now be ready to see PWM outputs performing as expected. Happy coding!