STM32F072CBT6 PWM Not Working_ Here's How to Fix It

STM32F072CBT6 PWM Not Working? Here's How to Fix It

"STM32F072CBT6 PWM Not Working? Here's How to Fix It"

When working with the STM32F072CBT6 microcontroller, you may encounter situations where the Pulse Width Modulation (PWM) signal is not working as expected. This issue can be caused by several factors. Let’s break down the potential causes and walk through how to resolve it step-by-step.

Common Causes for PWM Not Working on STM32F072CBT6

Incorrect Pin Configuration One of the most common causes of PWM failure is improper configuration of the I/O pins. The STM32F072CBT6 uses specific pins for PWM output, and these pins must be configured correctly to generate the PWM signal.

Timer Misconfiguration PWM on STM32 microcontrollers is generated using timers. If the timer settings (prescaler, period, duty cycle, etc.) are not configured properly, the PWM signal will not work.

Incorrect Timer Channel Selection STM32 timers have multiple channels, and each PWM signal is tied to a specific timer channel. If the wrong channel is selected, the PWM output may fail to appear.

Clock Settings If the clock source for the timer is not properly set, the timer will not function correctly, leading to a failure in PWM generation.

PWM Pin Not Set to Alternate Function STM32 pins can be configured in different modes, such as GPIO, analog, or alternate function. If the pin is not set to the correct alternate function for PWM, it won’t output the signal.

Low or High Level in the Duty Cycle If the duty cycle is set to 0 or 100%, the PWM signal may not appear as expected. This happens because a duty cycle of 0% results in no signal, and 100% results in a continuous high signal.

How to Fix PWM Not Working

Step 1: Check Pin Configuration Make sure that you are using the correct pin for PWM output. STM32F072CBT6 supports PWM on several pins (usually marked as TIMx_CHx), and you need to configure the pin in alternate function mode.

Solution:

Open STM32CubeMX or your development environment. Select the correct pin for PWM output (e.g., PA8, PA9, etc.). Set the pin to "Alternate Function" mode and assign the corresponding timer channel (e.g., TIM1, TIM2, etc.).

Step 2: Review Timer Configuration You need to configure the timer that generates the PWM signal. The timer settings (prescaler, period, and duty cycle) must be correct.

Solution:

Configure the timer in your code, setting the prescaler and auto-reload register (ARR) values to get the desired frequency. Set the compare register (CCR) to determine the duty cycle.

Example (for Timer 1):

TIM1->PSC = 71; // Prescaler value (System clock divided by 72) TIM1->ARR = 1000; // Period TIM1->CCR1 = 500; // Duty cycle (50%)

Step 3: Verify Timer Channel Configuration Ensure the correct timer channel is selected for PWM output.

Solution:

In STM32CubeMX, configure the correct channel (e.g., TIM1 Channel 1, TIM2 Channel 2, etc.) for the PWM output. If using direct code, make sure the PWM output is connected to the right timer channel.

Step 4: Confirm Timer Clock Source The timer needs a proper clock source to function. Make sure that the timer's clock is enabled and correctly sourced from the system clock.

Solution:

Check if the clock for the timer is enabled in the RCC register (this is often done automatically in STM32CubeMX). Ensure the system clock is running correctly and that the timer’s clock is sourced appropriately.

Step 5: Set Pin to Alternate Function Mode Pins must be configured to an alternate function mode for PWM output. If the pin is set to GPIO or analog mode, it will not output a PWM signal.

Solution:

In STM32CubeMX, ensure the pin is set to "Alternate Function" mode and the appropriate alternate function (AF) is selected for the PWM signal. In code, you can manually configure the pin with HAL_GPIO_Init() and set the alternate function using the GPIO settings.

Step 6: Avoid Extreme Duty Cycles (0% or 100%) If the duty cycle is set to 0% or 100%, the PWM signal might not behave as expected. Choose a reasonable duty cycle within the range.

Solution:

Set the duty cycle to a value between 1% and 99% for visible waveform output.

Example (for 50% duty cycle):

TIM1->CCR1 = TIM1->ARR / 2; // 50% duty cycle Conclusion

To resolve the issue of PWM not working on the STM32F072CBT6, you need to ensure proper pin configuration, timer settings, and correct selection of timer channels. By following the steps above and checking each component, you should be able to fix the issue. If the PWM signal is still not working after these steps, consider using an oscilloscope or debugger to check for hardware issues such as incorrect wiring or a faulty microcontroller.