Debugging STM32G071CBT6 PWM Output Not Working: Common Issues

Debugging STM32G071CBT6 PWM Output Not Working: Common Issues

When dealing with an STM32G071CBT6 PWM output not working, several common issues might be causing the failure. This article will explore possible causes, guide you through troubleshooting steps, and provide a detailed solution for resolving the problem.

Common Causes for PWM Output Failure

Incorrect Timer Configuration The STM32G071CBT6 uses timers to generate PWM signals. If the timer is not configured correctly, the PWM output will not work. This can happen due to incorrect timer settings such as the prescaler, auto-reload register (ARR), and compare register (CCR) values. Incorrect GPIO Pin Configuration PWM output requires the proper configuration of the associated GPIO pin. If the pin is not configured as an alternate function or is in an incorrect mode (e.g., input mode instead of output), the PWM signal will not be output. Clock Settings The clock source for the timer might be incorrect, or the timer may not be receiving the appropriate clock input. If the clock is not enabled or the prescaler is set improperly, the PWM signal will fail to generate. Timer Interrupts Disabled PWM generation on STM32 microcontrollers often relies on timer interrupts. If these interrupts are disabled or misconfigured, the PWM signal may not be generated or may stop unexpectedly. Peripheral Reset or Disabled The timer or GPIO peripheral might have been inadvertently disabled. This often happens during initialization or as part of a peripheral reset. Incorrect DMA or Peripheral Mapping If you are using DMA (Direct Memory Access ) with PWM, ensure that the DMA is correctly configured and properly mapped to the timer. Otherwise, the PWM signal may fail to update or trigger. Incorrect Duty Cycle or Frequency Settings If the duty cycle or frequency of the PWM is set incorrectly in the configuration, it could result in a non-functional or out-of-spec PWM signal.

Troubleshooting Steps

Step 1: Verify Timer Configuration

Double-check the timer settings in the STM32CubeMX or manually in the code. Make sure the following are set correctly: Prescaler: Adjust the prescaler to set the timer frequency. ARR (Auto-reload Register): Set the timer’s period to define the frequency. CCR (Capture/Compare Register): Set the duty cycle correctly (as a percentage of the period).

Step 2: Confirm GPIO Pin Configuration

Ensure that the GPIO pin associated with the PWM output is configured in "Alternate Function" mode. For STM32, this can be done using HAL_GPIO_Init() to configure the pin with the correct alternate function for the timer's PWM output.

Step 3: Check Clock Settings

Make sure the appropriate clocks are enabled. For the STM32G071CBT6, ensure that the system clock (HCLK) and the peripheral clocks are enabled for the timer and GPIO. You can enable the clock using __HAL_RCC_TIMx_CLK_ENABLE().

Step 4: Validate Timer Interrupts (if used)

If your PWM uses interrupts, verify that the interrupt is correctly configured and enabled. Use HAL_NVIC_EnableIRQ() to enable the interrupt for the timer if necessary.

Step 5: Reset and Enable Peripherals

Check if the timer or GPIO peripherals are inadvertently disabled or reset. You can ensure the peripherals are enabled with functions like __HAL_RCC_TIMx_CLK_ENABLE() for the timer.

Step 6: Inspect DMA Configuration (if using DMA)

If you're using DMA for PWM signal updates, ensure that the DMA is configured properly. Verify that the DMA stream/channel is correctly linked to the timer peripheral and properly initialized.

Step 7: Test with Simple Settings

To rule out complex configuration errors, start with a simple PWM setup: set a basic frequency and duty cycle on a specific timer and GPIO. This helps isolate the problem to either the hardware or software configuration.

Detailed Solution

1. Setting Up Timer for PWM Output

Timer Configuration:

TIM_HandleTypeDef htim; htim.Instance = TIM2; htim.Init.Prescaler = 7999; // Prescaler to get a desired timer frequency htim.Init.Period = 999; // Period to set PWM frequency htim.Init.ClockDivision = TIM_CLOCKDIVISION_DIV1; htim.Init.CounterMode = TIM_COUNTERMODE_UP; HAL_TIM_PWM_Init(&htim);

GPIO Configuration: c GPIO_InitTypeDef GPIO_InitStruct = {0}; __HAL_RCC_GPIOA_CLK_ENABLE(); // Enable GPIOA clock GPIO_InitStruct.Pin = GPIO_PIN_5; // Example GPIO pin for PWM GPIO_InitStruct.Mode = GPIO_MODE_AF_PP; // Alternate function push-pull GPIO_InitStruct.Pull = GPIO_NOPULL; GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_HIGH; HAL_GPIO_Init(GPIOA, &GPIO_InitStruct);

2. Enabling PWM Output on Timer Channel

Set the output compare mode to PWM and start the PWM signal. c HAL_TIM_PWM_Start(&htim, TIM_CHANNEL_1); // Start PWM on channel 1 of timer

3. Debugging PWM Output

If the PWM signal is still not output, check the signal using an oscilloscope or logic analyzer. Verify the timer’s output pins (e.g., PA5) for correct frequency and duty cycle. If the signal is not generated, confirm that all the peripheral clocks are properly enabled and that the timer is not inadvertently stopped.

4. Using STM32CubeMX for Setup

STM32CubeMX can simplify the configuration process. Use it to set up the timer, GPIO, and PWM settings automatically. Ensure to select the correct timer and PWM pin, and then generate the code for your project.

Conclusion

If the PWM output is not working on your STM32G071CBT6, the issue likely lies in the timer, GPIO pin configuration, or clock settings. By following a systematic approach—starting with the basic configuration and progressively checking each part of the system—you should be able to identify and resolve the issue. Always ensure that your timer, GPIO, and clock settings are correctly configured for PWM operation.