Introduction
This article aims to provide thorough guidance on implementing the STM32 analog watchdog using the STM32CubeIde. First, I will explain the general concept of an analog watchdog and show you how to configure an analog watchdog step-by-step. Finally, I will introduce the stm32 analog watchdog callback function, which is triggered automatically when the analog signal is out of the defined value range.
In this article, we will closely look at the STM32 analog watchdog feature in STM32 MCUs and use STM32CubeMx software to enable this functionality. In addition, we will write some code to fully implement the STM32 analog watchdog in STM32 MCUs. I will use the Nucleo-L476 MCU board for the hardware, and for the software, I will use STM32CubeIde.
What is an analog watchdog?
Imagine a situation where you have an analog sensor that monitors the temperature of a motor. When the temperature gets extremely hot, the system has to stop the motor to prevent burnout or damage to the motor. An evident approach is periodically polling the analog data and comparing it with the reference value. And when the overheating occurs, the system will turn off the motor. However, this naive approach requires a lot of computational power because it is necessary to always sample the analog data. That is when the analog watchdog comes into the scene. Instead of constantly sampling the data, it monitors the analog signal in the background, preserving precious computation time. When an anomaly occurs - overheating in our case - it triggers specific interrupts so the microcontroller can act to prevent the failures.
Let's discuss how the analog watchdog works at a fundamental level. As shown in the figure below, we define a guarded area using higher and lower threshold values. A specific interrupt will be triggered if the analog signal's value is outside this area.
STM32 ADC Configuration
First, we need to configure the ADC to use the watchdog. Since I already have an article and video tutorial about this topic, I will skip this part and switch to the watchdog configuration. You can refer to the following link and video to configure ADCs:
STM32 ADC TUTORIAL ARTICLE LINK
STM32 ADC Watchdog Configuration
We switch to the analog watchdog configuration after enabling ADC and setting other parameters. It is straightforward in the STM32CubeIDE: enable the watchdog, define the ADC channel, and set the guarded area. Also, do not forget to enable the interrupt within NVIC settings.
STM32 Analog Watchdog Callback Function
Next, we enable the interrupt by writing the following line within the main function:
HAL_ADC_Start_IT(&hadc1);
Finally, we define the callback function, which is automatically invoked when the analog signal is out of the guarded area:
void HAL_ADC_LevelOutOfWindowCallback(ADC_HandleTypeDef* hadc)
{
printf("level out \n");
}You can print messages or use breakpoints to verify that the analog watchdog is functional.
STM32 Programming Resources
The video tutorial on the analog watchdog is available on YouTube.