STM32 on FreeRTOS

When working with STM32 and FreeRTOS, memory management and interrupt priorities are the two most critical aspects.

The Setup

Using STM32CubeMX helps, but understanding what it generates is critical. For instance, the SysTick interrupt priority.

Math behind scheduling

A basic mathematical model for task shedulability in Rate Monotonic Analysis (RMA) is given by: $U = \sum_{i=1}^{n} \frac{C_i}{T_i} \leq n(2^{1/n} - 1)$

Where $C_i$ is computation time and $T_i$ is the period constraint.

Code snippet

Here is a basic setup for an LED blink task over RTOS:

void vTaskLed(void *pvParameters) {
  for(;;) {
    HAL_GPIO_TogglePin(GPIOA, GPIO_PIN_5);
    vTaskDelay(pdMS_TO_TICKS(500));
  }
}

Remember to configure the priority grouping correctly via NVIC_SetPriorityGrouping(0);.