pvPortMalloc and vPortFree in FreeRTOS

Introduction

pvPortMalloc and vPortFree help you get and give back memory safely in FreeRTOS. They manage memory so your program runs smoothly without crashes.

When you need to create a new task or buffer dynamically during program run.

When you want to allocate memory for data structures like queues or stacks.

When you want to free memory that is no longer needed to avoid wasting space.

When you want to avoid memory conflicts in a multitasking environment.

When you want to use FreeRTOS's built-in memory management instead of standard C malloc/free.

Syntax

FreeRTOS

void *pvPortMalloc(size_t xSize);
void vPortFree(void *pv);

pvPortMalloc returns a pointer to a block of memory of size xSize bytes.

vPortFree frees the memory block pointed to by pv that was previously allocated by pvPortMalloc.

Examples

This allocates 100 bytes of memory and stores the pointer in buffer.

FreeRTOS

char *buffer = (char *)pvPortMalloc(100);

This frees the memory previously allocated and pointed to by buffer.

FreeRTOS

vPortFree(buffer);

Allocates memory for an array of 10 integers.

FreeRTOS

int *numbers = (int *)pvPortMalloc(10 * sizeof(int));

Sample Program

This program shows how to allocate memory for 5 integers using pvPortMalloc, fill the array, print the values, and then free the memory with vPortFree.

FreeRTOS

#include "FreeRTOS.h"
#include "task.h"
#include <stdio.h>

int main(void) {
    // Allocate memory for 5 integers
    int *data = (int *)pvPortMalloc(5 * sizeof(int));
    if (data == NULL) {
        printf("Memory allocation failed\n");
        return 1;
    }

    // Use the allocated memory
    for (int i = 0; i < 5; i++) {
        data[i] = i * 10;
    }

    // Print the values
    for (int i = 0; i < 5; i++) {
        printf("data[%d] = %d\n", i, data[i]);
    }

    // Free the memory
    vPortFree(data);

    return 0;
}

Important Notes

Always check if pvPortMalloc returns NULL, which means memory allocation failed.

Use vPortFree to avoid memory leaks by freeing memory you no longer need.

These functions are thread-safe and designed for FreeRTOS multitasking environments.

Summary

pvPortMalloc gets memory safely in FreeRTOS.

vPortFree gives back memory to avoid waste.

Use them to manage memory in multitasking programs.