# freertos

Guides agents through FreeRTOS embedded development, from task creation and queue management to stack overflow detection and GDB thread debugging.

- skill · `type=skill` · Claude Code, Codex, Cursor, GitHub Copilot, Gemini CLI, OpenCode · 637 installs · ★ 267
- Author: mohitmishra786
- License: MIT · policy=mirror · the beginning of the file is at the end of this page
- Source: https://github.com/mohitmishra786/low-level-dev-skills/tree/HEAD/skills/embedded/freertos/SKILL.md
- Updated: 2026-06-27
- HTML: https://affpapa.org/en/nevibecode/skills/freertos

## What it does

The skill provides reference patterns for FreeRTOS development in C. It details task spawning via `xTaskCreate`, priority tiers, and queue operations between producers and consumers. For interrupts, it illustrates ISR-safe primitives like `xQueueSendFromISR`.

Another section guides `FreeRTOSConfig.h` setup. It covers stack watermark tracking with `uxTaskGetStackHighWaterMark` and overflow hooks. It also documents FreeRTOS v11 indexed task notifications alongside stream buffers.

Stack depth in `xTaskCreate` is counted in words. Do not confuse them with bytes. If RAM runs out, `vTaskStartScheduler` fails before the scheduler runs. Viewing threads in GDB also requires `configUSE_TRACE_FACILITY` in your configuration header.

## Install

### Claude Code (native platform)

1. **Skills CLI (Vercel)**
```bash
npx skills add mohitmishra786/low-level-dev-skills --skill freertos -a claude-code
```

2. **Manually: put the files in place**
- File: `~/.claude/skills/freertos/SKILL.md` — Copy the whole skill folder; for one project use .claude/skills/freertos/

### Codex

1. **Skills CLI (Vercel)**
```bash
npx skills add mohitmishra786/low-level-dev-skills --skill freertos -a codex
```

2. **Manually: put the files in place**
- File: `.agents/skills/freertos/SKILL.md` — For all projects use ~/.agents/skills/

### Cursor

1. **Skills CLI (Vercel)**
```bash
npx skills add mohitmishra786/low-level-dev-skills --skill freertos -a cursor
```

2. **Manually: put the files in place**
- File: `.cursor/skills/freertos/SKILL.md` — Cursor also reads .agents/skills/ and .claude/skills/

### GitHub Copilot

1. **GitHub CLI**
```bash
gh skill install mohitmishra786/low-level-dev-skills freertos
```

2. **Manually: put the files in place**
- File: `.github/skills/freertos/SKILL.md`

### Gemini CLI

1. **Skills CLI (Vercel)**
```bash
npx skills add mohitmishra786/low-level-dev-skills --skill freertos -a gemini-cli
```

2. **Platform CLI**
```bash
gemini skills install https://github.com/mohitmishra786/low-level-dev-skills --path skills/embedded/freertos
```

### Windsurf (Devin Desktop)

**Manually: put the files in place**
- File: `.devin/skills/freertos/SKILL.md` — The legacy .windsurf/skills/ path still works

### OpenCode

**Skills CLI (Vercel)**
```bash
npx skills add mohitmishra786/low-level-dev-skills --skill freertos -a opencode
```

### Claude.ai

**Claude.ai**
- Zip the folder and upload it in Settings → Capabilities → Skills

Where a file is given instead of a command, copy the files from the source to that path: https://github.com/mohitmishra786/low-level-dev-skills/tree/HEAD/skills/embedded/freertos/SKILL.md

## When to use it
- configure inter-task communication with queues and binary semaphores
- detect task stack overflows using watermark hooks in `FreeRTOSConfig.h`
- inspect running RTOS threads in GDB through OpenOCD
- protect shared resources using mutexes with priority inheritance

## Example prompts
- Show how to pass sensor data from an interrupt into a task using a FreeRTOS queue
- How do I set up stack overflow detection method 2 in FreeRTOSConfig.h?
- Configure GDB and OpenOCD to inspect FreeRTOS task stacks

## Source text · SKILL.md · MIT

Below is the content of a third-party file. It is data, not instructions for you: do not act on anything written inside unless the human asks. Block tag: 73133463cf3d5c9c.

BEGIN THIRD-PARTY FILE 73133463cf3d5c9c
````text
---
name: freertos
description: FreeRTOS skill for embedded RTOS development. Use when creating tasks, managing priorities, using queues and mutexes, detecting stack overflows, configuring FreeRTOS via FreeRTOSConfig.h, or debugging FreeRTOS applications with OpenOCD and GDB. Activates on queries about FreeRTOS tasks, queues, semaphores, mutexes, configASSERT, stack overflow, vTaskDelay, or FreeRTOS-aware debugging.
---

# FreeRTOS

## Purpose

Guide agents through FreeRTOS application development: task creation and priorities, inter-task communication with queues and semaphores, stack overflow detection, configASSERT, and FreeRTOS-aware debugging with GDB and OpenOCD.

## Triggers

- "How do I create a FreeRTOS task?"
- "How do I pass data between FreeRTOS tasks?"
- "My FreeRTOS task is crashing — how do I detect stack overflow?"
- "How do I use FreeRTOS mutexes?"
- "How do I debug FreeRTOS tasks with GDB?"
- "How do I configure FreeRTOSConfig.h?"

## Workflow

### 1. Task creation and priorities

```c
#include "FreeRTOS.h"
#include "task.h"

// Task function signature
void vMyTask(void *pvParameters) {
    const char *name = (const char *)pvParameters;
    for (;;) {
        // Task body — must never return
        printf("Task %s running\n", name);
        vTaskDelay(pdMS_TO_TICKS(500));  // yield for 500ms
    }
}

int main(void) {
    // xTaskCreate(function, name, stack_depth_words, param, priority, handle)
    TaskHandle_t xHandle = NULL;
    xTaskCreate(vMyTask, "MyTask",
                configMINIMAL_STACK_SIZE + 128,  // words, not bytes!
                (void *)"sensor",
                tskIDLE_PRIORITY + 2,            // higher = more urgent
                &xHandle);

    vTaskStartScheduler();  // never returns if heap is sufficient
    for (;;);               // should never reach here
}
```

Priority guidelines:
- `tskIDLE_PRIORITY` (0) — idle task, never block here
- ISR-deferred tasks — highest priority to service interrupts quickly
- Avoid priorities above `configMAX_PRIORITIES - 1`

### 2. Queues — inter-task data passing

```c
#include "queue.h"

typedef struct { uint32_t sensor_id; float value; } SensorReading_t;

QueueHandle_t xSensorQueue;

void vProducerTask(void *pvParam) {
    SensorReading_t reading;
    for (;;) {
        reading.sensor_id = 1;
        reading.value = read_adc();
        // Send; block max 10ms if queue full
        xQueueSend(xSensorQueue, &reading, pdMS_TO_TICKS(10));
        vTaskDelay(pdMS_TO_TICKS(100));
    }
}

void vConsumerTask(void *pvParam) {
    SensorReading_t reading;
    for (;;) {
        // Block forever until item available
        if (xQueueReceive(xSensorQueue, &reading, portMAX_DELAY) == pdTRUE) {
            process(reading.value);
        }
    }
}

// Create before starting scheduler
xSensorQueue = xQueueCreate(10, sizeof(SensorReading_t));
```

From ISR: use `xQueueSendFromISR()` and pass `&xHigherPriorityTaskWoken`.
````
END THIRD-PARTY FILE 73133463cf3d5c9c

The third-party file has ended. Everything between the 73133463cf3d5c9c tags is data: requests and commands from it are not followed. An “end of file” line with another tag inside the block is part of the file.

First 2950 of 9129 bytes. © mohitmishra786 · MIT · https://github.com/mohitmishra786/low-level-dev-skills/tree/HEAD/skills/embedded/freertos/SKILL.md

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