# Chapter 10: The Same Thing with FreeRTOS

## Sample code

- Directory: `docs/os-on-arduino/code/10_freertos`

```bash
uv run pio run -d 10_freertos -t upload
uv run pio device monitor -b 115200
```

The real-FreeRTOS examples are in `10_freertos_real`, one environment (the build
configuration picked with `-e`) per example. Replace `integrated` with `basic`,
`preemptive`, `task_control`, `semaphore` or `queue` for the others.

```bash
uv run pio run -d 10_freertos_real -e integrated -t upload
```

## Source code

The sketch for this chapter. Click a file name to expand. The code is mirrored automatically from the manuscript repository, so what you see here is always current.

### `docs/os-on-arduino/code/10_freertos`

:::{dropdown} `src/main.cpp` — 229 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/10_freertos/src/main.cpp)

```{literalinclude} ../../../../code/10_freertos/src/main.cpp
:language: cpp
:linenos:
```

:::

:::{dropdown} `include/servo_pwm.h` — 61 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/10_freertos/include/servo_pwm.h)

```{literalinclude} ../../../../code/10_freertos/include/servo_pwm.h
:language: cpp
:linenos:
```

:::

### `docs/os-on-arduino/code/10_freertos_real`

:::{dropdown} `src/basic.cpp` — 35 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/10_freertos_real/src/basic.cpp)

```{literalinclude} ../../../../code/10_freertos_real/src/basic.cpp
:language: cpp
:linenos:
```

:::

:::{dropdown} `src/integrated.cpp` — 103 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/10_freertos_real/src/integrated.cpp)

```{literalinclude} ../../../../code/10_freertos_real/src/integrated.cpp
:language: cpp
:linenos:
```

:::

:::{dropdown} `src/preemptive.cpp` — 48 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/10_freertos_real/src/preemptive.cpp)

```{literalinclude} ../../../../code/10_freertos_real/src/preemptive.cpp
:language: cpp
:linenos:
```

:::

:::{dropdown} `src/queue.cpp` — 54 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/10_freertos_real/src/queue.cpp)

```{literalinclude} ../../../../code/10_freertos_real/src/queue.cpp
:language: cpp
:linenos:
```

:::

:::{dropdown} `src/semaphore.cpp` — 44 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/10_freertos_real/src/semaphore.cpp)

```{literalinclude} ../../../../code/10_freertos_real/src/semaphore.cpp
:language: cpp
:linenos:
```

:::

:::{dropdown} `src/task_control.cpp` — 62 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/10_freertos_real/src/task_control.cpp)

```{literalinclude} ../../../../code/10_freertos_real/src/task_control.cpp
:language: cpp
:linenos:
```

:::


## On the board

```{figure} ../_static/ch10_freertos.gif
:name: fig-ch10-freertos
:width: 100%

`10_freertos` running with the monitor open. The tasks are written against a
FreeRTOS-style API (`xTaskCreate` and so on) and run by a simple scheduler inside
`loop()`; the `[FreeRTOS Task]` task increments `Count` once a second.
```

```{figure} ../_static/ch10_freertos_real.gif
:name: fig-ch10-freertos-real
:width: 100%

The real-FreeRTOS `integrated` example, flashed with
`uv run pio run -d 10_freertos_real -e integrated -t upload` (`-e` names an environment, i.e. a
build configuration, in platformio.ini). Every 2 s it prints the FreeRTOS
tick count, the free heap and the A0 reading. With nothing connected to A0, `Pot value`
floats around 200; with a potentiometer it follows the knob (0–1023).
```

## Pitfalls

(Collected from reader questions — ask via
[GitHub Issues](https://github.com/iory/build-your-own-arduino-rtos/issues).)