# Chapter 11: TinyPython — Python on a Microcontroller

## Sample code

- Directory: `docs/os-on-arduino/code/11_tiny_python`

```bash
uv run pio run -d 11_tiny_python -t upload
uv run pio device monitor -b 115200
```

## 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.

:::{dropdown} `src/main.cpp` — 262 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/11_tiny_python/src/main.cpp)

```{literalinclude} ../../../../code/11_tiny_python/src/main.cpp
:language: cpp
:linenos:
```

:::

:::{dropdown} `include/tp_config.h` — 43 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/11_tiny_python/include/tp_config.h)

```{literalinclude} ../../../../code/11_tiny_python/include/tp_config.h
:language: cpp
:linenos:
```

:::

:::{dropdown} `include/tp_env.h` — 60 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/11_tiny_python/include/tp_env.h)

```{literalinclude} ../../../../code/11_tiny_python/include/tp_env.h
:language: cpp
:linenos:
```

:::

:::{dropdown} `include/tp_eval.h` — 58 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/11_tiny_python/include/tp_eval.h)

```{literalinclude} ../../../../code/11_tiny_python/include/tp_eval.h
:language: cpp
:linenos:
```

:::

:::{dropdown} `include/tp_module.h` — 69 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/11_tiny_python/include/tp_module.h)

```{literalinclude} ../../../../code/11_tiny_python/include/tp_module.h
:language: cpp
:linenos:
```

:::

:::{dropdown} `include/tp_value.h` — 72 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/11_tiny_python/include/tp_value.h)

```{literalinclude} ../../../../code/11_tiny_python/include/tp_value.h
:language: cpp
:linenos:
```

:::

:::{dropdown} `src/tp_env.cpp` — 161 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/11_tiny_python/src/tp_env.cpp)

```{literalinclude} ../../../../code/11_tiny_python/src/tp_env.cpp
:language: cpp
:linenos:
```

:::

:::{dropdown} `src/tp_eval.cpp` — 774 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/11_tiny_python/src/tp_eval.cpp)

```{literalinclude} ../../../../code/11_tiny_python/src/tp_eval.cpp
:language: cpp
:linenos:
```

:::

:::{dropdown} `src/tp_mod_gpio.cpp` — 77 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/11_tiny_python/src/tp_mod_gpio.cpp)

```{literalinclude} ../../../../code/11_tiny_python/src/tp_mod_gpio.cpp
:language: cpp
:linenos:
```

:::

:::{dropdown} `src/tp_mod_led.cpp` — 59 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/11_tiny_python/src/tp_mod_led.cpp)

```{literalinclude} ../../../../code/11_tiny_python/src/tp_mod_led.cpp
:language: cpp
:linenos:
```

:::

:::{dropdown} `src/tp_mod_matrix.cpp` — 88 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/11_tiny_python/src/tp_mod_matrix.cpp)

```{literalinclude} ../../../../code/11_tiny_python/src/tp_mod_matrix.cpp
:language: cpp
:linenos:
```

:::

:::{dropdown} `src/tp_module.cpp` — 72 lines
:icon: code

[Open on GitHub](https://github.com/iory/learning-os-from-arduino/blob/main/docs/os-on-arduino/code/11_tiny_python/src/tp_module.cpp)

```{literalinclude} ../../../../code/11_tiny_python/src/tp_module.cpp
:language: cpp
:linenos:
```

:::


## On the board

```{figure} ../_static/ch11_repl.gif
:name: fig-ch11-repl
:width: 100%

Defining and calling a function in the REPL on the board. `fact(7)` returns 5040, and `fact(30)` stops with `RecursionError`.
```

```{figure} ../_static/ch11_led_matrix.gif
:name: fig-ch11-board
:width: 70%

`led.on()` / `led.off()` turn the L LED on and off, `matrix.fill(1)` lights all 96 LEDs of the matrix, and `matrix.clear()` turns them off. (Filmed with a webcam.)
```

## In the simulator

Without the board, the same firmware running in the {doc}`simulator <../getting-started/simulator>` looks like this.

```{figure} ../_static/sim_ch11_repl.gif
:name: fig-ch11-sim
:width: 80%

In the TinyPython REPL, `led.on()` turns L on, `matrix.fill(1)` lights the whole matrix and `led.off()` turns L off. (Recorded in the simulator.)
```

## Pitfalls

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