In this lesson, we will start by learning how to use the audio output as well as temperature and light sensors. 

Circuit Playground: Part 2

The Circuit Playground Express has a real speaker! It's not going to compete with your HiFi stereo, but it can play simple songs and tones.

![Speaker](https://content.codecademy.com/courses/learn-circuitpython/circuit-playground-part-2/speaker.jpg)

In this exercise, we will add two sound clips to the board.

To access the speaker, we will need to import the module:

```py
from adafruit_circuitplayground.express import cpx
```

In the `adafruit_circuitplayground.express` file, we can play audio using the `cpx.play_file()` function. The name of the audio file will go inside the parentheses like so:

```py
cpx.play_file("just_do_it.wav")
```

In this exercise, let's output some sound by clicking button A and button B.

Here are some sound clips from <a href="https://en.wikipedia.org/wiki/Super_Mario_Bros." target="_blank" rel="noopener noreferrer">Super Mario Bros</a>: 

| Description | Size |
--- | ---
| ► [Coin](https://content.codecademy.com/courses/learn-circuitpython/circuit-playground-part-2/coin.wav) | 42 KB
| ► [Jump](https://content.codecademy.com/courses/learn-circuitpython/circuit-playground-part-2/jump.wav) | 27 KB |
| ► [Oops](https://content.codecademy.com/courses/learn-circuitpython/circuit-playground-part-2/oops.wav) | 118 KB |
| ► [Game Over ](https://content.codecademy.com/courses/learn-circuitpython/circuit-playground-part-2/game_over.wav)| 164 KB |
    
**Note:** To preview the sound clips, right-click the links above and choose to open the link in a new tab or window.

Audio: Play File

But what happens when we have more than two sounds? Two buttons is simply not enough for the cool things that we want to do.

Well, we are in luck. Circuit Playground Express comes with multiple [capacitive touch sensors](https://en.wikipedia.org/wiki/Capacitive_sensing).

This quick-start example shows how you can read the capacitive touch sensors built into SEVEN of the Circuit Playground Express pads (pad `A0` is not a capacitive touch pad).

![Cap Touches](https://content.codecademy.com/courses/learn-circuitpython/circuit-playground-part-2/cap_touch.jpg)

Pads `A1`-`A7` can be used as capacitive devices and to access them, we can use:

- `cpx.touch_A1`
- `cpx.touch_A2`
- `cpx.touch_A3`
- `cpx.touch_A4`
- `cpx.touch_A5`
- `cpx.touch_A6`
- `cpx.touch_A7`

In this exercise, we are going to add some code to the `while` loop so that there will be a musical note for each touch sensor.

Capacitive Touch

We learned how to light up the Circuit Playground Express with its NeoPixels and utilize the A and B buttons, and the slide switch. 

But did you know the Circuit Playground Express can play sound? And it has numerous sensors?

In this lesson, we are going to dive deep into the various advanced features that come with the board:

- Audio output using sound files
- Audio output using tones
- Capacitive touches
- Light sensor
- Temperature sensor

**Note:** The latter ones require the Mu Editor.

Welcome Back

The built-in speaker is not only capable of playing sound files; it can also play basic tones with the `cpx.play_tone()` function. 

For example, the code below would play the [middle C note](https://en.wikipedia.org/wiki/C_(musical_note)) for `1.0` second:

```py
cpx.play_tone(262, 1.0)
```

The `cpx.play_tone()` requires two things:

- The frequency of the tone (Hz)
- The duration of the tone (sec)

Let's try it out.

Audio: Play Tone

Now, let's learn about some of the wonderful sensors that come with the Circuit Playground Express. 

First, the Circuit Playground can see you! Okay, not really. That would be creepy. But, it can sense light and dark, as well as colors and even your pulse!

The Light Sensor in the upper left of the board (look for the eye icon) is a phototransistor. 

![Light Sensor](https://content.codecademy.com/courses/learn-circuitpython/circuit-playground-part-2/light_sensor.jpg)

To use it as a light sensor, we can access the light value using `cpx.light`.

In this exercise, we are going try this feature out. And also, we need somewhere to display the results. This is where the serial console comes in!

The serial console receives output from the CircuitPython board and displays it so you can see it. The [Mu Editor](https://www.codecademy.com/courses/learn-circuitpython/articles/mu-editor) has a serial console built into it so we will use it in a bit.



Light Sensor

Congratulations! You have learned how to program Adafruit's Circuit Playground Express.
Here are some of the things we learned:

- Audio Output

```py
cpx.play_file("sad.wav")
```
```py
cpx.play_tone(262, 1.0)
```
- Capacitive Touches: `cpx.touch_A1`
- Temperature Sensor: `cpx.temperature`
- Light Sensor: `cpx.light`

Here is the [Circuit Playground Cheatsheet](https://github.com/adafruit/awesome-circuitpython/blob/master/cheatsheet/CircuitPython_Cheatsheet.md).

**Note:** There are actually two ways to get audio output, one is via the small built-in speaker. The other is by using alligator clips to connect a headphone or powered speaker to the `A0` pin!


Review

But wait! There's more — the Circuit Playground Express can also tell the temperature!

How, you ask? With a built-in thermistor. This little sensor is a thermally sensitive resistor, meaning its resistance changes based on temperature.

![Temperature Sensor](https://content.codecademy.com/courses/learn-circuitpython/circuit-playground-part-2/temperature_sensor.jpg)

We can access its readings in CircuitPython by using `cpx.temperature` and also using the Mu Editor.




