SPIKE ‘Simon Says’ game with tin foil touch sensors

Did you know that the LMS-ESP32 board features up to ten touch inputs? These inputs utilize capacitive touch sensors capable of detecting variations in electrical charge, such as those induced by human skin contact. This means they can sense when someone touches the pins with a finger. This article will show you how to build a “Simon Says” game using these touch sensors.

Before we go into the details of building and programming a Simon Says memory game with LEGO SPIKE Prime, here’s a video of the end result. We show a SPIKE Prime hub, but you can also use the teal LEGO MINDSTORMS Robot Inventor hub. It is nearly identical.

Crafting a tin foil LEGO touch sensor

1. Cut a strip of aluminum foil approximately 1cm wide and 5cm long to create a touch button. Next, wrap it around a 3M LEGO Technic beam.
2. Attach a male pin from a female/male DuPont jumper wire between the foil and another 3-beam connected with two pins to the foil-wrapped beam. Ensure one side can “click,” leaving some space on the other side for the DuPont pin.
3. Repeat this process for yellow, green, and red colors.

4. Connect the female side of the DuPont cables to GPIO ports 12 (yellow), 13 (green), 14 (blue), and 15 (red), and attach the foil sensors to the four corners of your Spike PRIME hub.

Program the LMS-ESP32 to read the tin foil touch sensors

• Flash your LMS-ESP with the ‘MicroPython v1.20 with ioty+ulab+lvgl 9.0+uartremote+pupremote’ firmware available on our online firmware installer. This firmware comes with PUPRemote and LPF2 preinstalled.
• Upload the simon_esp32.py to your LMS-ESP32 board. Rename it to “main.py”, so it starts automatically on boot. You can use Thonny to do that.

Program the Spike PRIME using PyBricks

• Upload the PUPRemote library into your PyBricks environment. To do so, follow Step 3 in our tutorial about connecting gamepads and neopixels.
• Import the program simon_pybricks.py.

Start playing Simon Says on your SPIKE Prime or Robot Inventor hub

When you start the PyBricks program, the pixel next to the green touch sensor blinks. By touching the green button, a new game is started. Wait for a new sequence to finish and try to reproduce this exact sequence. Once you fail to reproduce, you will hear the fail tune, and the level you reached is shown. The tens are shown as 4 pixels in the corners, and the ones by a single pixel near the blue button.

How do the programs work?

LMS-ESP32
The touch pins can easily be read with the following code snippet:

from machine import TouchPad, Pin
touch_pins = [TouchPad(Pin(i, mode=Pin.IN)) for i in [0,2,4,12,13,14,15,27,32,33]]
pin = 3
val = touch_pins[pin].read()

The value read from a touch pin is typically 800 when not touched and decreases to 300 or 400 when touched. This level depends on whether the external USB power is connected to the LMS-ESP32. Without USB power, the value tends to be a little higher. So, for a safe threshold, we use the value of 450.

Using the PUPRemote library, we define three functions that can be called from the Lego brick:

p=PUPRemoteSensor(sensor_id=SPIKE_ULTRASONIC)
p.add_command('touch','H')
p.add_command('val','4H')
p.add_command('tresh','H','H')

• touch reads all touch sensors and returns a single value with a bit representation of the individual touch pins,
• val returns the value of the touch sensors on pins 12, 13, 14, and 15,
• tresh allows to change the threshold value.

Now that we have the touch sensors enabled in the LMS-ESP32, we can read them from the PyBricks side using the PUPRemote call:

PyBricks

btns = p.call('touch')

In the btns value every touch pin represents a specific bit. So, when, e.g., GPIO12 is touched, the return value would be 2**3 = 8. For the colors in our example, the values are yellow:8, green:16, blue:32, and red: 64.

Troubleshooting Simon Says and tin foil touch sensors

Upload the touch_pybricks.py program to the PyBricks environment. This test program will show which button is pressed and print the touch sensors’ raw values. Furthermore, a pixel next to the pressed button will light up. Notice that the communication is rather slow because our emulated sensor has to switch between two modes (one for reading the buttons, the other for reading the touch values).

['.', 'g', '.', '.']
 559, 363, 570, 516
['.', '.', 'b', '.']
 559, 529, 366, 511

If the buttons do not seem to work, check the lower values of the touch sensor and adjust the threshold in the line:

p.call('tresh',400)

This value should be larger than any of the smaller numbers you see in the output. Eventually, you can use that threshold value in your simon_pybricks.py program.

What’s next after building this Simon Says game with touch sensors

Here are some ideas for expanding after you build it.

1. Play the game and invite friends to play it, too. What is your high score?
2. Customize the game by adding new levels. Can you make it go faster? Is it fun with an extra color? Can you the game keep a score?
3. Can you improve the model so that it looks better, more integrated, and more solid?

I’m looking forward to seeing your video and pictures. Be sure to drop us a line on Facebook, Instagram, YouTube, or TikTok.