Motion Detection

Simulation

We will be using an MP6050 which is 6-axis Motion Tracking Device which can also be called an inertial measurement unit (IMU). It has both a gyroscope and accelerometer built into it.

View the Raspberry Pi Pico on Wokwi that has been setup with an MPU6050.

You should see a Pi Pico connected to the MP6050 and 2 LEDs.

Activity

Read the code and predict what will happen when you run the simulation.
Run the simulation and click on the MP6050 to alter the pitch of the device (x-rotation).
Why do the LEDs change?
Modify the code to handle y or z rotation?
The data is being displayed in the output window of Wokwi or when you run it on your device. Change the output to display as comma separated values. Take a copy of the output and paste it into a spreadsheet to analyse the data. What do you notice?
Using the supplied mechatronics kit build the motion detection system. Test it out! Step by step instructions are below

Building the Motion Detection System

Materials

Pi Pico x1
MP6050 x1
Breadboard and jumper wires
LEDs x2
220 ohm resistors x2

Note

Red wires are power
Black wires are ground
Other coloured wires are signals

Step 1: Pico and MPU6050

Attach the Pi Pico and the MP6050 sensor to the terminal strip of the breadboard.

Step 2: LED Connection

Insert the LEDs into the breadboard. The cathode (longer leg) should be connected to a GPIO pin on the Pi Pico and the anode (shorter leg) should be connected to a resistor, which is then connected to ground. The resistors are used to limit the current flowing through the LED, which prevents it from burning out.

GPIO Pin	LED Cathode	Resistor	Ground
18	Green	220 ohm (Ω)	GND
19	Blue	220 ohm (Ω)	GND

Note

The black ground wire is connected from the Pi Pico to the -ve rail of the breadboard.
The red power wire is connected from the Pi Pico to the +ve rail of the breadboard.

Step 3: Power and Ground Connections

Connect the power and ground wires for the MP6050 sensor to the breadboard. The VCC pin should be connected to a 3.3V power source, and the GND pin should be connected to ground.

MP6050 Pin	Pi Pico Pin
VCC	3.3V Power Source
GND	Ground

Step 4: I2C/Signal Connection

Connect the I2C pins for the MP6050 sensor to the breadboard. The SCL pin should be connected to GPIO 15, and the SDA pin should be connected to GPIO 14.

MP6050 Pin	Pi Pico Pin	Colour
SCL	GPIO 15	Orange
SDA	GPIO 14	White

Step 5: Code Implementation

Open VSCode and create a new Raspberry Pi Pico project.
Copy the file mpu6050.py from the repository into your project folder.

Create a file called main.py and add the following code:

from mpu6050 import MPU6050
from machine import Pin, I2C
import time

time.sleep(0.1) # Wait for USB to become ready

errorLed = Pin(19, Pin.OUT)
okLed = Pin(18, Pin.OUT)

i2c = I2C(1, sda=Pin(14), scl=Pin(15))
mpu = MPU6050(i2c)

# wake up the MPU6050 from sleep
mpu.wake()


try:
  # continuously print the data
  while True:
      gyro = mpu.read_gyro_data()
      accel = mpu.read_accel_data()
      print("Gyro: " + str(gyro) + ", Accel: " + str(accel))

      if 20 > gyro[0] > -20:
        okLed.high()
        errorLed.low()
      else:
        okLed.low()
        errorLed.high()

      time.sleep(0.1)
except:
  pass

Step 6: Upload and Run the Code

Connect the Pi Pico to your computer via USB.
Click on the Toggle Virtual MicroPython Workspace button to open a new VSCode window with the MicroPython workspace.
Right click on the 'mpu6050.py' file and select 'Upload file to Pico'.
Check that the file has been uploaded by checking the 'Mpy Remote Workspace' folder
Select the main.py file and click run to execute the program on the Pi Pico.

Note

You will need to have followed the getting started guide to set up VSCode for Raspberry Pi Pico development.

Debugging

MPU Wake error

Check that your wiring is correct and that the code Pins match your wiring.

>>> 
Traceback (most recent call last):
  File "<stdin>", line 14, in <module>
  File "mpu6050.py", line 30, in wake
OSError: [Errno 5] EIO

>>>

SCL or SDA error

Check that your wiring is correct and that the code Pins match your wiring.
Check that you are using compatible I2C pins on the Pi Pico.

>>> 
Traceback (most recent call last):
  File "<stdin>", line 10, in <module>
ValueError: bad SCL pin

>>>