IoT-For-Beginners/4-manufacturing/lessons/4-trigger-fruit-detector/virtual-device-proximity.md

Detect proximity - Virtual IoT Hardware

In this part of the lesson, you will add a proximity sensor to your virtual IoT device, and read distance from it.

Hardware

The virtual IoT device will use a simulated distance sensor.

In a physical IoT device you would use a sensor with a laser ranging module to detect distance.

Add the distance sensor to CounterFit

To use a virtual distance sensor, you need to add one to the CounterFit app

Task - add the distance sensor to CounterFit

Add the distance sensor to the CounterFit app.

1. Open the fruit-quality-detector code in VS Code, and make sure the virtual environment is activated.

2. Install an additional Pip package to install a CounterFit shim that can talk to distance sensors by simulating the rpi-vl53l0x Pip package, a Python package that interacts with a VL53L0X time-of-flight distance sensor. Make sure you are installing this from a terminal with the virtual environment activated.

   pip install counterfit-shims-rpi-vl53l0x
   

3. Make sure the CounterFit web app is running

4. Create a distance sensor:

   1. In the Create sensor box in the Sensors pane, drop down the Sensor type box and select Distance.

   2. Leave the Units as Millimeter

   3. This sensor is an I²C sensor, so set the address to 0x29. If you used a physical VL53L0X sensor it would be hardcoded to this address.

   4. Select the Add button to create the distance sensor

   

   The distance sensor will be created and appear in the sensors list.

   

Program the distance sensor

The virtual IoT device can now be programmed to use the simulated distance sensor.

Task - program the time of flight sensor

1. Create a new file in the fruit-quality-detector project called distance-sensor.py.

   💁 An easy way to simulate multiple IoT devices is to do each in a different Python file, then run them at the same time.

2. Start a connection to CounterFit with the following code:

   from counterfit_connection import CounterFitConnection
   CounterFitConnection.init('127.0.0.1', 5000)
   

3. Add the following code below this:

   import time
   
   from counterfit_shims_rpi_vl53l0x.vl53l0x import VL53L0X
   

   This imports the sensor library shim for the VL53L0X time of flight sensor.

4. Below this, add the following code to access the sensor:

   distance_sensor = VL53L0X()
   distance_sensor.begin()
   

   This code declares a distance sensor, then starts the sensor.

5. Finally, add an infinite loop to read distances:

   while True:
       distance_sensor.wait_ready()
       print(f'Distance = {distance_sensor.get_distance()} mm')
       time.sleep(1)
   

   This code waits for a value to be ready to read from the sensor, then prints it to the console.

6. Run this code.

   💁 Don't forget this file is called distance-sensor.py! Make sure to run this via Python, not app.py.

7. You will see distance measurements appear in the console. Change the value in CounterFit to see this value change, or use random values.

   (.venv) ➜  fruit-quality-detector python distance-sensor.py 
   Distance = 37 mm
   Distance = 42 mm
   Distance = 29 mm
   

💁 You can find this code in the code-proximity/virtual-iot-device folder.

😀 Your proximity sensor program was a success!