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110 lines
4.3 KiB
110 lines
4.3 KiB
# Measure soil moisture - Virtual IoT Hardware
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In this part of the lesson, you will add a capacitive soil moisture sensor to your virtual IoT device, and read values from it.
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## Virtual Hardware
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The virtual IoT device will use a simulated Grove capacitive soil moisture sensor. This keeps this lab the same as using a Raspberry Pi with a physical Grove capacitive soil moisture sensor.
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In a physical IoT device, the soil moisture sensor would be a capacitive sensor that measures soil moisture by detecting the capacitance of the soil, a property than changes as the soil moisture changes. As the soil moisture increases, the voltage decreases.
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This is an analog sensor, so uses a simulated 10-bit ADC to report a value from 1-1,023.
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### Add the soil moisture sensor to CounterFit
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To use a virtual soil moisture sensor, you need to add it to the CounterFit app
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#### Task - dd the soil moisture sensor to CounterFit
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Add the soil moisture sensor to the CounterFit app.
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1. Create a new Python app on your computer in a folder called `soil-moisture-sensor` with a single file called `app.py` and a Python virtual environment, and add the CounterFit pip packages.
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> ⚠️ You can refer to [the instructions for creating and setting up a CounterFit Python project in lesson 1 if needed](../../../1-getting-started/lessons/1-introduction-to-iot/virtual-device.md).
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1. Make sure the CounterFit web app is running
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1. Create a soil moisture sensor:
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1. In the *Create sensor* box in the *Sensors* pane, drop down the *Sensor type* box and select *Soil Moisture*.
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1. Leave the *Units* set to *NoUnits*
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1. Ensure the *Pin* is set to *0*
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1. Select the **Add** button to create the humidity sensor on Pin 0
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The soil moisture sensor will be created and appear in the sensors list.
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## Program the soil moisture sensor app
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The soil moisture sensor app can now be programmed using the CounterFit sensors.
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### Task - program the soil moisture sensor app
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Program the soil moisture sensor app.
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1. Make sure the `soil-moisture-sensor` app is open in VS Code
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1. Open the `app.py` file
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1. Add the following code to the top of `app.py` to connect the app to CounterFit:
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```python
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from counterfit_connection import CounterFitConnection
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CounterFitConnection.init('127.0.0.1', 5000)
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```
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1. Add the following code to the `app.py` file to import some required libraries:
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```python
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import time
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from counterfit_shims_grove.adc import ADC
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```
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The `import time` statement imports the `time` module that will be used later in this assignment.
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The `from counterfit_shims_grove.adc import ADC` statement imports the `ADC` class to interact with a virtual analog to digital converter that can connect to a CounterFit sensor.
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1. Add the following code below this to create an instance of the `ADC` class:
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```python
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adc = ADC()
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```
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1. Add an infinite loop that reads from this ADC on pin 0 and write the result to the console. This loop can then sleep for 10 seconds between reads.
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```python
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while True:
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soil_moisture = adc.read(0)
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print("Soil moisture:", soil_moisture)
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time.sleep(10)
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```
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1. From the CounterFit app, change the value of the soil moisture sensor that will be read by the app. You can do this in one of two ways:
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* Enter a number in the *Value* box for the soil moisture sensor, then select the **Set** button. The number you enter will be the value returned by the sensor.
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* Check the *Random* checkbox, and enter a *Min* and *Max* value, then select the **Set** button. Every time the sensor reads a value, it will read a random number between *Min* and *Max*.
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1. Run the Python app. You will see the soil moisture measurements written to the console. Change the *Value* or the *Random* settings to see the value change.
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```output
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(.venv) ➜ soil-moisture-sensor $ python app.py
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Soil moisture: 615
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Soil moisture: 612
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Soil moisture: 498
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Soil moisture: 493
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Soil moisture: 490
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Soil Moisture: 388
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```
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> 💁 You can find this code in the [code/virtual-device](code/virtual-device) folder.
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😀 Your soil moisture sensor program was a success!
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