In this part of the lesson, you will add a capacitive soil moisture sensor to your virtual IoT device, and read values from it.
## Virtual Hardware
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.
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.
This is an analog sensor, so uses a simulated 10-bit ADC to report a value from 1-1,023.
### Add the soil moisture sensor to CounterFit
To use a virtual soil moisture sensor, you need to add it to the CounterFit app
Add the soil moisture sensor to the CounterFit app.
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.
> ⚠️ 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).
1. Make sure the CounterFit web app is running
1. Create a soil moisture sensor:
1. In the *Create sensor* box in the *Sensors* pane, drop down the *Sensor type* box and select *Soil Moisture*.
1. Make sure the `soil-moisture-sensor` app is open in VS Code
1. Open the `app.py` file
1. Add the following code to the top of `app.py` to connect the app to CounterFit:
```python
from counterfit_connection import CounterFitConnection
CounterFitConnection.init('127.0.0.1', 5000)
```
1. Add the following code to the `app.py` file to import some required libraries:
```python
import time
from counterfit_shims_grove.adc import ADC
```
The `import time` statement imports the `time` module that will be used later in this assignment.
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.
1. Add the following code below this to create an instance of the `ADC` class:
```python
adc = ADC()
```
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.
```python
while True:
soil_moisture = adc.read(0)
print("Soil moisture:", soil_moisture)
time.sleep(10)
```
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:
* 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.
* 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*.
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.
```output
(.venv) ➜ soil-moisture-sensor $ python app.py
Soil moisture: 615
Soil moisture: 612
Soil moisture: 498
Soil moisture: 493
Soil moisture: 490
Soil Moisture: 388
```
> 💁 You can find this code in the [code/virtual-device](code/virtual-device) folder.
😀 Your soil moisture sensor program was a success!
