Grove Soil Moisture Sensor
In this section, we will detail how the sensors work, how to get sensor data using Wio Terminal and how to send the data out using Wio Terminal & Grove - Wio-E5.
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Working Principle of Sensors
In this section, we will first give a short introduction to soil moisture sensors to help you to be able to understand more clearly how the sensors work.
Grove - Soil Moisture Sensor can measure soil moisture for plants. The soil moisture sensor consists of two probes that allow the current to pass through the soil and then obtain resistance values to measure soil moisture content. It can be used to decide if the plants in a garden need watering. You can also use soil moisture sensors in gardens to automate watering plants. It can be used very easily by just inserting the sensor into the soil and reading the output using ADC.
For more information on the use of soil moisture sensors its reference here.
Materials Required
 |  |  |
| Wio Terminal | Grove - Wio-E5 | Grove Soil Moisture Sensor |
Preliminary Preparation
Software preparation
Step 1. You need to Install an Arduino Software.
Step 2. Launch the Arduino application.
Step 3. Add Wio Terminal to the Arduino IDE.
Open your Arduino IDE, click on File > Preferences, and copy below url to Additional Boards Manager URLs:
https://files.seeedstudio.com/arduino/package_seeeduino_boards_index.json
Click on Tools > Board > Board Manager and Search Wio Terminal in the Boards Manager.
Step 4. Select your board and port
You'll need to select the entry in the Tools > Board menu that corresponds to your Arduino. Selecting the Wio Terminal.
Select the serial device of the Wio Terminal board from the Tools -> Port menu. This is likely to be COM3 or higher (COM1 and COM2 are usually reserved for hardware serial ports). To find out, you can disconnect your Wio Terminal board and re-open the menu; the entry that disappears should be the Arduino board. Reconnect the board and select that serial port.
For Mac User, it will be something like /dev/cu.usbmodem141401.
If you are not able to upload the sketch, mostly it's because Arduino IDE was not able to put Wio Terminal to bootloader mode. (Because MCU was halted or your program handling USB) Workaround is putting your Wio Terminal to bootloader mode manually.
Step 5. Download Grove - Wio-E5 Library
Visit the Disk91_LoRaE5 repositories and download the entire repo to your local drive.
Step 6. Adding libraries to the Arduino IDE
Now, the 3-Axis Digital Accelerometer library can be installed to the Arduino IDE. Open the Arduino IDE, and click sketch -> Include Library -> Add .ZIP Library, and choose the Disk91_LoRaE5 file that you've have just downloaded.
Get the value of the Soil Moisture Sensor
Step 1. Connecting sensors
If you want to use the soil moisture sensor, please take care to connect the soil sensor to the Grove port on the right side of the Wio Terminal and connect the Grove - Wio-E5 to the Grove port on the left side. This is different from other sensors.
The reason why the wiring method of the soil moisture sensor is different from other sensors is that it takes up an analog input interface, which the IIC interface on the left does not have, so the voltage value returned by the soil moisture sensor cannot be obtained.
Step 2. Get the moisture value from the soil moisture sensor.
This repo demonstrates how to use the soil moisture sensor. The soil moisture sensor uses an analog interface where you can simply read the moisture value of the soil by reading its pins.
int sensorPin = A0;
int sensorValue = 0;
void setup() {
Serial.begin(9600);
}
void loop() {
// read the value from the sensor:
sensorValue = analogRead(sensorPin);
Serial.print("Moisture = " );
Serial.println(sensorValue);
delay(1000);
}
Open the serial monitor of Arduino IDE and select the baud rate as 9600 and observe the result.
Send data via Grove - Wio-E5
We combine the previous code of Grove - Wio-E5 to connect to the LoRa® network. Using the AT command it is possible to send the value of the soil moisture sensor to the LoRa® network.
As we know from the code in the section above to get the soil moisture sensor value, the soil moisture value obtained is an integer data of less than eight bits.
In this way, we determine the content, size and format of the data to be sent via the AT command. We might as well set up a large enough array, store the strings we need to send into the array, and finally use the send_sync() function to send the array out.
The pseudo-code for the above idea is roughly as follows.
......
sensorValue = analogRead(sensorPin);
static uint8_t data[2] = { 0x00 }; //Use the data[] to store the values of the sensors
data_decord(sensorValue, data);
if ( lorae5.send_sync( //Sending the sensor values out
8, // LoRaWan Port
data, // data array
sizeof(data), // size of the data
false, // we are not expecting a ack
7, // Spread Factor
14 // Tx Power in dBm
)
)
.......
The rest of what we need to do is to use the begin() function to initialize Grove - Wio-E5 and the setup() function to configure the triplet information of Grove - Wio-E5. When we send a data message using the send_sync() function, we will try to join the LoRaWAN® at the same time, and once it succeeds, the data will be sent and information such as signal strength and address will be returned.
The full code example can be found here.
We do not recommend that you upload the code now to see the results, because at this point you have not yet configured Helium/TTN and will get a "Join failed" result. We recommend that you upload this code after you have completed the Connecting to Helium or Connecting to TTN chapter to complete the complete data sending process.
Once you have experienced and understood how the soil moisture sensor works and the data format, please continue with the next step of the tutorial join LoRaWAN®.
| Helium Section | |
| Helium Introduction In this chapter, we will introduce the Helium console controls that we use to get a first impression of the Helium console. Jump to chapter > |
| Connecting to Helium This section describes how to configure Helium so that sensor data can be successfully uploaded to and displayed in Helium. Jump to chapter > |
| TTN Section | |
| TTN Introduction In this chapter, we will introduce the TTN console controls that we use to get a first impression of the TTN console. Jump to chapter > |
| Connecting to TTN This section describes how to configure TTN so that sensor data can be successfully uploaded to and displayed in TTN. Jump to chapter > |
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