I2C based soil moisture sensor. A continuation of the Chirp - plant watering alarm project. There is also an RS485 and an analog version available.
##I2C protocol Available registers for reading and writing.
| Name | Register | R/W | Data length |
|---|---|---|---|
| GET_CAPACITANCE | 0x00 | (r) | 2 |
| SET_ADDRESS | 0x01 | (w) | 1 |
| GET_ADDRESS | 0x02 | (r) | 1 |
| MEASURE_LIGHT | 0x03 | (w) | 0 |
| GET_LIGHT | 0x04 | (r) | 2 |
| GET_TEMPERATURE | 0x05 | (r) | 2 |
| RESET | 0x06 | (w) | 0 |
| GET_VERSION | 0x07 | (r) | 1 |
###Arduino example
#include <Wire.h>
void writeI2CRegister8bit(int addr, int value) {
Wire.beginTransmission(addr);
Wire.write(value);
Wire.endTransmission();
}
unsigned int readI2CRegister16bit(int addr, int reg) {
Wire.beginTransmission(addr);
Wire.write(reg);
Wire.endTransmission();
delay(20);
Wire.requestFrom(addr, 2);
unsigned int t = Wire.read() << 8;
t = t | Wire.read();
return t;
}
void setup() {
Wire.begin();
Serial.begin(9600);
writeI2CRegister8bit(0x20, 6); //reset
}
void loop() {
Serial.print(readI2CRegister16bit(0x20, 0)); //read capacitance register
Serial.print(", ");
Serial.print(readI2CRegister16bit(0x20, 5)); //temperature register
Serial.print(", ");
writeI2CRegister8bit(0x20, 3); //request light measurement
Serial.println(readI2CRegister16bit(0x20, 4)); //read light register
}
##Address change example By default the sensor comes with 0x20 set as an address, this is an example on how to change address for indivitual sensor:
#include <Wire.h>
void writeI2CRegister8bit(int addr, int reg, int value) {
Wire.beginTransmission(addr);
Wire.write(reg);
Wire.write(value);
Wire.endTransmission();
}
void writeI2CRegister8bit(int addr, int value) {
Wire.beginTransmission(addr);
Wire.write(value);
Wire.endTransmission();
}
void setup() {
Wire.begin();
Serial.begin(9600);
//talking to the default address 0x20
writeI2CRegister8bit(0x20, 1, 0x21); //change address to 0x21
writeI2CRegister8bit(0x20, 6); //reset
delay(1000); //give it some time to boot
}
/*loop scans I2C bus and displays foud addresses*/
void loop()
{
byte error, address;
int nDevices;
Serial.println("Scanning...");
nDevices = 0;
for(address = 1; address < 127; address++ )
{
// The i2c_scanner uses the return value of
// the Write.endTransmisstion to see if
// a device did acknowledge to the address.
Wire.beginTransmission(address);
error = Wire.endTransmission();
if (error == 0)
{
Serial.print("I2C device found at address 0x");
if (address<16)
Serial.print("0");
Serial.print(address,HEX);
Serial.println(" !");
nDevices++;
}
else if (error==4)
{
Serial.print("Unknow error at address 0x");
if (address<16)
Serial.print("0");
Serial.println(address,HEX);
}
}
if (nDevices == 0)
Serial.println("No I2C devices found\n");
else
Serial.println("done\n");
delay(5000); // wait 5 seconds for next scan
}