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 # i2c-moisture-sensor
-I2C based soil moisture sensor
+
+I2C based soil moisture sensor. A continuation of the [Chirp - plant watering alarm](https://github.com/Miceuz/PlantWateringAlarm) project. There is also an [RS485](https://github.com/Miceuz/rs485-moist-sensor) and an [analog](https://github.com/Miceuz/soil-moisture-sensor-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
+```arduino
+#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:
+```arduino
+#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
+}
+```
+