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AM2320.cpp
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AM2320.cpp
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#include "AM2320.h"
#include <Wire.h>
AM2320::AM2320()
{
}
int AM2320::Read()
{
Wake();
bool result = Prepare();
if (!result)
return 1; //Failed.
delayMicroseconds(1550); //Wait for > 1500us
Wire.requestFrom(ADDRESS, 8);
memset(_buf, 0, 8);
for (byte i = 0; i < 8; i++)
_buf[i] = Wire.read();
unsigned int crc = _buf[7] << 8;
crc += _buf[6];
if (crc != CRC16(_buf, 6))
return 2; //CRC Check failed
unsigned int humidity = (_buf[2] << 8) + _buf[3];
_humidity = humidity / 10.0;
unsigned int temperature = ((_buf[4] & 0x7F) << 8) + _buf[5];
_temperature = temperature / 10.0;
return 0;
}
void AM2320::Wake()
{
Wire.beginTransmission(ADDRESS);
Wire.endTransmission();
}
bool AM2320::Prepare()
{
Wire.beginTransmission(ADDRESS);
Wire.write(0x03); //Function code - Read Register Data
Wire.write(0x00); //Start address
Wire.write(0x04); //Bytes to read
return Wire.endTransmission(true) == 0;
}
float AM2320::Humidity()
{
return _humidity;
}
float AM2320::Temperature()
{
return _temperature;
}
unsigned int AM2320::CRC16(byte* ptr, byte length)
{
unsigned short crc = 0xFFFF;
while(length--)
{
crc ^= *ptr++;
for (byte i = 0; i < 8; i++)
{
if ((crc & 0x01) != 0)
{
crc >>= 1;
crc ^= 0xA001;
}
else
{
crc >>= 1;
}
}
}
return crc;
}