Arduino调试温湿度传感器AM2321

  1 /*
  2 Measurement of temperature and humidity using the AM2321 sensor
  3 Attention: 
  4     The protocol AM2321 used is not a standard i2c.
  5     Bit-banging is used to wake up the sensor, 
  6     and then i2c functions are used to communicate.
  7 Connection:
  8 AM2321             UNO
  9 VDD <---------->   GND
 10 GND <---------->   GND
 11 SCL <----------> SCL(A5)
 12 SDA <----------> SDA(A4)
 13 */
 14 
 15 #include <Wire.h>
 16 
 17 #define ADDRESS_AM2321 0x5C //not 0xB8
 18 #define SIGN_WRITE 0x00
 19 #define SDA_PIN A4
 20 #define SCL_PIN A5
 21 
 22 byte fuctionCode = 0;
 23 byte dataLength = 0;
 24 byte humiHigh = 0;
 25 byte humiLow = 0;
 26 byte tempHigh = 0;
 27 byte tempLow = 0;
 28 byte crcHigh = 0;
 29 byte crcLow = 0;
 30 
 31 int humidity = 0;
 32 int temperature = 0;
 33 unsigned int crcCode = 0;
 34 
 35 byte backupTWCR = 0;
 36 
 37 void setup()
 38 {
 39     Serial.begin(115200);
 40 }
 41 
 42 void loop()
 43 {
 44     //step 1. wake up the sensor
 45     SendWakeUp(); 
 46     backupTWCR = TWCR;
 47 
 48     //step 2. send command 
 49     Wire.begin();
 50     Wire.beginTransmission(ADDRESS_AM2321);
 51     Wire.write(0x03);
 52     Wire.write(0x00);
 53     Wire.write(0x04);
 54     Wire.endTransmission();
 55 
 56     delayMicroseconds(1500);
 57 
 58     //step 3. read data, and recover the TWCR register
 59     Wire.requestFrom(ADDRESS_AM2321, 8);
 60     fuctionCode = Wire.read();
 61     dataLength = Wire.read();
 62     humiHigh = Wire.read();
 63     humiLow = Wire.read();
 64     tempHigh = Wire.read();
 65     tempLow = Wire.read();
 66     crcLow = Wire.read();
 67     crcHigh = Wire.read();
 68 
 69     //get the result
 70     humidity = (humiHigh<<8) | humiLow;
 71     temperature = (tempHigh<<8) | tempLow;
 72     crcCode = (crcHigh<<8) | crcLow;
 73 
 74     Serial.print(temperature/10.0, 1);    Serial.println(" `C");
 75     Serial.print(humidity/10.0, 1);    Serial.println(" \%RH");
 76     CheckCRC();
 77 
 78     //recover the TWCR register
 79     TWCR = backupTWCR; 
 80 
 81     delay(4000);
 82 }
 83 
 84 void SendWakeUp()
 85 {
 86     //set pinmode
 87     pinMode(SCL_PIN, OUTPUT);
 88     pinMode(SDA_PIN, OUTPUT);
 89     digitalWrite(SCL_PIN, HIGH);
 90     digitalWrite(SDA_PIN, HIGH);
 91 
 92     //issue a START condition
 93     delayMicroseconds(5);
 94     digitalWrite(SDA_PIN, LOW); 
 95     delayMicroseconds(5);
 96     digitalWrite(SCL_PIN, LOW); 
 97     delayMicroseconds(5);
 98 
 99     //send ADDRESS+W
100     shiftOut(SDA_PIN, SCL_PIN, MSBFIRST, ((ADDRESS_AM2321<<1) | SIGN_WRITE));
101 
102     //send clock for ack
103     pinMode(SDA_PIN, INPUT_PULLUP);// or INPUT mode
104     delayMicroseconds(5);
105     digitalWrite(SCL_PIN, HIGH);
106     delayMicroseconds(5);
107     digitalWrite(SCL_PIN, LOW);
108     pinMode(SDA_PIN, OUTPUT);
109     digitalWrite(SDA_PIN, LOW);
110     
111     delayMicroseconds(1000);
112 
113     //issue a STOP condition
114     digitalWrite(SCL_PIN, HIGH);
115     delayMicroseconds(5);
116     digitalWrite(SDA_PIN, HIGH);
117 }
118 
119 void CheckCRC() //from the datesheet
120 {
121     byte backValues[] = {fuctionCode, dataLength, humiHigh, 122         humiLow, tempHigh, tempLow};
123     unsigned int crc = 0xFFFF;
124     int i;
125     int len = 6;
126     int j = 0;
127     while (len--)
128     {
129         crc ^= backValues[j];
130         j++;
131         for (i=0; i<8; i++)
132         {
133             if (crc & 0x01)
134             {
135                 crc >>= 1;
136                 crc ^= 0xA001;
137             }
138             else
139             {
140                 crc >>= 1;
141             }
142         }
143     } 
144     if (crc == crcCode)
145     {
146         Serial.println("CRC checked.");
147     }
148     else
149     {
150         Serial.println("CRC Error!");
151     }
152 }