Diff: Dht22.cpp

Revision:

2:cc518592dbdb

Parent:

1:5da6f6de3e42

diff -r 5da6f6de3e42 -r cc518592dbdb Dht22.cpp
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/Dht22.cpp	Fri Nov 10 01:00:56 2017 +0000
@@ -0,0 +1,104 @@
+#include "Dht22.h"
+
+Dht22::Dht22(PinName const &p) : _pin(p) {
+    // Set creation time so we can make 
+    // sure we pause at least 1 second for 
+    // startup.
+    _timer.start();
+    
+    _temperature = 0;
+    _humidity = 0;
+}
+
+int Dht22::read()
+{
+    // BUFFER TO RECEIVE
+    uint8_t bits[5];
+    uint8_t cnt = 7;
+    uint8_t idx = 0;
+
+    // EMPTY BUFFER
+    for (int i=0; i< 5; i++) bits[i] = 0;
+    
+    // Verify sensor settled after boot
+    while(_timer.read_ms() < 1500) {}
+    _timer.stop();
+
+    // Notify it we are ready to read
+    _pin.output();
+    _pin = 0;
+    wait_ms(18);
+    _pin = 1;
+    wait_us(40);
+    _pin.input();
+
+    // ACKNOWLEDGE or TIMEOUT
+    unsigned int loopCnt = 10000;
+    while(_pin == 0)
+        if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;
+
+    loopCnt = 10000;
+    while(_pin == 1)
+        if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;
+
+    // READ OUTPUT - 40 BITS => 5 BYTES or TIMEOUT
+    for (int i=0; i<40; i++)
+    {
+        loopCnt = 10000;
+        while(_pin == 0)
+            if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;
+
+        //unsigned long t = micros();
+        Timer t;
+        t. start();
+
+        loopCnt = 10000;
+        while(_pin == 1)
+            if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;
+
+        if (t.read_us() > 40) bits[idx] |= (1 << cnt);
+        if (cnt == 0)   // next byte?
+        {
+            cnt = 7;    // restart at MSB
+            idx++;      // next byte!
+        }
+        else cnt--;
+    }
+
+//    // WRITE TO RIGHT VARS - DHT22
+//    // as bits[1] and bits[3] are allways zero they are omitted in formulas.
+//    _humidity    = bits[0]; 
+//    _temperature = bits[2]; 
+//
+//    uint8_t sum = bits[0] + bits[2];  
+//
+//    if (bits[4] != sum) return DHTLIB_ERROR_CHECKSUM;
+    
+    
+    uint8_t dht22_check_sum;
+    dht22_check_sum = bits[0] + bits[1] + bits[2] + bits[3];
+    //printf("dht22 check sum: %d",dht22_check_sum);
+    dht22_check_sum= dht22_check_sum%256;
+    //printf("dht22 check sum: %d",dht22_check_sum);
+    
+    if (dht22_check_sum == bits[4]) {
+        _humidity = bits[0]*256 + bits[1];
+        
+        _temperature = bits[2]*256 + bits[3];
+        //printf("all good \n");
+        return DHTLIB_OK;
+    }
+    return DHTLIB_ERROR_CHECKSUM;
+}
+
+float Dht22::getFahrenheit() {
+    return((_temperature * 1.8) + 32);
+}
+
+int Dht22::getCelsius() {
+    return(_temperature);
+}
+
+int Dht22::getHumidity() {
+    return(_humidity);
+}