Adds ctypes wrapper for DHT sensors

Adafruit_DHT_Driver/Adafruit_DHT.c

@@ -33,7 +33,9 @@
 #define DHT22 22
 #define AM2302 22
 
-int readDHT(int type, int pin);
+float *readDHT(int type, int pin, int print);
+int parseType(char *input);
+int init(void);
 
 int main(int argc, char **argv)
 {
@@ -45,10 +47,9 @@ int main(int argc, char **argv)
 	printf("example: %s 2302 4 - Read from an AM2302 connected to GPIO #4\n", argv[0]);
 	return 2;
   }
-  int type = 0;
-  if (strcmp(argv[1], "11") == 0) type = DHT11;
-  if (strcmp(argv[1], "22") == 0) type = DHT22;
-  if (strcmp(argv[1], "2302") == 0) type = AM2302;
+
+  int type = parseType(argv[1]);
+
   if (type == 0) {
 	printf("Select 11, 22, 2302 as type!\n");
 	return 3;
@@ -63,20 +64,33 @@ int main(int argc, char **argv)
 
 
   printf("Using pin #%d\n", dhtpin);
-  readDHT(type, dhtpin);
+
+  float *r = readDHT(type, dhtpin, 1);
+  if (r[0]==-1.){
+	  printf("Read failed\n");
+  } else {
+	  if (type == DHT11) printf("Temp =  %.0f *C, Hum = %.0f \%\n", r[0], r[1]);
+	  if (type == DHT22) printf("Temp =  %.1f *C, Hum = %.1f \%\n", r[0], r[1]);
+  }
+
   return 0;
 
 } // main
 
 
-int bits[250], data[100];
-int bitidx = 0;
 
-int readDHT(int type, int pin) {
+
+float *readDHT(int type, int pin, int print) {
+  int bits[250], data[100];
+  int bitidx = 0;
+
   int counter = 0;
   int laststate = HIGH;
   int j=0;
 
+  static float result[2];
+  float t, h;
+
   // Set GPIO pin to output
   bcm2835_gpio_fsel(pin, BCM2835_GPIO_FSEL_OUTP);
 
@@ -124,25 +138,41 @@ int readDHT(int type, int pin) {
   }
 #endif
 
-  printf("Data (%d): 0x%x 0x%x 0x%x 0x%x 0x%x\n", j, data[0], data[1], data[2], data[3], data[4]);
+  if (print) printf("Data (%d): 0x%x 0x%x 0x%x 0x%x 0x%x\n", j, data[0], data[1], data[2], data[3], data[4]);
 
-  if ((j >= 39) &&
-      (data[4] == ((data[0] + data[1] + data[2] + data[3]) & 0xFF)) ) {
+  if ((j >= 39) && (data[4] == ((data[0] + data[1] + data[2] + data[3]) & 0xFF)) ) {
      // yay!
-     if (type == DHT11)
-	printf("Temp = %d *C, Hum = %d \%\n", data[2], data[0]);
+     if (type == DHT11) {
+    	 t = (float)data[2];
+    	 h = (float)data[0];
+     }
      if (type == DHT22) {
-	float f, h;
-	h = data[0] * 256 + data[1];
-	h /= 10;
-
-	f = (data[2] & 0x7F)* 256 + data[3];
-        f /= 10.0;
-        if (data[2] & 0x80)  f *= -1;
-	printf("Temp =  %.1f *C, Hum = %.1f \%\n", f, h);
+		//float f, h;
+		h = data[0] * 256 + data[1];
+		h /= 10;
+
+		t = (data[2] & 0x7F)* 256 + data[3];
+		t /= 10.0;
+		if (data[2] & 0x80)  t *= -1;
     }
-    return 1;
+    result[0] = t;
+    result[1] = h;
+    return result;
   }
+  result[0] = -1.;
+  result[1] = -1.;
+  return result;
+}
 
-  return 0;
+int parseType(char *input){
+	int type = 0;
+	if (strcmp(input, "11") == 0) type = DHT11;
+	if (strcmp(input, "22") == 0) type = DHT22;
+	if (strcmp(input, "2302") == 0) type = AM2302;
+	return type;
+}
+
+int init(void){
+	if (bcm2835_init()) return 1;
+	return 0;
 }

Adafruit_DHT_Driver/Adafruit_DHT_googledocs.ex.py

@@ -6,6 +6,7 @@
 import time
 import datetime
 import gspread
+from DHT_Wrapper import DHT
 
 # ===========================================================================
 # Google Account Details
@@ -37,31 +38,25 @@
   print "Unable to open the spreadsheet.  Check your filename: %s" % spreadsheet
   sys.exit()
 
+# Initialize sensor
+d = DHT("2302", 4)
+
 # Continuously append data
 while(True):
   # Run the DHT program to get the humidity and temperature readings!
-
-  output = subprocess.check_output(["./Adafruit_DHT", "2302", "4"]);
-  print output
-  matches = re.search("Temp =\s+([0-9.]+)", output)
-  if (not matches):
-	time.sleep(3)
-	continue
-  temp = float(matches.group(1))
+  r = d.read()
 
-  # search for humidity printout
-  matches = re.search("Hum =\s+([0-9.]+)", output)
-  if (not matches):
-	time.sleep(3)
-	continue
-  humidity = float(matches.group(1))
+  if not r:
+      time.sleep(3)
+      continue
+
 
-  print "Temperature: %.1f C" % temp
-  print "Humidity:    %.1f %%" % humidity
+  print "Temperature: %.1f C" % r["temp"]
+  print "Humidity:    %.1f %%" % r["hum"]
 
   # Append the data in the spreadsheet, including a timestamp
   try:
-    values = [datetime.datetime.now(), temp, humidity]
+    values = [datetime.datetime.now(), r["temp"], r["hum"]]
     worksheet.append_row(values)
   except:
     print "Unable to append data.  Check your connection?"

Adafruit_DHT_Driver/DHT_Wrapper.py

@@ -0,0 +1,29 @@
+import ctypes
+from decimal import *
+
+
+class DHT(object):
+    """
+    Wrapper for Adafruit DHT11/DHT22/AM2302 sensor Raspberry Pi driver.
+    """
+    def __init__(self, sensor, pin):
+        """
+        Initialize with sensor type as string and pin Raspberry Pi pin number as integer
+        """
+        self.DHTlib = ctypes.CDLL("./libAdafruit_DHT.so")
+        if not self.DHTlib.init():
+            raise IOError("Could not initialise BCM2835 - may need to run as root")
+        self.sensor = self.DHTlib.parseType(ctypes.c_char_p(sensor))
+        self.pin = ctypes.c_int(pin)
+        self.DHTlib.readDHT.restype = ctypes.POINTER(ctypes.c_float)
+    def read(self):
+        """
+        Returns a dict of decimals representing measured temperature and humidity
+        """
+        r = self.DHTlib.readDHT(self.sensor, self.pin, ctypes.c_int(0))
+        if r[1] > 0:
+            q = Decimal("0.1")
+            return {"temp": Decimal(r[0]).quantize(q), "hum":Decimal(r[1]).quantize(q)}
+        else:
+            return False
+