Merge branch 'master' of https://github.com/adafruit/Adafruit-Raspberry-Pi-Python-Code

Author: K. Townsend

Adafruit_DHT_Driver/Adafruit_DHT.c

@@ -0,0 +1,128 @@
+//  How to access GPIO registers from C-code on the Raspberry-Pi
+//  Example program
+//  15-January-2012
+//  Dom and Gert
+//
+
+
+// Access from ARM Running Linux
+
+#define BCM2708_PERI_BASE        0x20000000
+#define GPIO_BASE                (BCM2708_PERI_BASE + 0x200000) /* GPIO controller */
+
+
+#include <stdio.h>
+#include <string.h>
+#include <stdlib.h>
+#include <dirent.h>
+#include <fcntl.h>
+#include <assert.h>
+#include <unistd.h>
+#include <sys/mman.h>
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <bcm2835.h>
+#include <unistd.h>
+
+#define DHTPIN RPI_GPIO_P1_07
+#define MAXTIMINGS 100
+
+#define DHT11 11
+#define DHT22 22
+#define AM2302 22
+
+int readDHT(int type, int pin);
+
+int main(int argc, char **argv)
+{
+  if (!bcm2835_init())
+        return 1;
+
+  if (argc != 2) {
+	printf("usage: %s [11|22|2302]\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], "2303") == 0) type = AM2302;
+  if (type == 0) {
+	printf("Select 11, 22, 2303 as type!\n");
+	return 3;
+  }
+
+  readDHT(type, DHTPIN);
+  return 0;
+
+} // main
+
+
+int bits[250], data[100];
+int bitidx = 0;
+
+int readDHT(int type, int pin) {
+  int counter = 0;
+  int laststate = HIGH;
+  int j=0;
+
+  // Set GPIO pin to output
+  bcm2835_gpio_fsel(pin, BCM2835_GPIO_FSEL_OUTP);
+  bcm2835_gpio_write(pin, HIGH);
+  usleep(100);
+  bcm2835_gpio_write(pin, LOW);
+  usleep(20000);
+  bcm2835_gpio_fsel(pin, BCM2835_GPIO_FSEL_INPT);
+
+  data[0] = data[1] = data[2] = data[3] = data[4] = 0;
+  // read data!
+  for (int i=0; i< MAXTIMINGS; i++) {
+    counter = 0;
+    while ( bcm2835_gpio_lev(pin) == laststate) {
+	counter++;
+	nanosleep(1);		// overclocking might change this?
+        if (counter == 100)
+	  break;
+    }
+    laststate = bcm2835_gpio_lev(pin);
+    if (counter == 100) break;
+    bits[bitidx++] = counter;
+
+    if ((i>3) && (i%2 == 0)) {
+      // shove each bit into the storage bytes
+      data[j/8] <<= 1;
+      if (counter > 16)
+        data[j/8] |= 1;
+      j++;
+    }
+  }
+
+
+#ifdef DEBUG
+  for (int i=3; i<bitidx; i+=2) {
+    printf("bit %d: %d\n", i-3, bits[i]);
+    printf("bit %d: %d (%d)\n", i-2, bits[i+1], bits[i+1] > 15);
+  }
+#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 ((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 == 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);
+    }
+    return 1;
+  }
+
+  return 0;
+}