Added DHT prototypes.

Added the beginning of the DHT code which will likely be used
in part 4 of the tutorial series.

Signed-off-by: A.M. Rowsell <amrowsell@frozenelectronics.ca>

dht.c

@@ -0,0 +1,27 @@
+#include <stdint.h>
+#include "user_interface.h"
+#include "os_type.h"
+#include "osapi.h"
+#include "gpio.h"
+#include "dht.h"
+
+#define DHTBus BIT4
+
+LOCAL uint8_t ICACHE_FLASH_ATTR getBitNum(uint32_t bit) {
+  uint32_t localBit = bit;
+  for(uint8_t i = 0; i <= 16; i++) {
+    localBit >>= i;
+    if(bit & 0x01) {
+      return i;
+    }
+  }
+  return -1; // if we reached this spot we received a bad number
+}
+void ICACHE_FLASH_ATTR setupDHT(void) {
+  gpio_output_set(0, DHTBus, 0, DHTBus); // set up DHTBus as active low output
+  ETS_GPIO_INTR_ATTACH(func, NULL);
+}
+
+void ICACHE_FLASH_ATTR getDHTData(void) {
+  
+}