Diff: dht22.h

Revision:

0:e50b1c66ec57

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dht22.h	Sun Apr 21 03:29:29 2019 +0000
@@ -0,0 +1,39 @@
+/*
+ * (C) The University of Kent and Simon Cooksey 2015.
+ */
+
+#ifndef __DHT22_h_
+#define __DHT22_h_
+
+// We'll pick a point to decide if a signal is 1 or 0 from. 
+#define DHT22_SIGNAL_HIGH_LOW_BOUNDARY      50   // uS
+#define DHT22_START_BIT_TIME                500  // uS
+#define DHT22_START_BIT_RESPONSE            80   // uS
+
+typedef enum {
+    EDGE_TYPE_FALLING,
+    EDGE_TYPE_RISING,
+} edge_type_t;
+
+typedef struct {
+    int temp;
+    int humidity;
+    uint8_t checksum;
+} DHT22_data_t;
+
+class DHT22 {
+public:
+    DHT22(PinName pin)  : dht22_s(pin) { }
+    void read(DHT22_data_t * data);
+private:
+    DigitalInOut dht22_s;
+    Timer dht22_t;
+
+    int wait_for_edge(edge_type_t type);
+    void send_start();
+    void await_start_response();
+    int16_t read_word();
+    uint8_t read_checksum();
+};
+
+#endif // __DHT22_h_