Diff: main.cpp

Revision:

0:fa2b2a1e9a8f

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Thu Sep 28 02:11:59 2017 +0000
@@ -0,0 +1,117 @@
+#include "mbed.h"
+#include "TextLCD.h"
+
+#define DHTLIB_OK                0
+#define DHTLIB_ERROR_CHECKSUM   -1
+#define DHTLIB_ERROR_TIMEOUT    -2
+
+PinName pin_DHT11 = PA_15;
+
+DigitalInOut data_pin(pin_DHT11);
+
+// rs, rw, e, d0-d3
+TextLCD lcd(PB_12, PB_13, PB_14, PB_15, PA_9, PA_10, PA_11); 
+
+Timer tmr;
+
+int humi;
+int temp;
+
+int dht_read(void);
+
+int main() {
+ 
+    lcd.printf("  Temp :     c\n");
+    lcd.printf("  Humi :     %%"); 
+  
+    while(1) {
+        if(dht_read() == 0)
+        {
+            lcd.locate(10, 0);
+            lcd.printf("%3d", temp);
+            lcd.locate(10, 1);
+            lcd.printf("%3d", humi);
+        }
+        else
+        {
+            lcd.locate(10, 0);
+            lcd.printf("%3d", 0);
+            lcd.locate(10, 1);
+            lcd.printf("%3d", 0);
+        }
+        wait(2);
+    }
+}
+
+int dht_read(void){
+    
+    // BUFFER TO RECEIVE
+    uint8_t bits[5];
+    uint8_t cnt = 7;
+    uint8_t idx = 0;
+    
+    tmr.stop();
+    tmr.reset();
+
+    // EMPTY BUFFER
+    for(int i=0; i< 5; i++) bits[i] = 0;
+
+    // REQUEST SAMPLE
+    data_pin.output();
+    data_pin.write(0);
+    wait_ms(18);
+    data_pin.write(1);
+    wait_us(10);
+    data_pin.input();
+    wait_us(40);
+
+    // ACKNOWLEDGE or TIMEOUT
+    unsigned long loopCnt = 10000;
+    
+    while(data_pin.read() == 0)if(!loopCnt--)return DHTLIB_ERROR_TIMEOUT;
+ 
+    loopCnt = 10000;
+    
+    while(data_pin.read() == 1)if(!loopCnt--)return DHTLIB_ERROR_TIMEOUT;
+
+    // READ OUTPUT - 40 BITS => 5 BYTES or TIMEOUT
+
+    for(int i=0; i<40; i++){
+        
+        loopCnt = 10000;
+        
+        while(data_pin.read() == 0)if(loopCnt-- == 0)return DHTLIB_ERROR_TIMEOUT;
+
+        //unsigned long t = micros();
+        tmr.start();
+
+        loopCnt = 10000;
+        
+        while(data_pin.read())if(!loopCnt--)return DHTLIB_ERROR_TIMEOUT;
+
+        if(tmr.read_us() > 40) bits[idx] |= (1 << cnt);
+        
+        tmr.stop();
+        tmr.reset();
+        
+        if(cnt == 0){   // next byte?
+        
+            cnt = 7;    // restart at MSB
+            idx++;      // next byte!
+            
+        }else cnt--;
+        
+    }
+
+    // WRITE TO RIGHT VARS
+    // as bits[1] and bits[3] are allways zero they are omitted in formulas.
+    humi = bits[0]; 
+    temp = bits[2]; 
+
+    uint8_t sum = bits[0] + bits[1] + bits[2] + bits[3];
+    
+    if(bits[4] != sum){return DHTLIB_ERROR_CHECKSUM;}
+    
+    return DHTLIB_OK;
+    
+}
\ No newline at end of file