TVZ2020
Program očitava temperaturu i vlažnost zraka u prostoriji pomoću senzora DHT11. Očitane vrijednosti ispisuje na računalu u programu Tera Term. Za vlažnost zraka manju od 60% svijetli zelena LED, a za vlažnost zraka veću od 60% pali se crvena LED. Pritiskom na tipkalo prekida se rad programa na 5sekundi. Odbrojavanje se prikazuje na 7-segmentnom displey-u. Za to vrijeme ugašene su sve LED. Nakon isteka 5 sekundi program nastavlja sa radom tamo di je prethodno stao. Žuta LED predstavlja ticker i blinka svake 0,2 sekunde i time pokazuje da se program izvršava.
Diff: dht11.cpp
- Revision:
- 0:d2e26e6fa11b
diff -r 000000000000 -r d2e26e6fa11b dht11.cpp
--- /dev/null Thu Jan 01 00:00:00 1970 +0000
+++ b/dht11.cpp Tue Apr 06 12:12:07 2021 +0000
@@ -0,0 +1,89 @@
+#include "dht11.h"
+
+Dht11::Dht11(PinName const &p) : _pin(p) {
+ // Set creation time so we can make
+ // sure we pause at least 1 second for
+ // startup.
+ _timer.start();
+
+ _temperature = 0;
+ _humidity = 0;
+}
+
+int Dht11::read()
+{
+ // BUFFER TO RECEIVE
+ uint8_t bits[5];
+ uint8_t cnt = 7;
+ uint8_t idx = 0;
+
+ // EMPTY BUFFER
+ for (int i=0; i< 5; i++) bits[i] = 0;
+
+ // Verify sensor settled after boot
+ while(_timer.read_ms() < 1500) {}
+ _timer.stop();
+
+ // Notify it we are ready to read
+ _pin.output();
+ _pin = 0;
+ wait_ms(18);
+ _pin = 1;
+ wait_us(40);
+ _pin.input();
+
+ // ACKNOWLEDGE or TIMEOUT
+ unsigned int loopCnt = 10000;
+ while(_pin == 0)
+ if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;
+
+ loopCnt = 10000;
+ while(_pin == 1)
+ if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;
+
+ // READ OUTPUT - 40 BITS => 5 BYTES or TIMEOUT
+ for (int i=0; i<40; i++)
+ {
+ loopCnt = 10000;
+ while(_pin == 0)
+ if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;
+
+ //unsigned long t = micros();
+ Timer t;
+ t. start();
+
+ loopCnt = 10000;
+ while(_pin == 1)
+ if (loopCnt-- == 0) return DHTLIB_ERROR_TIMEOUT;
+
+ if (t.read_us() > 40) bits[idx] |= (1 << cnt);
+ 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.
+ _humidity = bits[0];
+ _temperature = bits[2];
+
+ uint8_t sum = bits[0] + bits[2];
+
+ if (bits[4] != sum) return DHTLIB_ERROR_CHECKSUM;
+ return DHTLIB_OK;
+}
+
+float Dht11::getFahrenheit() {
+ return((_temperature * 1.8) + 32);
+}
+
+int Dht11::getCelsius() {
+ return(_temperature);
+}
+
+int Dht11::getHumidity() {
+ return(_humidity);
+}
\ No newline at end of file