Revision 0:d2e26e6fa11b, committed 2021-04-06

Comitter:

MarioBlazevic

Date:

Tue Apr 06 12:12:07 2021 +0000

Commit message:

Changed in this revision

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

diff -r 000000000000 -r d2e26e6fa11b dht11.h
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/dht11.h	Tue Apr 06 12:12:07 2021 +0000
@@ -0,0 +1,74 @@
+#ifndef DHT11_H
+#define DHT11_H
+ 
+#include "mbed.h"
+ 
+#define DHTLIB_OK                0
+#define DHTLIB_ERROR_CHECKSUM   -1
+#define DHTLIB_ERROR_TIMEOUT    -2
+ 
+/** Class for the DHT11 sensor.
+ * 
+ * Example:
+ * @code
+ * #include "mbed.h"
+ * #include "Dht11.h"
+ *
+ * Serial pc(USBTX, USBRX);
+ * Dht11 sensor(PTD7);
+ * 
+ * int main() {
+ *     sensor.read();
+ *     pc.printf("T: %f, H: %d\r\n", sensor.getFahrenheit(), sensor.getHumidity());
+ * }
+ * @endcode
+ */
+class Dht11
+{
+public:
+    /** Construct the sensor object.
+     *
+     * @param pin PinName for the sensor pin.
+     */
+    Dht11(PinName const &p);
+    
+    /** Update the humidity and temp from the sensor.
+     *
+     * @returns
+     *   0 on success, otherwise error.
+     */
+    int read();
+    
+    /** Get the temp(f) from the saved object.
+     *
+     * @returns
+     *   Fahrenheit float
+     */
+    float getFahrenheit();
+    
+    /** Get the temp(c) from the saved object.
+     *
+     * @returns
+     *   Celsius int
+     */
+    int getCelsius();
+    
+    /** Get the humidity from the saved object.
+     *
+     * @returns
+     *   Humidity percent int
+     */
+    int getHumidity();
+ 
+private:
+    /// percentage of humidity
+    int _humidity;
+    /// celsius
+    int _temperature;
+    /// pin to read the sensor info on
+    DigitalInOut _pin;
+    /// times startup (must settle for at least a second)
+    Timer _timer;
+};
+ 
+#endif