Revision 12:31645d013d6c, committed 2017-04-05

Comitter:

ledonger

Date:

Wed Apr 05 13:14:12 2017 +0000

Parent:

11:1379308ecace

Commit message:

Solved problem while reading data, because of an offset of 20?s before the sensor takes control of the data bus

Changed in this revision

diff -r 1379308ecace -r 31645d013d6c main.cpp
--- a/main.cpp	Tue Jan 20 02:21:22 2015 +0000
+++ b/main.cpp	Wed Apr 05 13:14:12 2017 +0000
@@ -1,5 +1,7 @@
 #include "mbed.h"
 
+//Tested with success on STM32 Nucleo L476
+
 DigitalOut myled(LED1); // Activate LED
 DigitalIn mybutton(USER_BUTTON); // Activate button
 DigitalInOut data_pin(A0); // Activate digital in
@@ -9,30 +11,34 @@
 uint64_t adat; // 64 bit variable for temporary data
 int i;
 
+
 // Function to initialize DHT11
 void dht_read(void) {
-    data_pin.output(); // Set A0 as output
+    data_pin.output(); 
     // Initialize measurement > 18 ms low
     data_pin = 0;
     wait_ms(20);
     // After high and release the pin switch input mode
     data_pin = 1;
+    
+    wait_us(20);//Wait for the sensor to take control and set low level /!\ Important
+    
     data_pin.input();
     // Wait until the end of 80 us low
-    while(!data_pin.read()) {}
+    while(!data_pin.read());
     // Wait until end of 80 us high
-    while(data_pin.read()) {}
+    while(data_pin.read());
     // 40 bit, 40 read out cycle
     for(i=0; i<40; i++) {
         adat = adat << 1; // Shift for new number
         tmr.stop(); // Stop timer if runs
         tmr.reset();  // Reset timer
         // Wait until pin
-        while(!data_pin.read()) {}          
+        while(!data_pin.read());       
         tmr.start();            
-        while(data_pin.read()) {}
+        while(data_pin.read());
         // If DHT11 HIGH longer than 40 micro seconds (hopefully 70 us)
-        if(tmr.read_us() > 40) {
+        if(tmr.read_us() > 50) {
             // bit is 1
             adat++;
         }
@@ -42,20 +48,29 @@
 int main() {
     pc.printf("Read the DHT11 temperature and humidity sensor!\n"); //Welcome message
     while(1) {
-        if (mybutton == 0) { // Button is pressed
+        if(mybutton == 0){ // Button is pressed
             // Reset adat variable
             adat = 0;
             myled = 1; // LED is ON
             dht_read(); // Call the function
             // Send result through UART result
-            pc.printf("%d", (adat  & 0x000000ff00000000) >> 32); // Humidity
-            pc.printf("\n\r"); // Send a new line and carriage return.
-            pc.printf("%d", (adat & 0x0000000000ff0000) >> 16 ); // Temperature
-            pc.printf("\n\r");
-            pc.printf("%d", adat & 0x00000000000000ff); // Checksum.
-            pc.printf("\n\r");
-            wait_ms(200); // Wait 0.2 sec till continue.
-        } else {
+            //pc.printf("Raw data:%10x\n\r",adat);
+            pc.printf("Humidity:%d%%\n\r", (adat  & 0x000000ff00000000) >> 32); // Humidity
+            pc.printf("Temperature:%d degrees\n\r", (adat & 0x0000000000ff0000) >> 16 ); // Temperature
+            if((adat&0x00000000000000ff) == ((adat&0x000000ff00000000) >> 32) + ((adat&0x00000000ff000000) >> 24)
+                + ((adat&0x0000000000ff0000) >> 16) + ((adat&0x000000000000ff00) >> 8)){
+                pc.printf("Checksum : OK\n\r");        
+            }
+            else{
+                pc.printf("Checksum : Error\n\r");   
+            }
+            
+            //pc.printf("Checksum:%d\n\r", adat & 0x00000000000000ff); // Checksum.
+            /*pc.printf("Checksum calculated:%d\n\r",((adat&0x000000ff00000000) >> 32) + ((adat  & 0x00000000ff000000) >> 24)
+                + ((adat & 0x0000000000ff0000) >> 16) + ((adat & 0x000000000000ff00) >> 8));*/
+            wait_ms(300); // Wait 0.2 sec till continue.
+        } 
+        else{
             myled = 0; // LED is OFF
         }
     }

diff -r 1379308ecace -r 31645d013d6c mbed.bld
--- a/mbed.bld	Tue Jan 20 02:21:22 2015 +0000
+++ b/mbed.bld	Wed Apr 05 13:14:12 2017 +0000
@@ -1,1 +1,1 @@
-http://mbed.org/users/mbed_official/code/mbed/builds/4fc01daae5a5
\ No newline at end of file
+https://mbed.org/users/mbed_official/code/mbed/builds/856d2700e60b
\ No newline at end of file