Diff: main.cpp

Revision:

0:8253de48776b

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Wed Jan 13 12:52:35 2016 +0000
@@ -0,0 +1,75 @@
+#include "mbed.h"
+
+#define EEPROM_ADDR   (0b10100000) // EEPROM address
+
+I2C i2c(I2C_SDA, I2C_SCL);
+DigitalOut myled(LED1); // Activate LED
+DigitalIn mybutton(USER_BUTTON); // Activate button
+DigitalInOut data_pin(A0); // Activate digital in
+Serial pc(SERIAL_TX, SERIAL_RX); // Initialize UART connection
+// Use a terminal program (eg. putty).
+Timer tmr; //initialize timer
+uint64_t adat; // 64 bit variable for temporary data
+int i;
+char data_write[4]; //Array for address and data
+char eeprom_read_address[2] = {0, 0};
+char data_read[2];
+
+// Function to initialize DHT11
+void dht_read(void)
+{
+    data_pin.output(); // Set A0 as output
+    // Initialize measurement > 18 ms low
+    data_pin = 0;
+    wait_ms(20);
+    // After high and release the pin switch input mode
+    data_pin = 1;
+    data_pin.input();
+    // Wait until the end of 80 us low
+    while(!data_pin.read()) {}
+    // Wait until end of 80 us high
+    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()) {}
+        tmr.start();
+        while(data_pin.read()) {}
+        // If DHT11 HIGH longer than 40 micro seconds (hopefully 70 us)
+        if(tmr.read_us() > 40) {
+            // bit is 1
+            adat++;
+        }
+    }
+}
+
+int main()
+{
+    pc.printf("Log the DHT11 temperature and humidity sensor!\n\r"); //Welcome message
+    while(1) {
+        if (mybutton == 0) { // Button is pressed
+            pc.printf("\n\rLogged humidity and temperature:\n\r"); //Welcome message
+            myled = 1; // LED is ON
+            i2c.write(EEPROM_ADDR, eeprom_read_address, 2, true);
+            for( i=0; i < 30; i++ ) {
+                i2c.read(EEPROM_ADDR, data_read, 2);
+                pc.printf("%d %d\n\r",data_read[0], data_read[1]);
+            }
+            wait(3); // Wait 0.2 sec till continue.
+        } else {
+            myled =1;
+            wait(0.1);
+            adat = 0; // Resed global adat variable
+            dht_read(); // Call the function
+            // Save data to EEPROM
+            data_write[2] = (adat  & 0x000000ff00000000) >> 32; // Humidity
+            data_write[3] = (adat & 0x0000000000ff0000) >> 16 ; // Temperature
+            i2c.write(EEPROM_ADDR, data_write, 4);
+            myled = 0; // LED is OFF
+            wait(1.8);
+        }
+    }
+}