Diff: main.cpp

Revision:

0:7780b0dfed46

Child:

1:89cfea395009

--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/main.cpp	Tue Dec 16 15:00:03 2014 +0000
@@ -0,0 +1,177 @@
+/*
+ *  2014/12/16 Modified by akkera102
+ *
+ *  DHT Library for  Digital-output Humidity and Temperature sensors
+ *
+ *  Works with DHT11
+ *             SEN11301P,  Grove - Temperature&Humidity Sensor     (Seeed Studio)
+ *
+ *  Copyright (C) Wim De Roeve
+ *                based on DHT22 sensor library by HO WING KIT
+ *                Arduino DHT11 library
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documnetation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to  whom the Software is
+ * furished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS OR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "mbed.h"
+
+Serial pc(USBTX, USBRX);
+DigitalInOut pin(p8);
+
+enum {
+    SUCCESS,
+    ERROR_TIMEOUT,
+    ERROR_BUS_BUSY,
+    ERROR_NOT_PRESENT,
+    ERROR_NO_PATIENCE,
+    ERROR_SYNC_TIMEOUT,
+    ERROR_DATA_TIMEOUT,
+    ERROR_CHECKSUM
+};
+
+float Temperature;
+float Humidity;
+
+
+int Stall(int usTimeMax, int level)
+{
+    int usTime = 0;
+
+    while(usTime < usTimeMax)
+    {
+        if(pin == level)
+        {
+            return SUCCESS;
+        }
+
+        usTime++;
+        wait_us(1);
+    }
+
+    return ERROR_TIMEOUT;
+}
+
+int WaitPinHigh(int usTimeOut)
+{
+    return Stall(usTimeOut, 1);
+}
+
+int WaitPinLow(int usTimeOut)
+{
+    return Stall(usTimeOut, 0);
+}
+
+int ReadDHT11(void)
+{
+    // IO must be in hi state to start
+    if(WaitPinHigh(250) == ERROR_TIMEOUT)
+    {
+        return ERROR_BUS_BUSY;
+    }
+
+    // start the transfer
+    pin.output();
+    pin = 0;
+    wait_ms(18);
+
+    pin = 1;
+    wait_us(30);
+
+    pin.input();
+
+    // wait till the sensor grabs the bus
+    if(WaitPinLow(40) == ERROR_TIMEOUT)
+    {
+        return ERROR_NOT_PRESENT;
+    }
+
+    // sensor should signal low 80us and then hi 80us
+    if(WaitPinHigh(100) == ERROR_TIMEOUT)
+    {
+        return ERROR_SYNC_TIMEOUT;
+    }
+    if(WaitPinLow(100) == ERROR_TIMEOUT)
+    {
+        return ERROR_NO_PATIENCE;
+    }
+
+    int i, bit;
+    uint8_t buf[5];
+
+    // capture the data(40 bit)
+    for(i=0; i<5; i++)
+    {
+        buf[i] = 0;
+
+        for(bit=0; bit<8; bit++)
+        {
+            if(WaitPinHigh(75) == ERROR_TIMEOUT)
+            {
+                return ERROR_DATA_TIMEOUT;
+            }
+
+            // logic 0 is 28us max, 1 is 70us
+            wait_us(40);
+            buf[i] |= pin << (7 - bit);
+
+            if(WaitPinLow(50) == ERROR_TIMEOUT)
+            {
+                return ERROR_DATA_TIMEOUT;
+            }
+        }
+    }
+
+    for(i=0; i<5; i++)
+    {
+        printf("buf[%d] = 0x%02x\n", i, buf[i]);
+    }
+
+    // valid check
+    if(buf[4] != buf[0] + buf[1] + buf[2] + buf[3])
+    {
+        return ERROR_CHECKSUM;
+    }
+
+    Temperature = float(buf[2]);
+    Humidity    = float(buf[0]);
+
+    return SUCCESS;
+}
+
+int main(void)
+{
+    int ret;
+
+    for(;;)
+    {
+        ret = ReadDHT11();
+
+        if(ret == SUCCESS)
+        {
+            printf("Temperature : %4.2f\n", Temperature);
+            printf("Humidity    : %4.2f\n", Humidity);
+        }
+        else
+        {
+            printf("Error: %d\n", ret);
+        }
+
+        wait(2);
+    }
+}