Serge Sozonoff / SHT2x

Port of the SHT2x example code from Sensirion

Dependents:   sht21_test ENVLogger

Diff: SHT2x.cpp

Revision:
2:2464fed17980
Parent:
1:d0f691423bf1
--- a/SHT2x.cpp	Sat Apr 23 18:10:56 2011 +0000
+++ b/SHT2x.cpp	Sat Apr 23 19:07:52 2011 +0000
@@ -1,18 +1,32 @@
-//
-//    S E N S I R I O N   AG,  Laubisruetistr. 50, CH-8712 Staefa, Switzerland
-//==============================================================================//
-// Project   :  SHT2x Sample Code (V1.2)
-// File      :  SHT2x.c
-// Author    :  MST
-// Controller:  NEC V850/SG3 (uPD70F3740)
-// Compiler  :  IAR compiler for V850 (3.50A)
-// Brief     :  Sensor layer. Functions for sensor access
-//==============================================================================//
-//---------- Includes ----------------------------------------------------------
+/*
+    Permission is hereby granted, free of charge, to any person obtaining a copy
+    of this software and associated documentation 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
+    furnished 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 FOR 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.
+*/
+
+//=============================================================================
+// Port of the SHT21 example code from Sensirion
+// port by Serge Sozonoff
+//=============================================================================
+
 #include "SHT2x.h"
 #include "mbed.h"
 
-SHT2x::SHT2x (PinName p_sda, PinName p_scl) : i2c(p_sda, p_scl), out(USBTX, USBRX)  {
+SHT2x::SHT2x (PinName p_sda, PinName p_scl) : i2c(p_sda, p_scl)  {
 }
 
 //==============================================================================//
@@ -32,6 +46,15 @@
     if (crc != checksum) return CHECKSUM_ERROR;
     else return 0;
 }
+
+//===========================================================================//
+int SHT2x::i2cWrite(int data)
+//===========================================================================//
+{
+    if (i2c.write(data) < 1) return ACK_ERROR;
+    else return 0;
+}
+
 //===========================================================================//
 int SHT2x::SHT2x_ReadUserRegister(int *pRegisterValue)
 //===========================================================================//
@@ -40,11 +63,11 @@
     int error=0;    //variable for error code
 
     i2c.start();
-    i2c.write(I2C_ADR_W);
-    i2c.write(USER_REG_R);
+    error |= i2cWrite(I2C_ADR_W);
+    error |= i2cWrite(USER_REG_R);
 
     i2c.start();
-    i2c.write(I2C_ADR_R);
+    error |= i2cWrite(I2C_ADR_R);
 
 
     *pRegisterValue = i2c.read(ACK);
@@ -63,9 +86,9 @@
     int error=0;   //variable for error code
     i2c.start();
 
-    i2c.write(I2C_ADR_W);
-    i2c.write(USER_REG_W);
-    i2c.write(*pRegisterValue);
+    error |= i2cWrite(I2C_ADR_W);
+    error |= i2cWrite(USER_REG_W);
+    error |= i2cWrite(*pRegisterValue);
     i2c.stop();
 
     return error;
@@ -82,21 +105,24 @@
     //-- write I2C sensor address and command --
     i2c.start();
 
-    i2c.write(I2C_ADR_W); // I2C Adr
+    error |= i2cWrite(I2C_ADR_W); // I2C Adr
     switch (eSHT2xMeasureType) {
         case HUMIDITY:
-            i2c.write(TRIG_RH_MEASUREMENT_HM);
+            error |= i2cWrite(TRIG_RH_MEASUREMENT_HM);
             break;
         case TEMP:
-            i2c.write(TRIG_T_MEASUREMENT_HM);
+            error |= i2cWrite(TRIG_T_MEASUREMENT_HM);
             break;
         default:
             break;
     }
-    
+
     //-- wait until hold master is released --
     i2c.start();
-    i2c.write(I2C_ADR_R);
+
+    __disable_irq();     // Disable Interrupts
+
+    error |= i2cWrite(I2C_ADR_R);
 
     //SCL=HIGH;                     // set SCL I/O port as input
     i2c.sclAsInput();
@@ -119,6 +145,9 @@
     *pMeasurand |= data[1];
 
     checksum = i2c.read(NoACK);
+
+    __enable_irq();     // Enable Interrupts
+
     //-- verify checksum --
     error |= SHT2x_CheckCrc (data, 2, checksum);
 
@@ -137,13 +166,13 @@
     //-- write I2C sensor address and command --
     i2c.start();
 
-    i2c.write(I2C_ADR_W);
+    error |= i2cWrite(I2C_ADR_W);
     switch (eSHT2xMeasureType) {
         case HUMIDITY:
-            i2c.write(TRIG_RH_MEASUREMENT_POLL);
+            error |= i2cWrite(TRIG_RH_MEASUREMENT_POLL);
             break;
         case TEMP:
-            i2c.write(TRIG_T_MEASUREMENT_POLL);
+            error |= i2cWrite(TRIG_T_MEASUREMENT_POLL);
             break;
         default:
             break;
@@ -177,8 +206,8 @@
 {
     int  error=0;           //error variable
     i2c.start();
-    error |= i2c.write(I2C_ADR_W); // I2C Adr
-    error |= i2c.write(SOFT_RESET);                            // Command
+    error |= i2cWrite(I2C_ADR_W); // I2C Adr
+    error |= i2cWrite(SOFT_RESET);                            // Command
     i2c.stop();
     wait_ms(15);
     return error;
@@ -199,10 +228,21 @@
 {
     float temperatureC;            // variable for result
     u16sT &= ~0x0003;           // clear bits [1..0] (status bits)
-    //-- calculate temperature [�C] --
+    //-- calculate temperature [in degrees C] --
     temperatureC= -46.85 + 175.72/65536 *(float)u16sT; //T= -46.85 + 175.72 * ST/2^16
     return temperatureC;
 }
+
+//==============================================================================//
+float SHT2x::SHT2x_GetDewpoint(float h, float t)
+//==============================================================================//
+{
+    float logEx, dew_point;
+    logEx = 0.66077 + 7.5 * t / (237.3 + t) + (log10(h) - 2);
+    dew_point = (logEx - 0.66077) * 237.3 / (0.66077 + 7.5 - logEx);
+    return dew_point;
+}
+
 //==============================================================================//
 int SHT2x::SHT2x_GetSerialNumber(int u8SerialNumber[])
 //==============================================================================//
@@ -210,11 +250,11 @@
     int  error=0;                          //error variable
     //Read from memory location 1
     i2c.start();
-    error |= i2c.write(I2C_ADR_W);
-    error |= i2c.write(0xFA);         //Command for readout on-chip memory
-    error |= i2c.write(0x0F);         //on-chip memory address
+    error |= i2cWrite(I2C_ADR_W);
+    error |= i2cWrite(0xFA);         //Command for readout on-chip memory
+    error |= i2cWrite(0x0F);         //on-chip memory address
     i2c.start();
-    error |= i2c.write(I2C_ADR_R);    //I2C address
+    error |= i2cWrite(I2C_ADR_R);    //I2C address
     u8SerialNumber[5] = i2c.read(ACK); //Read SNB_3
     i2c.read(ACK);                     //Read CRC SNB_3 (CRC is not analyzed)
     u8SerialNumber[4] = i2c.read(ACK); //Read SNB_2
@@ -226,11 +266,11 @@
     i2c.stop();
     //Read from memory location 2
     i2c.start();
-    error |= i2c.write(I2C_ADR_W);    //I2C address
-    error |= i2c.write(0xFC);         //Command for readout on-chip memory
-    error |= i2c.write(0xC9);         //on-chip memory address
+    error |= i2cWrite(I2C_ADR_W);    //I2C address
+    error |= i2cWrite(0xFC);         //Command for readout on-chip memory
+    error |= i2cWrite(0xC9);         //on-chip memory address
     i2c.start();
-    error |= i2c.write(I2C_ADR_R);    //I2C address
+    error |= i2cWrite(I2C_ADR_R);    //I2C address
     u8SerialNumber[1] = i2c.read(ACK); //Read SNC_1
     u8SerialNumber[0] = i2c.read(ACK); //Read SNC_0
     i2c.read(ACK);