drivers/sensors/lm75b/lm75b.c

   1 /**************************************************************************/
   2 /*!
   3     @file     lm75b.c
   4     @author   K. Townsend (microBuilder.eu)
   5     @date     22 March 2010
   6     @version  0.10
   7
   8     @section DESCRIPTION
   9
  10     Driver for NXP's LM75B I2C temperature sensor.  This temperature
  11     sensor has an accuracy of 0.125°C, and returns a temperature value
  12     in degrees celsius where each unit is equal to 0.125°C.  For example,
  13     if the temperature reading is 198, it means that the temperature in
  14     degree celsius is: 198 / 8 = 24.75°C.
  15
  16     @section Example
  17
  18     @code
  19     #include "core/cpu/cpu.h"
  20     #include "drivers/sensors/lm75b/lm75b.h"
  21
  22     int main(void)
  23     {
  24       cpuInit();
  25
  26       int32_t temp = 0;
  27
  28       // Initialise the LM75B
  29       lm75bInit();
  30
  31       while (1)
  32       {
  33         // Get the current temperature (in 0.125°C units)
  34         lm75bGetTemperature(&temp);
  35
  36         // Multiply value by 125 for fixed-point math (0.125°C per unit)
  37         temp *= 125;
  38
  39         // Use modulus operator to display decimal value
  40         printf("Current Temperature: %d.%d C\n", temp / 1000, temp % 1000);
  41
  42         // Alternatively, you could also use floating point math, though
  43         // this will result in larger compiled code if you add in floating
  44         // point support for printf, etc.
  45         //
  46         // float tempFloat = 0.0F;
  47         // lm75bGetTemperature(&temp);
  48         // tempFloat = (float)temp / 8.0F;
  49       }
  50     }
  51     @endcode
  52
  53     @section LICENSE
  54
  55     Software License Agreement (BSD License)
  56
  57     Copyright (c) 2010, microBuilder SARL
  58     All rights reserved.
  59
  60     Redistribution and use in source and binary forms, with or without
  61     modification, are permitted provided that the following conditions are met:
  62     1. Redistributions of source code must retain the above copyright
  63     notice, this list of conditions and the following disclaimer.
  64     2. Redistributions in binary form must reproduce the above copyright
  65     notice, this list of conditions and the following disclaimer in the
  66     documentation and/or other materials provided with the distribution.
  67     3. Neither the name of the copyright holders nor the
  68     names of its contributors may be used to endorse or promote products
  69     derived from this software without specific prior written permission.
  70
  71     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ''AS IS'' AND ANY
  72     EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  73     WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  74     DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
  75     DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  76     (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  77     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  78     ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  79     (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  80     SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  81 */
  82 /**************************************************************************/
  83
  84 #include "lm75b.h"
  85
  86 extern volatile uint8_t   I2CMasterBuffer[I2C_BUFSIZE];
  87 extern volatile uint8_t   I2CSlaveBuffer[I2C_BUFSIZE];
  88 extern volatile uint32_t  I2CReadLength, I2CWriteLength;
  89
  90 static bool _lm75bInitialised = false;
  91
  92 /**************************************************************************/
  93 /*!
  94     @brief  Writes an 8 bit values over I2C
  95 */
  96 /**************************************************************************/
  97 lm75bError_e lm75bWrite8 (uint8_t reg, uint32_t value)
  98 {
  99   // Clear write buffers
 100   uint32_t i;
 101   for ( i = 0; i < I2C_BUFSIZE; i++ )
 102   {
 103     I2CMasterBuffer[i] = 0x00;
 104   }
 105
 106   I2CWriteLength = 3;
 107   I2CReadLength = 0;
 108   I2CMasterBuffer[0] = LM75B_ADDRESS;             // I2C device address
 109   I2CMasterBuffer[1] = reg;                       // Command register
 110   I2CMasterBuffer[2] = (value & 0xFF);            // Value to write
 111   i2cEngine();
 112   return LM75B_ERROR_OK;
 113 }
 114
 115 /**************************************************************************/
 116 /*!
 117     @brief  Reads a 16 bit values over I2C
 118 */
 119 /**************************************************************************/
 120 lm75bError_e lm75bRead16(uint8_t reg, int32_t *value)
 121 {
 122   // Clear write buffers
 123   uint32_t i;
 124   for ( i = 0; i < I2C_BUFSIZE; i++ )
 125   {
 126     I2CMasterBuffer[i] = 0x00;
 127   }
 128
 129   I2CWriteLength = 2;
 130   I2CReadLength = 2;
 131   I2CMasterBuffer[0] = LM75B_ADDRESS;             // I2C device address
 132   I2CMasterBuffer[1] = reg;                       // Command register
 133   // Append address w/read bit
 134   I2CMasterBuffer[2] = LM75B_ADDRESS | LM75B_READBIT;
 135   i2cEngine();
 136
 137   // Shift values to create properly formed integer
 138   *value = ((I2CSlaveBuffer[0] << 8) | I2CSlaveBuffer[1]) >> 5;
 139
 140   //  Sign extend negative numbers
 141   if (I2CSlaveBuffer[0] & 0x80)
 142   {
 143     // Negative number
 144     *value |= 0xFFFFFC00;
 145   }
 146   return LM75B_ERROR_OK;
 147 }
 148
 149 /**************************************************************************/
 150 /*!
 151     @brief  Initialises the I2C block
 152 */
 153 /**************************************************************************/
 154 lm75bError_e lm75bInit(void)
 155 {
 156   // Initialise I2C
 157   if (i2cInit(I2CMASTER) == false)
 158   {
 159     return LM75B_ERROR_I2CINIT;    /* Fatal error */
 160   }
 161
 162   _lm75bInitialised = true;
 163
 164   return LM75B_ERROR_OK;
 165
 166   // Set device to shutdown mode by default (saves power)
 167   return lm75bConfigWrite (LM75B_CONFIG_SHUTDOWN_SHUTDOWN);
 168 }
 169
 170 /**************************************************************************/
 171 /*!
 172     @brief  Reads the current temperature from the LM75B
 173
 174     @note   This method will assign a signed 32-bit value (int32) to 'temp',
 175             where each unit represents +/- 0.125°C.  To convert the numeric
 176             value to degrees celsius, you must divide the value of 'temp'
 177             by 8.  This conversion is not done automatically, since you may
 178             or may not want to use floating point math for the calculations.
 179 */
 180 /**************************************************************************/
 181 lm75bError_e lm75bGetTemperature (int32_t *temp)
 182 {
 183   if (!_lm75bInitialised) lm75bInit();
 184
 185   // Turn device on
 186   lm75bConfigWrite (LM75B_CONFIG_SHUTDOWN_POWERON);
 187
 188   // Read temperature
 189   lm75bError_e error = LM75B_ERROR_OK;
 190   error = lm75bRead16 (LM75B_REGISTER_TEMPERATURE, temp);
 191
 192   // Shut device back down
 193   lm75bConfigWrite (LM75B_CONFIG_SHUTDOWN_SHUTDOWN);
 194
 195   return error;
 196 }
 197
 198 /**************************************************************************/
 199 /*!
 200     @brief  Writes the supplied 8-bit value to the LM75B config register
 201 */
 202 /**************************************************************************/
 203 lm75bError_e lm75bConfigWrite (uint8_t configValue)
 204 {
 205   if (!_lm75bInitialised) lm75bInit();
 206
 207   return lm75bWrite8 (LM75B_REGISTER_CONFIGURATION, configValue);
 208 }