drivers/dac/mcp4725/mcp4725.c

   1 /**************************************************************************/
   2 /*!
   3     @file     mcp4725.c
   4     @author   K. Townsend (microBuilder.eu)
   5
   6     @brief    Driver for the I2C-based MCP4725 12-Bit DAC.
   7
   8     @section Example
   9
  10     @code
  11     #include "drivers/dac/mcp4725/mcp4725.h"
  12     ...
  13
  14     mcp4725Init();
  15
  16     // Set the voltage to 50% of vref and don't save the value in EEPROM
  17     mcp4725SetVoltage(2048, false);
  18
  19     // Request the current value from the DAC
  20     uint8_t status = 0;
  21     uint16_t value = 0;
  22     mcp4725ReadConfig(&status, &value);
  23
  24     @endcode
  25
  26     @section LICENSE
  27
  28     Software License Agreement (BSD License)
  29
  30     Copyright (c) 2010, microBuilder SARL
  31     All rights reserved.
  32
  33     Redistribution and use in source and binary forms, with or without
  34     modification, are permitted provided that the following conditions are met:
  35     1. Redistributions of source code must retain the above copyright
  36     notice, this list of conditions and the following disclaimer.
  37     2. Redistributions in binary form must reproduce the above copyright
  38     notice, this list of conditions and the following disclaimer in the
  39     documentation and/or other materials provided with the distribution.
  40     3. Neither the name of the copyright holders nor the
  41     names of its contributors may be used to endorse or promote products
  42     derived from this software without specific prior written permission.
  43
  44     THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS ''AS IS'' AND ANY
  45     EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED
  46     WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE
  47     DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER BE LIABLE FOR ANY
  48     DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES
  49     (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  50     LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND
  51     ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  52     (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  53     SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  54 */
  55 /**************************************************************************/
  56 #include "mcp4725.h"
  57 #include "core/i2c/i2c.h"
  58
  59 extern volatile uint8_t   I2CMasterBuffer[I2C_BUFSIZE];
  60 extern volatile uint8_t   I2CSlaveBuffer[I2C_BUFSIZE];
  61 extern volatile uint32_t  I2CReadLength, I2CWriteLength;
  62
  63 static bool _mcp4725Initialised = false;
  64
  65 /**************************************************************************/
  66 /*!
  67     @brief Initialises I2C for the MCP4725.
  68 */
  69 /**************************************************************************/
  70 int mcp4725Init()
  71 {
  72   // Initialise I2C
  73   if (i2cInit(I2CMASTER) == false)
  74   {
  75     /* Fatal error */
  76     return -1;
  77   }
  78
  79   /* Set initialisation flag */
  80   _mcp4725Initialised = true;
  81
  82   return 0;
  83 }
  84
  85 /**************************************************************************/
  86 /*!
  87     @brief  Sets the output voltage to a fraction of source vref.  (Value
  88             can be 0..4095)
  89
  90     @param[in]  output
  91                 The 12-bit value representing the relationship between
  92                 the DAC's input voltage and its output voltage.
  93     @param[in]  writeEEPROM
  94                 If this value is true, 'output' will also be written
  95                 to the MCP4725's internal non-volatile memory, meaning
  96                 that the DAC will retain the current voltage output
  97                 after power-down or reset.
  98 */
  99 /**************************************************************************/
 100 void mcp4725SetVoltage( uint16_t output, bool writeEEPROM )
 101 {
 102   if (!_mcp4725Initialised) mcp4725Init();
 103
 104   // Clear write buffers
 105   uint32_t i;
 106   for ( i = 0; i < I2C_BUFSIZE; i++ )
 107   {
 108     I2CMasterBuffer[i] = 0x00;
 109   }
 110
 111   I2CWriteLength = 4;
 112   I2CReadLength = 0;
 113   I2CMasterBuffer[0] = MCP4725_ADDRESS;                 // I2C device address
 114   if (writeEEPROM)                                      // command and config bits  (C2.C1.C0.x.x.PD1.PD0.x)
 115   {
 116     I2CMasterBuffer[1] = (MCP4726_CMD_WRITEDACEEPROM);
 117   }
 118   else
 119   {
 120     I2CMasterBuffer[1] = (MCP4726_CMD_WRITEDAC);
 121   }
 122   I2CMasterBuffer[2] = (output / 16);                   // Upper data bits          (D11.D10.D9.D8.D7.D6.D5.D4)
 123   I2CMasterBuffer[3] = (output % 16) << 4;              // Lower data bits          (D3.D2.D1.D0.x.x.x.x)
 124   i2cEngine();
 125 }
 126
 127 /**************************************************************************/
 128 /*!
 129     @brief  Reads the current configuration and output settings for the
 130             DAC.
 131
 132     @param[out] status
 133                 Pointer to hold the contents of the status register
 134     @param[out] value
 135                 Pointer to hold the output value of the 12-bit DAC
 136 */
 137 /**************************************************************************/
 138 void mcp4725ReadConfig( uint8_t *status, uint16_t *value )
 139 {
 140   if (!_mcp4725Initialised) mcp4725Init();
 141
 142   // Clear write buffers
 143   uint32_t i;
 144   for ( i = 0; i < I2C_BUFSIZE; i++ )
 145   {
 146     I2CMasterBuffer[i] = 0x00;
 147   }
 148
 149   I2CWriteLength = 1;
 150   I2CReadLength = 3;
 151   I2CMasterBuffer[0] = MCP4725_ADDRESS | MCP4725_READ;
 152   i2cEngine();
 153
 154   // Shift values to create properly formed integers
 155   *status = I2CSlaveBuffer[0];
 156   *value = ((I2CSlaveBuffer[1] << 4) | (I2CSlaveBuffer[2] >> 4));
 157 }
 158