title: fatal error: i2c/smbus.h: No such file or directory?
body: <p>I tried to compile some code, and I recieved this response while trying to compile:</p>
  <blockquote>
  <p>./smbus.c:26:23: fatal error: i2c/smbus.h: No such file or directory</p>
  <p>compilation terminated. ./altitude_ai.c: In function</p>
  <p>‘bmp085_Altitude’: ./altitude_ai.c:207:4: warning: implicit</p>
  <p>declaration of function ‘pow’ [-Wimplicit-function-declaration]</p>
  <p>./altitude_ai.c:207:14: warning: incompatible implicit declaration of</p>
  <p>built-in function ‘pow’ [enabled by default]</p>
  </blockquote>
  <p>This is all the code I tried to compile:</p>
  <p><strong>smbus.c</strong></p>
  <pre><code>/*
      smbus.c - SMBus level access helper functions
  
      Copyright (C) 1995-97 Simon G. Vogl
      Copyright (C) 1998-99 Frodo Looijaard &lt;frodol@dds.nl&gt;
      Copyright (C) 2012    Jean Delvare &lt;khali@linux-fr.org&gt;
      Copyright (C) 2012-2013 Donovan Roudabush &lt;sharksfan98@gmail.com&gt;
  
      This program is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published by
      the Free Software Foundation; either version 2 of the License, or
      (at your option) any later version.
  
      This program is distributed in the hope that it will be useful,
      but WITHOUT ANY WARRANTY; without even the implied warranty of
      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      GNU General Public License for more details.
  
      You should have received a copy of the GNU General Public License
      along with this program; if not, write to the Free Software
      Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
      MA 02110-1301 USA.
  */
  
  #include &lt;errno.h&gt;
  #include &lt;i2c/smbus.h&gt;
  #include &lt;sys/ioctl.h&gt;
  #include &lt;linux/types.h&gt;
  #include &lt;linux/i2c.h&gt;
  #include &lt;linux/i2c-dev.h&gt;
  #include &quot;smbus.h&quot;
  #define NULL 0
  
  /* Compatibility defines */
  #ifndef I2C_SMBUS_I2C_BLOCK_BROKEN
  #define I2C_SMBUS_I2C_BLOCK_BROKEN I2C_SMBUS_I2C_BLOCK_DATA
  #endif
  #ifndef I2C_FUNC_SMBUS_PEC
  #define I2C_FUNC_SMBUS_PEC I2C_FUNC_SMBUS_HWPEC_CALC
  #endif
  
  __s32 i2c_smbus_access(int file, char read_write, __u8 command,
             int size, union i2c_smbus_data *data)
  {
      struct i2c_smbus_ioctl_data args;
      __s32 err;
  
      args.read_write = read_write;
      args.command = command;
      args.size = size;
      args.data = data;
  
      err = ioctl(file, I2C_SMBUS, &amp;args);
      if (err == -1)
          err = -errno;
      return err;
  }
  
  
  __s32 i2c_smbus_write_quick(int file, __u8 value)
  {
      return i2c_smbus_access(file, value, 0, I2C_SMBUS_QUICK, NULL);
  }
  
  __s32 i2c_smbus_read_byte(int file)
  {
      union i2c_smbus_data data;
      int err;
  
      err = i2c_smbus_access(file, I2C_SMBUS_READ, 0, I2C_SMBUS_BYTE, &amp;data);
      if (err &lt; 0)
          return err;
  
      return 0x0FF &amp; data.byte;
  }
  
  __s32 i2c_smbus_write_byte(int file, __u8 value)
  {
      return i2c_smbus_access(file, I2C_SMBUS_WRITE, value,
                  I2C_SMBUS_BYTE, NULL);
  }
  
  __s32 i2c_smbus_read_byte_data(int file, __u8 command)
  {
      union i2c_smbus_data data;
      int err;
  
      err = i2c_smbus_access(file, I2C_SMBUS_READ, command,
                     I2C_SMBUS_BYTE_DATA, &amp;data);
      if (err &lt; 0)
          return err;
  
      return 0x0FF &amp; data.byte;
  }
  
  __s32 i2c_smbus_write_byte_data(int file, __u8 command, __u8 value)
  {
      union i2c_smbus_data data;
      data.byte = value;
      return i2c_smbus_access(file, I2C_SMBUS_WRITE, command,
                  I2C_SMBUS_BYTE_DATA, &amp;data);
  }
  
  __s32 i2c_smbus_read_word_data(int file, __u8 command)
  {
      union i2c_smbus_data data;
      int err;
  
      err = i2c_smbus_access(file, I2C_SMBUS_READ, command,
                     I2C_SMBUS_WORD_DATA, &amp;data);
      if (err &lt; 0)
          return err;
  
      return 0x0FFFF &amp; data.word;
  }
  
  __s32 i2c_smbus_write_word_data(int file, __u8 command, __u16 value)
  {
      union i2c_smbus_data data;
      data.word = value;
      return i2c_smbus_access(file, I2C_SMBUS_WRITE, command,
                  I2C_SMBUS_WORD_DATA, &amp;data);
  }
  
  __s32 i2c_smbus_process_call(int file, __u8 command, __u16 value)
  {
      union i2c_smbus_data data;
      data.word = value;
      if (i2c_smbus_access(file, I2C_SMBUS_WRITE, command,
                   I2C_SMBUS_PROC_CALL, &amp;data))
          return -1;
      else
          return 0x0FFFF &amp; data.word;
  }
  
  /* Returns the number of read bytes */
  __s32 i2c_smbus_read_block_data(int file, __u8 command, __u8 *values)
  {
      union i2c_smbus_data data;
      int i, err;
  
      err = i2c_smbus_access(file, I2C_SMBUS_READ, command,
                     I2C_SMBUS_BLOCK_DATA, &amp;data);
      if (err &lt; 0)
          return err;
  
      for (i = 1; i &lt;= data.block[0]; i++)
          values[i-1] = data.block[i];
      return data.block[0];
  }
  
  __s32 i2c_smbus_write_block_data(int file, __u8 command, __u8 length,
                   const __u8 *values)
  {
      union i2c_smbus_data data;
      int i;
      if (length &gt; I2C_SMBUS_BLOCK_MAX)
          length = I2C_SMBUS_BLOCK_MAX;
      for (i = 1; i &lt;= length; i++)
          data.block[i] = values[i-1];
      data.block[0] = length;
      return i2c_smbus_access(file, I2C_SMBUS_WRITE, command,
                  I2C_SMBUS_BLOCK_DATA, &amp;data);
  }
  
  /* Returns the number of read bytes */
  /* Until kernel 2.6.22, the length is hardcoded to 32 bytes. If you
     ask for less than 32 bytes, your code will only work with kernels
     2.6.23 and later. */
  __s32 i2c_smbus_read_i2c_block_data(int file, __u8 command, __u8 length,
                      __u8 *values)
  {
      union i2c_smbus_data data;
      int i, err;
  
      if (length &gt; I2C_SMBUS_BLOCK_MAX)
          length = I2C_SMBUS_BLOCK_MAX;
      data.block[0] = length;
  
      err = i2c_smbus_access(file, I2C_SMBUS_READ, command,
                     length == 32 ? I2C_SMBUS_I2C_BLOCK_BROKEN :
                  I2C_SMBUS_I2C_BLOCK_DATA, &amp;data);
      if (err &lt; 0)
          return err;
  
      for (i = 1; i &lt;= data.block[0]; i++)
          values[i-1] = data.block[i];
      return data.block[0];
  }
  
  __s32 i2c_smbus_write_i2c_block_data(int file, __u8 command, __u8 length,
                       const __u8 *values)
  {
      union i2c_smbus_data data;
      int i;
      if (length &gt; I2C_SMBUS_BLOCK_MAX)
          length = I2C_SMBUS_BLOCK_MAX;
      for (i = 1; i &lt;= length; i++)
          data.block[i] = values[i-1];
      data.block[0] = length;
      return i2c_smbus_access(file, I2C_SMBUS_WRITE, command,
                  I2C_SMBUS_I2C_BLOCK_BROKEN, &amp;data);
  }
  
  /* Returns the number of read bytes */
  __s32 i2c_smbus_block_process_call(int file, __u8 command, __u8 length,
                     __u8 *values)
  {
      union i2c_smbus_data data;
      int i, err;
  
      if (length &gt; I2C_SMBUS_BLOCK_MAX)
          length = I2C_SMBUS_BLOCK_MAX;
      for (i = 1; i &lt;= length; i++)
          data.block[i] = values[i-1];
      data.block[0] = length;
  
      err = i2c_smbus_access(file, I2C_SMBUS_WRITE, command,
                     I2C_SMBUS_BLOCK_PROC_CALL, &amp;data);
      if (err &lt; 0)
          return err;
  
      for (i = 1; i &lt;= data.block[0]; i++)
          values[i-1] = data.block[i];
      return data.block[0];
  }
  </code></pre>
  <p><strong>smbus.h</strong></p>
  <pre><code>/*
      smbus.h - SMBus level access helper functions
  
      Copyright (C) 1995-97 Simon G. Vogl
      Copyright (C) 1998-99 Frodo Looijaard &lt;frodol@dds.nl&gt;
      Copyright (C) 2012-2013 Donovan Roudabush &lt;sharksfan98@gmail.com&gt;
  
      This program is free software; you can redistribute it and/or modify
      it under the terms of the GNU General Public License as published by
      the Free Software Foundation; either version 2 of the License, or
      (at your option) any later version.
  
      This program is distributed in the hope that it will be useful,
      but WITHOUT ANY WARRANTY; without even the implied warranty of
      MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
      GNU General Public License for more details.
      
      This software has been distrobuted for the Gryphon 7i series,
      maintained Jan 2013 by Donovan Roudabush at The Ballon Project
      This falls under GPL and Copyleft, but is intended for
      Research use.
  
      You should have received a copy of the GNU General Public License
      along with this program; if not, write to the Free Software
      Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston,
      MA 02110-1301 USA.
      
  */
  
  #ifndef LIB_I2C_SMBUS_H
  #define LIB_I2C_SMBUS_H
  
  #include &lt;linux/types.h&gt;
  #include &lt;linux/i2c.h&gt;
  
  extern __s32 i2c_smbus_access(int file, char read_write, __u8 command,
                int size, union i2c_smbus_data *data);
  
  extern __s32 i2c_smbus_write_quick(int file, __u8 value);
  extern __s32 i2c_smbus_read_byte(int file);
  extern __s32 i2c_smbus_write_byte(int file, __u8 value);
  extern __s32 i2c_smbus_read_byte_data(int file, __u8 command);
  extern __s32 i2c_smbus_write_byte_data(int file, __u8 command, __u8 value);
  extern __s32 i2c_smbus_read_word_data(int file, __u8 command);
  extern __s32 i2c_smbus_write_word_data(int file, __u8 command, __u16 value);
  extern __s32 i2c_smbus_process_call(int file, __u8 command, __u16 value);
  
  /* Returns the number of read bytes */
  extern __s32 i2c_smbus_read_block_data(int file, __u8 command, __u8 *values);
  extern __s32 i2c_smbus_write_block_data(int file, __u8 command, __u8 length,
                      const __u8 *values);
  
  /* Returns the number of read bytes */
  /* Until kernel 2.6.22, the length is hardcoded to 32 bytes. If you
     ask for less than 32 bytes, your code will only work with kernels
     2.6.23 and later. */
  extern __s32 i2c_smbus_read_i2c_block_data(int file, __u8 command, __u8 length,
                         __u8 *values);
  extern __s32 i2c_smbus_write_i2c_block_data(int file, __u8 command, __u8 length,
                          const __u8 *values);
  
  /* Returns the number of read bytes */
  extern __s32 i2c_smbus_block_process_call(int file, __u8 command, __u8 length,
                        __u8 *values);
  
  #endif /* LIB_I2C_SMBUS_H */
  </code></pre>
  <p><strong>altitude_ai.c</strong></p>
  <pre><code>#include &lt;stdio.h&gt;
  #include &lt;stdint.h&gt;
  #include &lt;fcntl.h&gt;
  #include &lt;stdlib.h&gt;
  
  #include &lt;unistd.h&gt;
  #include &lt;linux/i2c-dev.h&gt;
  #include &lt;linux/i2c.h&gt;
  #include &lt;sys/ioctl.h&gt;
  #include &quot;smbus.h&quot; 
  
  #define BMP085_I2C_ADDRESS 0x77
  
  const unsigned char BMP085_OVERSAMPLING_SETTING = 3;
  
  // Calibration values - These are stored in the BMP085
  short int ac1;
  short int ac2; 
  short int ac3; 
  unsigned short int ac4;
  unsigned short int ac5;
  unsigned short int ac6;
  short int b1; 
  short int b2;
  short int mb;
  short int mc;
  short int md;
  
  int b5; 
  
  unsigned int temperature, pressure, altitude;
  
  
  // Open a connection to the bmp085
  // Returns a file id
  int bmp085_i2c_Begin()
  {
     int fd;
     char *fileName = &quot;/dev/i2c-0&quot;;
     
     // Open port for reading and writing
     if ((fd = open(fileName, O_RDWR)) &lt; 0)
        exit(1);
     
     // Set the port options and set the address of the device
     if (ioctl(fd, I2C_SLAVE, BMP085_I2C_ADDRESS) &lt; 0) {               
        close(fd);
        exit(1);
     }
  
     return fd;
  }
  
  // Read two words from the BMP085 and supply it as a 16 bit integer
  __s32 bmp085_i2c_Read_Int(int fd, __u8 address)
  {
     __s32 res = i2c_smbus_read_word_data(fd, address);
     if (res &lt; 0) {
        close(fd);
        exit(1);
     }
  
     // Convert result to 16 bits and swap bytes
     res = ((res&lt;&lt;8) &amp; 0xFF00) | ((res&gt;&gt;8) &amp; 0xFF);
  
     return res;
  }
  
  //Write a byte to the BMP085
  void bmp085_i2c_Write_Byte(int fd, __u8 address, __u8 value)
  {
     if (i2c_smbus_write_byte_data(fd, address, value) &lt; 0) {
        close(fd);
        exit(1);
     }
  }
  
  // Read a block of data BMP085
  void bmp085_i2c_Read_Block(int fd, __u8 address, __u8 length, __u8 *values)
  {
     if(i2c_smbus_read_i2c_block_data(fd, address,length,values)&lt;0) {
        close(fd);
        exit(1);
     }
  }
  
  
  void bmp085_Calibration()
  {
     int fd = bmp085_i2c_Begin();
     ac1 = bmp085_i2c_Read_Int(fd,0xAA);
     ac2 = bmp085_i2c_Read_Int(fd,0xAC);
     ac3 = bmp085_i2c_Read_Int(fd,0xAE);
     ac4 = bmp085_i2c_Read_Int(fd,0xB0);
     ac5 = bmp085_i2c_Read_Int(fd,0xB2);
     ac6 = bmp085_i2c_Read_Int(fd,0xB4);
     b1 = bmp085_i2c_Read_Int(fd,0xB6);
     b2 = bmp085_i2c_Read_Int(fd,0xB8);
     mb = bmp085_i2c_Read_Int(fd,0xBA);
     mc = bmp085_i2c_Read_Int(fd,0xBC);
     md = bmp085_i2c_Read_Int(fd,0xBE);
     close(fd);
  }
  
  // Read the uncompensated temperature value
  unsigned int bmp085_ReadUT()
  {
     unsigned int ut = 0;
     int fd = bmp085_i2c_Begin();
  
     // Write 0x2E into Register 0xF4
     // This requests a temperature reading
     bmp085_i2c_Write_Byte(fd,0xF4,0x2E);
     
     // Wait at least 4.5ms
     usleep(5000);
  
     // Read the two byte result from address 0xF6
     ut = bmp085_i2c_Read_Int(fd,0xF6);
  
     // Close the i2c file
     close (fd);
     
     return ut;
  }
  
  // Read the uncompensated pressure value
  unsigned int bmp085_ReadUP()
  {
     unsigned int up = 0;
     int fd = bmp085_i2c_Begin();
  
     // Write 0x34+(BMP085_OVERSAMPLING_SETTING&lt;&lt;6) into register 0xF4
     // Request a pressure reading w/ oversampling setting
     bmp085_i2c_Write_Byte(fd,0xF4,0x34 + (BMP085_OVERSAMPLING_SETTING&lt;&lt;6));
  
     // Wait for conversion, delay time dependent on oversampling setting
     usleep((2 + (3&lt;&lt;BMP085_OVERSAMPLING_SETTING)) * 1000);
  
     // Read the three byte result from 0xF6
     // 0xF6 = MSB, 0xF7 = LSB and 0xF8 = XLSB
     __u8 values[3];
     bmp085_i2c_Read_Block(fd, 0xF6, 3, values);
  
     up = (((unsigned int) values[0] &lt;&lt; 16) | ((unsigned int) values[1] &lt;&lt; 8) | (unsigned int) values[2]) &gt;&gt; (8-BMP085_OVERSAMPLING_SETTING);
  
     return up;
  }
  
  // Calculate pressure given uncalibrated pressure
  // Value returned will be in units of XXXXX
  unsigned int bmp085_GetPressure(unsigned int up)
  {
     int x1, x2, x3, b3, b6, p;
     unsigned int b4, b7;
    
     b6 = b5 - 4000;
     // Calculate B3
     x1 = (b2 * (b6 * b6)&gt;&gt;12)&gt;&gt;11;
     x2 = (ac2 * b6)&gt;&gt;11;
     x3 = x1 + x2;
     b3 = (((((int)ac1)*4 + x3)&lt;&lt;BMP085_OVERSAMPLING_SETTING) + 2)&gt;&gt;2;
    
     // Calculate B4
     x1 = (ac3 * b6)&gt;&gt;13;
     x2 = (b1 * ((b6 * b6)&gt;&gt;12))&gt;&gt;16;
     x3 = ((x1 + x2) + 2)&gt;&gt;2;
     b4 = (ac4 * (unsigned int)(x3 + 32768))&gt;&gt;15;
    
     b7 = ((unsigned int)(up - b3) * (50000&gt;&gt;BMP085_OVERSAMPLING_SETTING));
     if (b7 &lt; 0x80000000)
        p = (b7&lt;&lt;1)/b4;
     else
        p = (b7/b4)&lt;&lt;1;
     
     x1 = (p&gt;&gt;8) * (p&gt;&gt;8);
     x1 = (x1 * 3038)&gt;&gt;16;
     x2 = (-7357 * p)&gt;&gt;16;
     p += (x1 + x2 + 3791)&gt;&gt;4;
    
     return p;
  }
  
  // Calculate temperature given uncalibrated temperature
  // Value returned will be in units of 0.1 deg C
  unsigned int bmp085_GetTemperature(unsigned int ut)
  {
     int x1, x2;
    
     x1 = (((int)ut - (int)ac6)*(int)ac5) &gt;&gt; 15;
     x2 = ((int)mc &lt;&lt; 11)/(x1 + md);
     b5 = x1 + x2;
  
     unsigned int result = ((b5 + 8)&gt;&gt;4);  
  
     return result;
  }
  
  // This Altitude part is stolen from some some unknown
  // Arduino library.  The number divided into pressure for
  // float A is derived from the local pressure as explained
  // at http://learn.adafruit.com/bmp085/using-the-bmp085.
  unsigned int bmp085_Altitude(float pressure)
  {
     float A = pressure/101794.58;
     float B = 1/5.25588;
     float C = pow(A,B);
     C = 1 - C;
     C = C / 0.0000225577;
  
     return C;
  }
  
  int main(int argc, char **argv)
  
  {
  
     bmp085_Calibration();
  
     temperature = bmp085_GetTemperature(bmp085_ReadUT());
     pressure = bmp085_GetPressure(bmp085_ReadUP());
          altitude = bmp085_Altitude(pressure);
  
     printf(&quot;Temperature\t%0.1f *F\n&quot;, ((double)temperature)/10 * 1.8 + 32);
     printf(&quot;Pressure\t%0.2f hPa\n&quot;, ((double)pressure)/100);
          printf(&quot;Altitude\t%0.1f Feet\n\n&quot;, ((double)altitude)*3.280839895);
  
     return 0;
  }
  </code></pre>
  <p>Can you guys help me fix the error message? Thank you in advance~</p>