git.rot13.org Git - goodfet/blob - firmware/apps/i2c/i2c.c

   1 /*! \file i2c.c
   2   \author Travis Goodspeed
   3   \brief I2C Master
   4 */
   5
   6
   7 //Higher level left to client application.
   8
   9 //Based upon a neighborly example at
  10 //http://codinglab.blogspot.com/2008/10/i2c-on-avr-using-bit-banging.html
  11
  12 #include "platform.h"
  13 #include "command.h"
  14 #include "i2c.h"
  15
  16 #include <signal.h>
  17 #include <io.h>
  18 #include <iomacros.h>
  19
  20
  21 //Pins and I/O
  22 #include <jtag.h>
  23
  24 //! Handles an i2c command.
  25 void i2c_handle_fn( uint8_t const app,
  26                                         uint8_t const verb,
  27                                         uint32_t const len);
  28
  29 // define the i2c app's app_t
  30 app_t const i2c_app = {
  31
  32         /* app number */
  33         I2C,
  34
  35         /* handle fn */
  36         i2c_handle_fn,
  37
  38         /* name */
  39         "I2C",
  40
  41         /* desc */
  42         "\tThe I2C app implements the i2c bus protocol thus\n"
  43         "\tturning your GoodFET into a USB-to-i2c adapter.\n"
  44 };
  45
  46 #define SDA TDI
  47 #define SCL TDO
  48
  49 #define I2CDELAY(x) delay(x<<4)
  50
  51
  52 //2xx only, need 1xx compat code
  53 #define CLRSDA P5OUT&=~SDA
  54 #define SETSDA P5OUT|=SDA
  55 #define CLRSCL P5OUT&=~SCL
  56 #define SETSCL P5OUT|=SCL
  57
  58 #define READSDA (P5IN&SDA?1:0)
  59 #define SETBOTH P5OUT|=(SDA|SCL)
  60
  61 #define I2C_DATA_HI() SETSDA
  62 #define I2C_DATA_LO() CLRSDA
  63
  64 #define I2C_CLOCK_HI() SETSCL
  65 #define I2C_CLOCK_LO() CLRSCL
  66
  67 //#warning "Using internal resistors.  Won't work on 161x devices."
  68
  69 //! Inits bitbanging port, must be called before using the functions below
  70 void I2C_Init()
  71 {
  72
  73   //Clear SDA and SCL.
  74   //Direction, not value, is used to set the value.
  75   //(Pull-up or 0.)
  76
  77   P5DIR|=(SDA|SCL);
  78   //P5REN|=SDA|SCL;
  79
  80
  81   I2C_CLOCK_HI();
  82   I2C_DATA_HI();
  83
  84   I2CDELAY(1);
  85 }
  86
  87 //! Write an I2C bit.
  88 void I2C_WriteBit( unsigned char c )
  89 {
  90   if(c>0)
  91     I2C_DATA_HI();
  92   else
  93     I2C_DATA_LO();
  94
  95   I2C_CLOCK_HI();
  96   I2CDELAY(1);
  97
  98   I2C_CLOCK_LO();
  99   I2CDELAY(1);
 100
 101   if(c>0)
 102     I2C_DATA_LO();
 103
 104   I2CDELAY(1);
 105 }
 106
 107 //! Read an I2C bit.
 108 unsigned char I2C_ReadBit()
 109 {
 110   I2C_DATA_HI();
 111
 112   I2C_CLOCK_HI();
 113   I2CDELAY(1);
 114
 115   unsigned char c = READSDA;
 116
 117   I2C_CLOCK_LO();
 118   I2CDELAY(1);
 119
 120   return c;
 121 }
 122
 123
 124 //! Send a START Condition
 125 void I2C_Start()
 126 {
 127   // set both to high at the same time
 128   SETBOTH;
 129   I2CDELAY(1);
 130
 131   I2C_DATA_LO();
 132   I2CDELAY(1);
 133
 134   I2C_CLOCK_LO();
 135   I2CDELAY(1);
 136 }
 137
 138 //! Send a STOP Condition
 139 void I2C_Stop()
 140 {
 141   I2C_CLOCK_HI();
 142   I2CDELAY(1);
 143
 144   I2C_DATA_HI();
 145   I2CDELAY(1);
 146 }
 147
 148 //! write a byte to the I2C slave device
 149 unsigned char I2C_Write( unsigned char c )
 150 {
 151   char i;
 152   for (i=0;i<8;i++){
 153     I2C_WriteBit( c & 0x80 );
 154     c<<=1;
 155   }
 156
 157   return I2C_ReadBit();
 158 }
 159
 160
 161 //! read a byte from the I2C slave device
 162 unsigned char I2C_Read( unsigned char ack )
 163 {
 164   unsigned char res = 0;
 165   char i;
 166
 167   for (i=0;i<8;i++){
 168     res <<= 1;
 169     res |= I2C_ReadBit();
 170   }
 171
 172   if( ack > 0)
 173     I2C_WriteBit(0);
 174   else
 175     I2C_WriteBit(1);
 176
 177   I2CDELAY(1);
 178
 179   return res;
 180 }
 181
 182
 183 //! Handles an i2c command.
 184 void i2c_handle_fn( uint8_t const app,
 185                                         uint8_t const verb,
 186                                         uint32_t const len)
 187 {
 188         unsigned char i;
 189         unsigned long l;
 190         switch(verb)
 191         {
 192
 193         case PEEK:
 194                 break;
 195         case POKE:
 196                 break;
 197
 198         case READ:
 199                 l = len;
 200                 if(l > 0)                                       //optional parameter of length
 201                         l=cmddata[0];
 202                 if(!l)                                          //default value of 1
 203                         l=1;
 204                 for(i = 0; i < l; i++)
 205                         cmddata[i]=I2C_Read(1); //Always acknowledge
 206                 txdata(app,verb,l);
 207                 break;
 208         case WRITE:
 209                 cmddata[0]=0;
 210                 for(i=0;i<len;i++)
 211                         cmddata[0]+=I2C_Write(cmddata[i]);
 212                 txdata(app,verb,1);
 213                 break;
 214         case START:
 215                 I2C_Start();
 216                 txdata(app,verb,0);
 217                 break;
 218         case STOP:
 219                 I2C_Stop();
 220                 txdata(app,verb,0);
 221                 break;
 222         case SETUP:
 223                 I2C_Init();
 224                 txdata(app,verb,0);
 225                 break;
 226         }
 227 }