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 <msp430.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_APP,
  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 I2CDELAY(x) delay(x<<4)
  47
  48
  49 //2xx only, need 1xx compat code
  50 #if (board == tilaunchpad)
  51 // P3.1 SDA
  52 // P3.3 SCL
  53 #define SDA (1<<1)
  54 #define SCL (1<<3)
  55
  56 #define CLRSDA P3OUT&=~SDA
  57 #define SETSDA P3OUT|=SDA
  58 #define CLRSCL P3OUT&=~SCL
  59 #define SETSCL P3OUT|=SCL
  60
  61 #define READSDA (P3IN&SDA?1:0)
  62 #define SDAINPUT P3DIR&=~SDA
  63 #define SDAOUTPUT P3DIR|=SDA
  64 #define SCLINPUT P3DIR&=~SCL
  65 #define SCLOUTPUT P3DIR|=SCL
  66 #define SETBOTH P3OUT|=(SDA|SCL)
  67
  68 #else
  69
  70 #define SDA TDI
  71 #define SCL TDO
  72
  73 #define CLRSDA P5OUT&=~SDA
  74 #define SETSDA P5OUT|=SDA
  75 #define CLRSCL P5OUT&=~SCL
  76 #define SETSCL P5OUT|=SCL
  77
  78 #define READSDA (P5IN&SDA?1:0)
  79 #define SETBOTH P5OUT|=(SDA|SCL)
  80 #endif
  81
  82 #define I2C_DATA_HI() SETSDA
  83 #define I2C_DATA_LO() CLRSDA
  84
  85 #define I2C_CLOCK_HI() SETSCL
  86 #define I2C_CLOCK_LO() CLRSCL
  87
  88 //#warning "Using internal resistors.  Won't work on 161x devices."
  89
  90 //! Inits bitbanging port, must be called before using the functions below
  91 void I2C_Init()
  92 {
  93
  94   //Clear SDA and SCL.
  95   //Direction, not value, is used to set the value.
  96   //(Pull-up or 0.)
  97
  98 #if (platform == tilaunchpad)
  99   SDAOUTPUT;
 100   SCLOUTPUT;
 101 #else
 102   P5DIR|=(SDA|SCL);
 103 #endif
 104   //P5REN|=SDA|SCL;
 105
 106
 107   I2C_CLOCK_HI();
 108   I2C_DATA_HI();
 109
 110   I2CDELAY(1);
 111 }
 112
 113 #if (platform == tilaunchpad)
 114 void I2C_Exit()
 115 {
 116   SDAINPUT;
 117   SCLINPUT;
 118 }
 119 #endif
 120
 121 //! Write an I2C bit.
 122 void I2C_WriteBit( unsigned char c )
 123 {
 124   if(c>0)
 125     I2C_DATA_HI();
 126   else
 127     I2C_DATA_LO();
 128
 129   I2C_CLOCK_HI();
 130   I2CDELAY(1);
 131
 132   I2C_CLOCK_LO();
 133   I2CDELAY(1);
 134
 135   if(c>0)
 136     I2C_DATA_LO();
 137
 138   I2CDELAY(1);
 139 }
 140
 141 //! Read an I2C bit.
 142 unsigned char I2C_ReadBit()
 143 {
 144   I2C_DATA_HI();
 145
 146   I2C_CLOCK_HI();
 147   SDAINPUT;
 148   I2CDELAY(1);
 149
 150   unsigned char c = READSDA;
 151
 152   I2C_CLOCK_LO();
 153   I2CDELAY(1);
 154   SDAOUTPUT;
 155
 156   return c;
 157 }
 158
 159
 160 //! Send a START Condition
 161 void I2C_Start()
 162 {
 163   // set both to high at the same time
 164   SETBOTH;
 165   I2CDELAY(1);
 166
 167   I2C_DATA_LO();
 168   I2CDELAY(1);
 169
 170   I2C_CLOCK_LO();
 171   I2CDELAY(1);
 172 }
 173
 174 //! Send a STOP Condition
 175 void I2C_Stop()
 176 {
 177   I2C_CLOCK_HI();
 178   I2CDELAY(1);
 179
 180   I2C_DATA_HI();
 181   I2CDELAY(1);
 182 }
 183
 184 //! write a byte to the I2C slave device
 185 unsigned char I2C_Write( unsigned char c )
 186 {
 187   char i;
 188   for (i=0;i<8;i++){
 189     I2C_WriteBit( c & 0x80 );
 190     c<<=1;
 191   }
 192
 193   return I2C_ReadBit();
 194 }
 195
 196
 197 //! read a byte from the I2C slave device
 198 unsigned char I2C_Read( unsigned char ack )
 199 {
 200   unsigned char res = 0;
 201   char i;
 202
 203   for (i=0;i<8;i++){
 204     res <<= 1;
 205     res |= I2C_ReadBit();
 206   }
 207
 208   if( ack > 0)
 209     I2C_WriteBit(0);
 210   else
 211     I2C_WriteBit(1);
 212
 213   I2CDELAY(1);
 214
 215   return res;
 216 }
 217
 218
 219 //! Handles an i2c command.
 220 void i2c_handle_fn( uint8_t const app,
 221                                         uint8_t const verb,
 222                                         uint32_t const len)
 223 {
 224         unsigned char i;
 225         unsigned long l;
 226         switch(verb)
 227         {
 228
 229         case PEEK:
 230                 break;
 231         case POKE:
 232                 break;
 233
 234         case READ:
 235                 l = len;
 236                 if(l > 0)                                       //optional parameter of length
 237                         l=cmddata[0];
 238                 if(!l)                                          //default value of 1
 239                         l=1;
 240                 for(i = 0; i < l; i++)
 241                         cmddata[i]=I2C_Read(1); //Always acknowledge
 242                 txdata(app,verb,l);
 243                 break;
 244         case WRITE:
 245                 cmddata[0]=0;
 246                 for(i=0;i<len;i++)
 247                         cmddata[0]+=I2C_Write(cmddata[i]);
 248                 txdata(app,verb,1);
 249                 break;
 250         case START:
 251                 I2C_Start();
 252                 txdata(app,verb,0);
 253                 break;
 254         case STOP:
 255                 I2C_Stop();
 256                 txdata(app,verb,0);
 257                 break;
 258         case SETUP:
 259                 I2C_Init();
 260                 txdata(app,verb,0);
 261                 break;
 262         }
 263 }