firmware/drivers/i2c.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Copyright (C) 2002 by Linus Nielsen Feltzing
  11  *
  12  * All files in this archive are subject to the GNU General Public License.
  13  * See the file COPYING in the source tree root for full license agreement.
  14  *
  15  * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
  16  * KIND, either express or implied.
  17  *
  18  ****************************************************************************/
  19 #include "lcd.h"
  20 #include "cpu.h"
  21 #include "kernel.h"
  22 #include "thread.h"
  23 #include "debug.h"
  24 #include "system.h"
  25
  26 /* cute little functions, atomic read-modify-write */
  27
  28 /* SDA is PB7 */
  29 #define SDA_LO     and_b(~0x80, &PBDRL)
  30 #define SDA_HI     or_b(0x80, &PBDRL)
  31 #define SDA_INPUT  and_b(~0x80, &PBIORL)
  32 #define SDA_OUTPUT or_b(0x80, &PBIORL)
  33 #define SDA        (PBDRL & 0x80)
  34
  35 #if CONFIG_I2C == I2C_ONDIO
  36 /* Ondio pinout, SCL moved to PB6 */
  37 #define SCL_INPUT  and_b(~0x40, &PBIORL)
  38 #define SCL_OUTPUT or_b(0x40, &PBIORL)
  39 #define SCL_LO     and_b(~0x40, &PBDRL)
  40 #define SCL_HI     or_b(0x40, &PBDRL)
  41 #define SCL        (PBDRL & 0x40)
  42 #else
  43 /* "classic" pinout, SCL is PB13 */
  44 #define SCL_INPUT  and_b(~0x20, &PBIORH)
  45 #define SCL_OUTPUT or_b(0x20, &PBIORH)
  46 #define SCL_LO     and_b(~0x20, &PBDRH)
  47 #define SCL_HI     or_b(0x20, &PBDRH)
  48 #define SCL        (PBDRH & 0x20)
  49 #endif
  50
  51 /* arbitrary delay loop */
  52 #define DELAY   do { int _x; for(_x=0;_x<20;_x++);} while (0)
  53
  54 static struct mutex i2c_mtx;
  55
  56 void i2c_begin(void)
  57 {
  58     mutex_lock(&i2c_mtx);
  59 }
  60
  61 void i2c_end(void)
  62 {
  63     mutex_unlock(&i2c_mtx);
  64 }
  65
  66 void i2c_start(void)
  67 {
  68     SDA_OUTPUT;
  69     SDA_HI;
  70     SCL_HI;
  71     SDA_LO;
  72     DELAY;
  73     SCL_LO;
  74 }
  75
  76 void i2c_stop(void)
  77 {
  78    SDA_LO;
  79    SCL_HI;
  80    DELAY;
  81    SDA_HI;
  82 }
  83
  84 void i2c_init(void)
  85 {
  86    int i;
  87
  88 #if CONFIG_I2C == I2C_ONDIO
  89    /* make PB6 & PB7 general I/O */
  90    PBCR2 &= ~0xf000;
  91 #else /* not Ondio */
  92    /* make PB7 & PB13 general I/O */
  93    PBCR1 &= ~0x0c00; /* PB13 */
  94    PBCR2 &= ~0xc000; /* PB7 */
  95 #endif
  96
  97    SCL_OUTPUT;
  98    SDA_OUTPUT;
  99    SDA_HI;
 100    SCL_LO;
 101    for (i=0;i<3;i++)
 102       i2c_stop();
 103 }
 104
 105 void i2c_ack(int bit)
 106 {
 107     /* Here's the deal. The MAS is slow, and sometimes needs to wait
 108        before it can receive the acknowledge. Therefore it forces the clock
 109        low until it is ready. We need to poll the clock line until it goes
 110        high before we release the ack. */
 111
 112     SCL_LO;      /* Set the clock low */
 113     if ( bit )
 114     {
 115         SDA_HI;
 116     }
 117     else
 118     {
 119         SDA_LO;
 120     }
 121
 122     SCL_INPUT;   /* Set the clock to input */
 123     while(!SCL)  /* and wait for the MAS to release it */
 124         sleep_thread(1);
 125
 126     DELAY;
 127     SCL_OUTPUT;
 128     SCL_LO;
 129 }
 130
 131 int i2c_getack(void)
 132 {
 133     int ret = 1;
 134
 135     /* Here's the deal. The MAS is slow, and sometimes needs to wait
 136        before it can send the acknowledge. Therefore it forces the clock
 137        low until it is ready. We need to poll the clock line until it goes
 138        high before we read the ack. */
 139
 140 #ifdef HAVE_I2C_LOW_FIRST
 141     SDA_LO;      /* First, discharge the data line */
 142 #endif
 143     SDA_INPUT;   /* And set to input */
 144     SCL_INPUT;   /* Set the clock to input */
 145     while(!SCL)  /* and wait for the MAS to release it */
 146         sleep_thread(1);
 147
 148     if (SDA)
 149         /* ack failed */
 150         ret = 0;
 151
 152     SCL_OUTPUT;
 153     SCL_LO;
 154     SDA_HI;
 155     SDA_OUTPUT;
 156     return ret;
 157 }
 158
 159 void i2c_outb(unsigned char byte)
 160 {
 161    int i;
 162
 163    /* clock out each bit, MSB first */
 164    for ( i=0x80; i; i>>=1 ) {
 165       if ( i & byte )
 166       {
 167          SDA_HI;
 168       }
 169       else
 170       {
 171          SDA_LO;
 172       }
 173       SCL_HI;
 174       SCL_LO;
 175    }
 176
 177    SDA_HI;
 178 }
 179
 180 unsigned char i2c_inb(int ack)
 181 {
 182    int i;
 183    unsigned char byte = 0;
 184
 185    /* clock in each bit, MSB first */
 186    for ( i=0x80; i; i>>=1 ) {
 187 #ifdef HAVE_I2C_LOW_FIRST
 188        /* Tricky business. Here we discharge the data line by driving it low
 189           and then set it to input to see if it stays low or goes high */
 190        SDA_LO;      /* First, discharge the data line */
 191 #endif
 192        SDA_INPUT;   /* And set to input */
 193        SCL_HI;
 194        if ( SDA )
 195            byte |= i;
 196        SCL_LO;
 197        SDA_OUTPUT;
 198    }
 199
 200    i2c_ack(ack);
 201
 202    return byte;
 203 }
 204
 205 int i2c_write(int address, const unsigned char* buf, int count )
 206 {
 207     int i,x=0;
 208
 209     i2c_start();
 210     i2c_outb(address & 0xfe);
 211     if (i2c_getack())
 212     {
 213         for (i=0; i<count; i++)
 214         {
 215             i2c_outb(buf[i]);
 216             if (!i2c_getack())
 217             {
 218                 x=-2;
 219                 break;
 220             }
 221         }
 222     }
 223     else
 224     {
 225         debugf("i2c_write() - no ack\n");
 226         x=-1;
 227     }
 228     i2c_stop();
 229     return x;
 230 }
 231
 232 int i2c_read(int address, unsigned char* buf, int count )
 233 {
 234     int i,x=0;
 235
 236     i2c_start();
 237     i2c_outb(address | 1);
 238     if (i2c_getack()) {
 239         for (i=0; i<count; i++) {
 240             buf[i] = i2c_inb(0);
 241         }
 242     }
 243     else
 244         x=-1;
 245     i2c_stop();
 246     return x;
 247 }