firmware/target/arm/i2c-telechips.c

   1 /***************************************************************************
   2  *             __________               __   ___.
   3  *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
   4  *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
   5  *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
   6  *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
   7  *                     \/            \/     \/    \/            \/
   8  * $Id$
   9  *
  10  * Copyright (C) 2008 by Rob Purchase
  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 "config.h"
  20
  21 #include "system.h"
  22 #include "i2c.h"
  23 #include "i2c-target.h"
  24
  25 /* arbitrary delay loop */
  26 #define DELAY  do { int _x; for(_x=0;_x<40;_x++);} while (0)
  27
  28 static struct mutex i2c_mtx;
  29
  30 void i2c_init(void)
  31 {
  32     /* nothing to do */
  33 }
  34
  35 void i2c_start(void)
  36 {
  37     SDA_OUTPUT;
  38
  39     SCL_HI;
  40     SDA_HI;
  41     DELAY;
  42
  43     SDA_LO;
  44     DELAY;
  45     SCL_LO;
  46     DELAY;
  47 }
  48
  49 void i2c_stop(void)
  50 {
  51     SDA_OUTPUT;
  52
  53     SDA_LO;
  54     DELAY;
  55
  56     SCL_HI;
  57     DELAY;
  58     SDA_HI;
  59     DELAY;
  60 }
  61
  62 void i2c_outb(unsigned char byte)
  63 {
  64     int bit;
  65
  66     SDA_OUTPUT;
  67
  68     for (bit = 0; bit < 8; bit++)
  69     {
  70         if ((byte<<bit) & 0x80)
  71           SDA_HI;
  72         else
  73           SDA_LO;
  74
  75         DELAY;
  76
  77         SCL_HI;
  78         DELAY;
  79         SCL_LO;
  80         DELAY;
  81     }
  82 }
  83
  84 unsigned char i2c_inb(int ack)
  85 {
  86     int i;
  87     unsigned char byte = 0;
  88
  89     SDA_INPUT;
  90
  91     /* clock in each bit, MSB first */
  92     for ( i=0x80; i; i>>=1 )
  93     {
  94         SCL_HI;
  95         DELAY;
  96
  97         if ( SDA ) byte |= i;
  98
  99         SCL_LO;
 100         DELAY;
 101     }
 102
 103     i2c_ack(ack);
 104     return byte;
 105 }
 106
 107 void i2c_ack(int bit)
 108 {
 109     SDA_OUTPUT;
 110
 111     if (bit)
 112       SDA_HI;
 113     else
 114       SDA_LO;
 115
 116     SCL_HI;
 117     DELAY;
 118     SCL_LO;
 119     DELAY;
 120 }
 121
 122 int i2c_getack(void)
 123 {
 124     bool ack_bit;
 125
 126     SDA_INPUT;
 127
 128     SCL_HI;
 129     DELAY;
 130
 131     ack_bit = SDA;
 132     DELAY;
 133
 134     SCL_LO;
 135     DELAY;
 136
 137     return ack_bit;
 138 }
 139
 140 /* device = 8 bit slave address */
 141 int i2c_write(int device, const unsigned char* buf, int count )
 142 {
 143     int i = 0;
 144     mutex_lock(&i2c_mtx);
 145
 146     i2c_start();
 147     i2c_outb(device & 0xfe);
 148
 149     while (!i2c_getack() && i < count)
 150     {
 151         i2c_outb(buf[i++]);
 152     }
 153
 154     i2c_stop();
 155     mutex_unlock(&i2c_mtx);
 156     return 0;
 157 }
 158
 159
 160 /* device = 8 bit slave address */
 161 int i2c_readmem(int device, int address, unsigned char* buf, int count )
 162 {
 163     int i = 0;
 164     mutex_lock(&i2c_mtx);
 165
 166     i2c_start();
 167     i2c_outb(device & 0xfe);
 168     if (i2c_getack()) goto exit;
 169
 170     i2c_outb(address);
 171     if (i2c_getack()) goto exit;
 172
 173     i2c_start();
 174     i2c_outb(device | 1);
 175     if (i2c_getack()) goto exit;
 176
 177     while (i < count)
 178     {
 179         buf[i] = i2c_inb(i == (count-1));
 180         i++;
 181     }
 182
 183 exit:
 184     i2c_stop();
 185     mutex_unlock(&i2c_mtx);
 186     return 0;
 187 }