drivers/ds1722.c

   1
   2 #include <common.h>
   3
   4 #include <ssi.h>
   5
   6 #ifdef CONFIG_DS1722
   7
   8 static void ds1722_select(int dev)
   9 {
  10         ssi_set_interface(4096, 0, 0, 0);
  11         ssi_chip_select(0);
  12         udelay(1);
  13         ssi_chip_select(dev);
  14         udelay(1);
  15 }
  16
  17
  18 u8 ds1722_read(int dev, int addr)
  19 {
  20         u8 res;
  21
  22         ds1722_select(dev);
  23
  24         ssi_tx_byte(addr);
  25         res = ssi_rx_byte();
  26
  27         ssi_chip_select(0);
  28
  29         return res;
  30 }
  31
  32 void ds1722_write(int dev, int addr, u8 data)
  33 {
  34         ds1722_select(dev);
  35
  36         ssi_tx_byte(0x80|addr);
  37         ssi_tx_byte(data);
  38
  39         ssi_chip_select(0);
  40 }
  41
  42
  43 u16 ds1722_temp(int dev, int resolution)
  44 {
  45         static int useconds[] = {
  46                 75000, 150000, 300000, 600000, 1200000
  47         };
  48         char temp;
  49         u16 res;
  50
  51
  52         /* set up the desired resulotion ... */
  53         ds1722_write(dev, 0, 0xe0 | (resolution << 1));
  54
  55         /* wait while the chip measures the tremperature */
  56         udelay(useconds[resolution]);
  57
  58         res = (temp = ds1722_read(dev, 2)) << 8;
  59
  60         if (temp < 0) {
  61                 temp = (16 - (ds1722_read(dev, 1) >> 4)) & 0x0f;
  62         } else {
  63                 temp = (ds1722_read(dev, 1) >> 4);
  64         }
  65
  66         switch (temp) {
  67         case 0:
  68                 /* .0000 */
  69                 break;
  70         case 1:
  71                 /* .0625 */
  72                 res |=1;
  73                 break;
  74         case 2:
  75                 /* .1250 */
  76                 res |=1;
  77                 break;
  78         case 3:
  79                 /* .1875 */
  80                 res |=2;
  81                 break;
  82         case 4:
  83                 /* .2500 */
  84                 res |=3;
  85                 break;
  86         case 5:
  87                 /* .3125 */
  88                 res |=3;
  89                 break;
  90         case 6:
  91                 /* .3750 */
  92                 res |=4;
  93                 break;
  94         case 7:
  95                 /* .4375 */
  96                 res |=4;
  97                 break;
  98         case 8:
  99                 /* .5000 */
 100                 res |=5;
 101                 break;
 102         case 9:
 103                 /* .5625 */
 104                 res |=6;
 105                 break;
 106         case 10:
 107                 /* .6250 */
 108                 res |=6;
 109                 break;
 110         case 11:
 111                 /* .6875 */
 112                 res |=7;
 113                 break;
 114         case 12:
 115                 /* .7500 */
 116                 res |=8;
 117                 break;
 118         case 13:
 119                 /* .8125 */
 120                 res |=8;
 121                 break;
 122         case 14:
 123                 /* .8750 */
 124                 res |=9;
 125                 break;
 126         case 15:
 127                 /* .9375 */
 128                 res |=9;
 129                 break;
 130         }
 131         return res;
 132
 133 }
 134
 135 int ds1722_probe(int dev)
 136 {
 137         u16 temp = ds1722_temp(dev, DS1722_RESOLUTION_12BIT);
 138         printf("%d.%d deg C\n\n", (char)(temp >> 8), temp & 0xff);
 139         return 0;
 140 }
 141
 142 #endif