hw/ads7846.c

   1 /*
   2  * TI ADS7846 chip emulation.
   3  *
   4  * Copyright (c) 2006 Openedhand Ltd.
   5  * Written by Andrzej Zaborowski <balrog@zabor.org>
   6  *
   7  * This code is licensed under the GNU GPL v2.
   8  */
   9
  10 #include <vl.h>
  11
  12 struct ads7846_state_s {
  13     qemu_irq interrupt;
  14
  15     int input[8];
  16     int pressure;
  17     int noise;
  18
  19     int cycle;
  20     int output;
  21 };
  22
  23 /* Control-byte bitfields */
  24 #define CB_PD0          (1 << 0)
  25 #define CB_PD1          (1 << 1)
  26 #define CB_SER          (1 << 2)
  27 #define CB_MODE         (1 << 3)
  28 #define CB_A0           (1 << 4)
  29 #define CB_A1           (1 << 5)
  30 #define CB_A2           (1 << 6)
  31 #define CB_START        (1 << 7)
  32
  33 #define X_AXIS_DMAX     3680
  34 #define X_AXIS_MIN      150
  35 #define Y_AXIS_DMAX     3640
  36 #define Y_AXIS_MIN      190
  37
  38 #define ADS_VBAT        2000
  39 #define ADS_VAUX        2000
  40 #define ADS_TEMP0       2000
  41 #define ADS_TEMP1       3000
  42 #define ADS_XPOS(x, y)  (X_AXIS_MIN + ((X_AXIS_DMAX * (x)) >> 15))
  43 #define ADS_YPOS(x, y)  (Y_AXIS_MIN + ((Y_AXIS_DMAX * (y)) >> 15))
  44 #define ADS_Z1POS(x, y) 600
  45 #define ADS_Z2POS(x, y) (600 + 6000 / ADS_XPOS(x, y))
  46
  47 static void ads7846_int_update(struct ads7846_state_s *s)
  48 {
  49     if (s->interrupt)
  50         qemu_set_irq(s->interrupt, s->pressure == 0);
  51 }
  52
  53 uint32_t ads7846_read(void *opaque)
  54 {
  55     struct ads7846_state_s *s = (struct ads7846_state_s *) opaque;
  56
  57     return s->output;
  58 }
  59
  60 void ads7846_write(void *opaque, uint32_t value)
  61 {
  62     struct ads7846_state_s *s = (struct ads7846_state_s *) opaque;
  63
  64     switch (s->cycle ++) {
  65     case 0:
  66         if (!(value & CB_START)) {
  67             s->cycle = 0;
  68             break;
  69         }
  70
  71         s->output = s->input[(value >> 4) & 7];
  72
  73         /* Imitate the ADC noise, some drivers expect this.  */
  74         s->noise = (s->noise + 3) & 7;
  75         switch ((value >> 4) & 7) {
  76         case 1: s->output += s->noise ^ 2; break;
  77         case 3: s->output += s->noise ^ 0; break;
  78         case 4: s->output += s->noise ^ 7; break;
  79         case 5: s->output += s->noise ^ 5; break;
  80         }
  81
  82         if (value & CB_MODE)
  83             s->output >>= 4;    /* 8 bits instead of 12 */
  84
  85         break;
  86     case 1:
  87         s->cycle = 0;
  88         break;
  89     }
  90 }
  91
  92 static void ads7846_ts_event(void *opaque,
  93                 int x, int y, int z, int buttons_state)
  94 {
  95     struct ads7846_state_s *s = opaque;
  96
  97     if (buttons_state) {
  98         s->input[1] = ADS_YPOS(x, y);
  99         s->input[3] = ADS_Z1POS(x, y);
 100         s->input[4] = ADS_Z2POS(x, y);
 101         s->input[5] = ADS_XPOS(x, y);
 102     }
 103
 104     if (s->pressure == !buttons_state) {
 105         s->pressure = !!buttons_state;
 106
 107         ads7846_int_update(s);
 108     }
 109 }
 110
 111 static void ads7846_save(QEMUFile *f, void *opaque)
 112 {
 113     struct ads7846_state_s *s = (struct ads7846_state_s *) opaque;
 114     int i;
 115
 116     for (i = 0; i < 8; i ++)
 117         qemu_put_be32(f, s->input[i]);
 118     qemu_put_be32(f, s->noise);
 119     qemu_put_be32(f, s->cycle);
 120     qemu_put_be32(f, s->output);
 121 }
 122
 123 static int ads7846_load(QEMUFile *f, void *opaque, int version_id)
 124 {
 125     struct ads7846_state_s *s = (struct ads7846_state_s *) opaque;
 126     int i;
 127
 128     for (i = 0; i < 8; i ++)
 129         s->input[i] = qemu_get_be32(f);
 130     s->noise = qemu_get_be32(f);
 131     s->cycle = qemu_get_be32(f);
 132     s->output = qemu_get_be32(f);
 133
 134     s->pressure = 0;
 135     ads7846_int_update(s);
 136
 137     return 0;
 138 }
 139
 140 static int ads7846_iid = 0;
 141
 142 struct ads7846_state_s *ads7846_init(qemu_irq penirq)
 143 {
 144     struct ads7846_state_s *s;
 145     s = (struct ads7846_state_s *)
 146             qemu_mallocz(sizeof(struct ads7846_state_s));
 147     memset(s, 0, sizeof(struct ads7846_state_s));
 148
 149     s->interrupt = penirq;
 150
 151     s->input[0] = ADS_TEMP0;    /* TEMP0 */
 152     s->input[2] = ADS_VBAT;     /* VBAT */
 153     s->input[6] = ADS_VAUX;     /* VAUX */
 154     s->input[7] = ADS_TEMP1;    /* TEMP1 */
 155
 156     /* We want absolute coordinates */
 157     qemu_add_mouse_event_handler(ads7846_ts_event, s, 1,
 158                     "QEMU ADS7846-driven Touchscreen");
 159
 160     ads7846_int_update(s);
 161
 162     register_savevm("ads7846", ads7846_iid ++, 0,
 163                     ads7846_save, ads7846_load, s);
 164
 165     return s;
 166 }