hw/ads7846.c

   1 /*
   2  * TI ADS7846 / TSC2046 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 "hw.h"
  11 #include "devices.h"
  12 #include "console.h"
  13
  14 struct ads7846_state_s {
  15     qemu_irq interrupt;
  16
  17     int input[8];
  18     int pressure;
  19     int noise;
  20
  21     int cycle;
  22     int output;
  23 };
  24
  25 /* Control-byte bitfields */
  26 #define CB_PD0          (1 << 0)
  27 #define CB_PD1          (1 << 1)
  28 #define CB_SER          (1 << 2)
  29 #define CB_MODE         (1 << 3)
  30 #define CB_A0           (1 << 4)
  31 #define CB_A1           (1 << 5)
  32 #define CB_A2           (1 << 6)
  33 #define CB_START        (1 << 7)
  34
  35 #define X_AXIS_DMAX     3470
  36 #define X_AXIS_MIN      290
  37 #define Y_AXIS_DMAX     3450
  38 #define Y_AXIS_MIN      200
  39
  40 #define ADS_VBAT        2000
  41 #define ADS_VAUX        2000
  42 #define ADS_TEMP0       2000
  43 #define ADS_TEMP1       3000
  44 #define ADS_XPOS(x, y)  (X_AXIS_MIN + ((X_AXIS_DMAX * (x)) >> 15))
  45 #define ADS_YPOS(x, y)  (Y_AXIS_MIN + ((Y_AXIS_DMAX * (y)) >> 15))
  46 #define ADS_Z1POS(x, y) 600
  47 #define ADS_Z2POS(x, y) (600 + 6000 / ADS_XPOS(x, y))
  48
  49 static void ads7846_int_update(struct ads7846_state_s *s)
  50 {
  51     if (s->interrupt)
  52         qemu_set_irq(s->interrupt, s->pressure == 0);
  53 }
  54
  55 uint32_t ads7846_read(void *opaque)
  56 {
  57     struct ads7846_state_s *s = (struct ads7846_state_s *) opaque;
  58
  59     return s->output;
  60 }
  61
  62 void ads7846_write(void *opaque, uint32_t value)
  63 {
  64     struct ads7846_state_s *s = (struct ads7846_state_s *) opaque;
  65
  66     switch (s->cycle ++) {
  67     case 0:
  68         if (!(value & CB_START)) {
  69             s->cycle = 0;
  70             break;
  71         }
  72
  73         s->output = s->input[(value >> 4) & 7];
  74
  75         /* Imitate the ADC noise, some drivers expect this.  */
  76         s->noise = (s->noise + 3) & 7;
  77         switch ((value >> 4) & 7) {
  78         case 1: s->output += s->noise ^ 2; break;
  79         case 3: s->output += s->noise ^ 0; break;
  80         case 4: s->output += s->noise ^ 7; break;
  81         case 5: s->output += s->noise ^ 5; break;
  82         }
  83
  84         if (value & CB_MODE)
  85             s->output >>= 4;    /* 8 bits instead of 12 */
  86
  87         break;
  88     case 1:
  89         s->cycle = 0;
  90         break;
  91     }
  92 }
  93
  94 static void ads7846_ts_event(void *opaque,
  95                 int x, int y, int z, int buttons_state)
  96 {
  97     struct ads7846_state_s *s = opaque;
  98
  99     if (buttons_state) {
 100         x = 0x7fff - x;
 101         s->input[1] = ADS_XPOS(x, y);
 102         s->input[3] = ADS_Z1POS(x, y);
 103         s->input[4] = ADS_Z2POS(x, y);
 104         s->input[5] = ADS_YPOS(x, y);
 105     }
 106
 107     if (s->pressure == !buttons_state) {
 108         s->pressure = !!buttons_state;
 109
 110         ads7846_int_update(s);
 111     }
 112 }
 113
 114 static void ads7846_save(QEMUFile *f, void *opaque)
 115 {
 116     struct ads7846_state_s *s = (struct ads7846_state_s *) opaque;
 117     int i;
 118
 119     for (i = 0; i < 8; i ++)
 120         qemu_put_be32(f, s->input[i]);
 121     qemu_put_be32(f, s->noise);
 122     qemu_put_be32(f, s->cycle);
 123     qemu_put_be32(f, s->output);
 124 }
 125
 126 static int ads7846_load(QEMUFile *f, void *opaque, int version_id)
 127 {
 128     struct ads7846_state_s *s = (struct ads7846_state_s *) opaque;
 129     int i;
 130
 131     for (i = 0; i < 8; i ++)
 132         s->input[i] = qemu_get_be32(f);
 133     s->noise = qemu_get_be32(f);
 134     s->cycle = qemu_get_be32(f);
 135     s->output = qemu_get_be32(f);
 136
 137     s->pressure = 0;
 138     ads7846_int_update(s);
 139
 140     return 0;
 141 }
 142
 143 static int ads7846_iid = 0;
 144
 145 struct ads7846_state_s *ads7846_init(qemu_irq penirq)
 146 {
 147     struct ads7846_state_s *s;
 148     s = (struct ads7846_state_s *)
 149             qemu_mallocz(sizeof(struct ads7846_state_s));
 150     memset(s, 0, sizeof(struct ads7846_state_s));
 151
 152     s->interrupt = penirq;
 153
 154     s->input[0] = ADS_TEMP0;    /* TEMP0 */
 155     s->input[2] = ADS_VBAT;     /* VBAT */
 156     s->input[6] = ADS_VAUX;     /* VAUX */
 157     s->input[7] = ADS_TEMP1;    /* TEMP1 */
 158
 159     /* We want absolute coordinates */
 160     qemu_add_mouse_event_handler(ads7846_ts_event, s, 1,
 161                     "QEMU ADS7846-driven Touchscreen");
 162
 163     ads7846_int_update(s);
 164
 165     register_savevm("ads7846", ads7846_iid ++, 0,
 166                     ads7846_save, ads7846_load, s);
 167
 168     return s;
 169 }