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 "ssi.h"
  11 #include "console.h"
  12
  13 typedef struct {
  14     SSISlave ssidev;
  15     qemu_irq interrupt;
  16
  17     int input[8];
  18     int pressure;
  19     int noise;
  20
  21     int cycle;
  22     int output;
  23 } ADS7846State;
  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(ADS7846State *s)
  50 {
  51     if (s->interrupt)
  52         qemu_set_irq(s->interrupt, s->pressure == 0);
  53 }
  54
  55 static uint32_t ads7846_transfer(SSISlave *dev, uint32_t value)
  56 {
  57     ADS7846State *s = FROM_SSI_SLAVE(ADS7846State, dev);
  58
  59     switch (s->cycle ++) {
  60     case 0:
  61         if (!(value & CB_START)) {
  62             s->cycle = 0;
  63             break;
  64         }
  65
  66         s->output = s->input[(value >> 4) & 7];
  67
  68         /* Imitate the ADC noise, some drivers expect this.  */
  69         s->noise = (s->noise + 3) & 7;
  70         switch ((value >> 4) & 7) {
  71         case 1: s->output += s->noise ^ 2; break;
  72         case 3: s->output += s->noise ^ 0; break;
  73         case 4: s->output += s->noise ^ 7; break;
  74         case 5: s->output += s->noise ^ 5; break;
  75         }
  76
  77         if (value & CB_MODE)
  78             s->output >>= 4;    /* 8 bits instead of 12 */
  79
  80         break;
  81     case 1:
  82         s->cycle = 0;
  83         break;
  84     }
  85     return s->output;
  86 }
  87
  88 static void ads7846_ts_event(void *opaque,
  89                 int x, int y, int z, int buttons_state)
  90 {
  91     ADS7846State *s = opaque;
  92
  93     if (buttons_state) {
  94         x = 0x7fff - x;
  95         s->input[1] = ADS_XPOS(x, y);
  96         s->input[3] = ADS_Z1POS(x, y);
  97         s->input[4] = ADS_Z2POS(x, y);
  98         s->input[5] = ADS_YPOS(x, y);
  99     }
 100
 101     if (s->pressure == !buttons_state) {
 102         s->pressure = !!buttons_state;
 103
 104         ads7846_int_update(s);
 105     }
 106 }
 107
 108 static int ads7856_post_load(void *opaque, int version_id)
 109 {
 110     ADS7846State *s = opaque;
 111
 112     s->pressure = 0;
 113     ads7846_int_update(s);
 114     return 0;
 115 }
 116
 117 static const VMStateDescription vmstate_ads7846 = {
 118     .name = "ads7846",
 119     .version_id = 0,
 120     .minimum_version_id = 0,
 121     .minimum_version_id_old = 0,
 122     .post_load = ads7856_post_load,
 123     .fields      = (VMStateField[]) {
 124         VMSTATE_INT32_ARRAY(input, ADS7846State, 8),
 125         VMSTATE_INT32(noise, ADS7846State),
 126         VMSTATE_INT32(cycle, ADS7846State),
 127         VMSTATE_INT32(output, ADS7846State),
 128         VMSTATE_END_OF_LIST()
 129     }
 130 };
 131
 132 static int ads7846_init(SSISlave *dev)
 133 {
 134     ADS7846State *s = FROM_SSI_SLAVE(ADS7846State, dev);
 135
 136     qdev_init_gpio_out(&dev->qdev, &s->interrupt, 1);
 137
 138     s->input[0] = ADS_TEMP0;    /* TEMP0 */
 139     s->input[2] = ADS_VBAT;     /* VBAT */
 140     s->input[6] = ADS_VAUX;     /* VAUX */
 141     s->input[7] = ADS_TEMP1;    /* TEMP1 */
 142
 143     /* We want absolute coordinates */
 144     qemu_add_mouse_event_handler(ads7846_ts_event, s, 1,
 145                     "QEMU ADS7846-driven Touchscreen");
 146
 147     ads7846_int_update(s);
 148
 149     vmstate_register(NULL, -1, &vmstate_ads7846, s);
 150     return 0;
 151 }
 152
 153 static SSISlaveInfo ads7846_info = {
 154     .qdev.name ="ads7846",
 155     .qdev.size = sizeof(ADS7846State),
 156     .init = ads7846_init,
 157     .transfer = ads7846_transfer
 158 };
 159
 160 static void ads7846_register_devices(void)
 161 {
 162     ssi_register_slave(&ads7846_info);
 163 }
 164
 165 device_init(ads7846_register_devices)