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  * Contributions after 2012-01-13 are licensed under the terms of the
  10  * GNU GPL, version 2 or (at your option) any later version.
  11  */
  12
  13 #include "ssi.h"
  14 #include "console.h"
  15
  16 typedef struct {
  17     SSISlave ssidev;
  18     qemu_irq interrupt;
  19
  20     int input[8];
  21     int pressure;
  22     int noise;
  23
  24     int cycle;
  25     int output;
  26 } ADS7846State;
  27
  28 /* Control-byte bitfields */
  29 #define CB_PD0          (1 << 0)
  30 #define CB_PD1          (1 << 1)
  31 #define CB_SER          (1 << 2)
  32 #define CB_MODE         (1 << 3)
  33 #define CB_A0           (1 << 4)
  34 #define CB_A1           (1 << 5)
  35 #define CB_A2           (1 << 6)
  36 #define CB_START        (1 << 7)
  37
  38 #define X_AXIS_DMAX     3470
  39 #define X_AXIS_MIN      290
  40 #define Y_AXIS_DMAX     3450
  41 #define Y_AXIS_MIN      200
  42
  43 #define ADS_VBAT        2000
  44 #define ADS_VAUX        2000
  45 #define ADS_TEMP0       2000
  46 #define ADS_TEMP1       3000
  47 #define ADS_XPOS(x, y)  (X_AXIS_MIN + ((X_AXIS_DMAX * (x)) >> 15))
  48 #define ADS_YPOS(x, y)  (Y_AXIS_MIN + ((Y_AXIS_DMAX * (y)) >> 15))
  49 #define ADS_Z1POS(x, y) 600
  50 #define ADS_Z2POS(x, y) (600 + 6000 / ADS_XPOS(x, y))
  51
  52 static void ads7846_int_update(ADS7846State *s)
  53 {
  54     if (s->interrupt)
  55         qemu_set_irq(s->interrupt, s->pressure == 0);
  56 }
  57
  58 static uint32_t ads7846_transfer(SSISlave *dev, uint32_t value)
  59 {
  60     ADS7846State *s = FROM_SSI_SLAVE(ADS7846State, dev);
  61
  62     switch (s->cycle ++) {
  63     case 0:
  64         if (!(value & CB_START)) {
  65             s->cycle = 0;
  66             break;
  67         }
  68
  69         s->output = s->input[(value >> 4) & 7];
  70
  71         /* Imitate the ADC noise, some drivers expect this.  */
  72         s->noise = (s->noise + 3) & 7;
  73         switch ((value >> 4) & 7) {
  74         case 1: s->output += s->noise ^ 2; break;
  75         case 3: s->output += s->noise ^ 0; break;
  76         case 4: s->output += s->noise ^ 7; break;
  77         case 5: s->output += s->noise ^ 5; break;
  78         }
  79
  80         if (value & CB_MODE)
  81             s->output >>= 4;    /* 8 bits instead of 12 */
  82
  83         break;
  84     case 1:
  85         s->cycle = 0;
  86         break;
  87     }
  88     return s->output;
  89 }
  90
  91 static void ads7846_ts_event(void *opaque,
  92                 int x, int y, int z, int buttons_state)
  93 {
  94     ADS7846State *s = opaque;
  95
  96     if (buttons_state) {
  97         x = 0x7fff - x;
  98         s->input[1] = ADS_XPOS(x, y);
  99         s->input[3] = ADS_Z1POS(x, y);
 100         s->input[4] = ADS_Z2POS(x, y);
 101         s->input[5] = ADS_YPOS(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 int ads7856_post_load(void *opaque, int version_id)
 112 {
 113     ADS7846State *s = opaque;
 114
 115     s->pressure = 0;
 116     ads7846_int_update(s);
 117     return 0;
 118 }
 119
 120 static const VMStateDescription vmstate_ads7846 = {
 121     .name = "ads7846",
 122     .version_id = 0,
 123     .minimum_version_id = 0,
 124     .minimum_version_id_old = 0,
 125     .post_load = ads7856_post_load,
 126     .fields      = (VMStateField[]) {
 127         VMSTATE_INT32_ARRAY(input, ADS7846State, 8),
 128         VMSTATE_INT32(noise, ADS7846State),
 129         VMSTATE_INT32(cycle, ADS7846State),
 130         VMSTATE_INT32(output, ADS7846State),
 131         VMSTATE_END_OF_LIST()
 132     }
 133 };
 134
 135 static int ads7846_init(SSISlave *dev)
 136 {
 137     ADS7846State *s = FROM_SSI_SLAVE(ADS7846State, dev);
 138
 139     qdev_init_gpio_out(&dev->qdev, &s->interrupt, 1);
 140
 141     s->input[0] = ADS_TEMP0;    /* TEMP0 */
 142     s->input[2] = ADS_VBAT;     /* VBAT */
 143     s->input[6] = ADS_VAUX;     /* VAUX */
 144     s->input[7] = ADS_TEMP1;    /* TEMP1 */
 145
 146     /* We want absolute coordinates */
 147     qemu_add_mouse_event_handler(ads7846_ts_event, s, 1,
 148                     "QEMU ADS7846-driven Touchscreen");
 149
 150     ads7846_int_update(s);
 151
 152     vmstate_register(NULL, -1, &vmstate_ads7846, s);
 153     return 0;
 154 }
 155
 156 static void ads7846_class_init(ObjectClass *klass, void *data)
 157 {
 158     SSISlaveClass *k = SSI_SLAVE_CLASS(klass);
 159
 160     k->init = ads7846_init;
 161     k->transfer = ads7846_transfer;
 162 }
 163
 164 static DeviceInfo ads7846_info = {
 165     .name = "ads7846",
 166     .size = sizeof(ADS7846State),
 167     .class_init = ads7846_class_init,
 168 };
 169
 170 static void ads7846_register_devices(void)
 171 {
 172     ssi_register_slave(&ads7846_info);
 173 }
 174
 175 device_init(ads7846_register_devices)