首先来分析一下触摸屏的原理：
首先，它属于输入子系统。还记得我们上篇分析的关于linux输入子系统的架构吗？？？
这里找来了另一张图片：小弟先敬上：
好了，先来一段废话 触摸屏原理分析：（已知的朋友可绕道）
原理：由横向电阻比和纵向电阻比组成。由nYPON、YMON、nXPON、XMON四个控制信号控制4个MOS管（S1-S4）的通断。（实质也是同鼠标一样获取坐标）
S3C2440触摸屏控制器2种模式：
X/Y位置分别转换模式
X/Y位置自动转换模式
工作流程：
选择模式
设置触摸屏接口到等待接口状态
如果中断发生，激活转换模式
获取坐标后，返回等待中断状态
（INT_TC中断用于按下或弹起触摸屏）
（INT_ADC用于坐标转换完成）
下面以tq2440触摸屏为例：
/*************************************
NAME:tq2440_ts.c
COPYRIGHT:www.embedsky.net
*************************************/
#include <linux/errno.h>
#include <linux/kernel.h>
#include <linux/module.h>
#include <linux/slab.h>
#include <linux/input.h>
#include <linux/init.h>
#include <linux/serio.h>
#include <linux/delay.h>
#include <linux/platform_device.h>
#include <linux/clk.h>
#include <asm/io.h>
#include <asm/irq.h>
#include <plat/regs-adc.h>
#include <mach/regs-gpio.h>
/* For ts.dev.id.version */
#define S3C2410TSVERSION 0x0101
#define WAIT4INT(x) (((x)<<8) | \
S3C2410_ADCTSC_YM_SEN | S3C2410_ADCTSC_YP_SEN | S3C2410_ADCTSC_XP_SEN | \
S3C2410_ADCTSC_XY_PST(3))
#define AUTOPST (S3C2410_ADCTSC_YM_SEN | S3C2410_ADCTSC_YP_SEN | S3C2410_ADCTSC_XP_SEN | \
S3C2410_ADCTSC_AUTO_PST | S3C2410_ADCTSC_XY_PST(0))
static char *tq2440ts_name = "TQ2440 TouchScreen";
static struct input_dev *dev;
static long xp;
static long yp;
static int count;
extern struct semaphore ADC_LOCK;
static int OwnADC = 0;
static void __iomem *base_addr;
/*
static inline void tq2440_ts_connect(void)
{
s3c2410_gpio_cfgpin(S3C2410_GPG12, S3C2410_GPG12_XMON);
s3c2410_gpio_cfgpin(S3C2410_GPG13, S3C2410_GPG13_nXPON);
s3c2410_gpio_cfgpin(S3C2410_GPG14, S3C2410_GPG14_YMON);
s3c2410_gpio_cfgpin(S3C2410_GPG15, S3C2410_GPG15_nYPON);
}
*/
static void touch_timer_fire(unsigned long data)
{
unsigned long data0;
unsigned long data1;
int updown;
data0 = ioread32(base_addr+S3C2410_ADCDAT0);
data1 = ioread32(base_addr+S3C2410_ADCDAT1);
updown = (!(data0 & S3C2410_ADCDAT0_UPDOWN)) && (!(data1 & S3C2410_ADCDAT0_UPDOWN));
if (updown) {
if (count != 0)
{
long tmp;
tmp = xp;
xp = yp;
yp = tmp;
xp >>= 2;
yp >>= 2;
input_report_abs(dev, ABS_X, xp);
input_report_abs(dev, ABS_Y, yp);
input_report_key(dev, BTN_TOUCH, 1);
input_report_abs(dev, ABS_PRESSURE, 1);
input_sync(dev);
}
xp = 0;
yp = 0;
count = 0;
iowrite32(S3C2410_ADCTSC_PULL_UP_DISABLE | AUTOPST, base_addr+S3C2410_ADCTSC);
iowrite32(ioread32(base_addr+S3C2410_ADCCON) | S3C2410_ADCCON_ENABLE_START, base_addr+S3C2410_ADCCON);
}
else
{
count = 0;
input_report_key(dev, BTN_TOUCH, 0);
input_report_abs(dev, ABS_PRESSURE, 0);
input_sync(dev);
iowrite32(WAIT4INT(0), base_addr+S3C2410_ADCTSC);
if (OwnADC)
{
OwnADC = 0;
up(&ADC_LOCK);
}
}
}
static struct timer_list touch_timer =
TIMER_INITIALIZER(touch_timer_fire, 0, 0);
static irqreturn_t stylus_updown(int irq, void *dev_id)
{
unsigned long data0;
unsigned long data1;
int updown;
if (down_trylock(&ADC_LOCK) == 0)
{
OwnADC = 1;
data0 = ioread32(base_addr+S3C2410_ADCDAT0);
data1 = ioread32(base_addr+S3C2410_ADCDAT1);
updown = (!(data0 & S3C2410_ADCDAT0_UPDOWN)) && (!(data1 & S3C2410_ADCDAT0_UPDOWN));
if (updown)
{
touch_timer_fire(0);
}
else
{
OwnADC = 0;
up(&ADC_LOCK);
}
}
return IRQ_HANDLED;
}
static irqreturn_t stylus_action(int irq, void *dev_id)
{
unsigned long data0;
unsigned long data1;
if (OwnADC)
{
data0 = ioread32(base_addr+S3C2410_ADCDAT0);
data1 = ioread32(base_addr+S3C2410_ADCDAT1);
xp += data0 & S3C2410_ADCDAT0_XPDATA_MASK;
yp += data1 & S3C2410_ADCDAT1_YPDATA_MASK;
count++;
if (count < (1<<2))
{
iowrite32(S3C2410_ADCTSC_PULL_UP_DISABLE | AUTOPST, base_addr+S3C2410_ADCTSC);
iowrite32(ioread32(base_addr+S3C2410_ADCCON) | S3C2410_ADCCON_ENABLE_START, base_addr+S3C2410_ADCCON);
}
else
{
mod_timer(&touch_timer, jiffies+1);
iowrite32(WAIT4INT(1), base_addr+S3C2410_ADCTSC);
}
}
return IRQ_HANDLED;
}
static struct clk *adc_clock;
static int __init tq2440ts_init(void)
{
struct input_dev *input_dev;
adc_clock = clk_get(NULL, "adc");
if (!adc_clock)
{
printk(KERN_ERR "failed to get adc clock source\n");
return -ENOENT;
}
clk_enable(adc_clock);
base_addr=ioremap(S3C2410_PA_ADC,0x20);
if (base_addr == NULL)
{
printk(KERN_ERR "Failed to remap register block\n");
return -ENOMEM;
}
/* Configure GPIOs */
// tq2440_ts_connect();
iowrite32(S3C2410_ADCCON_PRSCEN | S3C2410_ADCCON_PRSCVL(0xFF),base_addr+S3C2410_ADCCON);
iowrite32(0xffff, base_addr+S3C2410_ADCDLY);
iowrite32(WAIT4INT(0), base_addr+S3C2410_ADCTSC);
/* Initialise input stuff */
input_dev = input_allocate_device();
if (!input_dev)
{
printk(KERN_ERR "Unable to allocate the input device !!\n");
return -ENOMEM;
}
dev = input_dev;
dev->evbit[0] = BIT(EV_SYN) | BIT(EV_KEY) | BIT(EV_ABS);
dev->keybit[BITS_TO_LONGS(BTN_TOUCH)] = BIT(BTN_TOUCH);
input_set_abs_params(dev, ABS_X, 0, 0x3FF, 0, 0);
input_set_abs_params(dev, ABS_Y, 0, 0x3FF, 0, 0);
input_set_abs_params(dev, ABS_PRESSURE, 0, 1, 0, 0);
dev->name = tq2440ts_name;
dev->id.bustype = BUS_RS232;
dev->id.vendor = 0xDEAD;
dev->id.product = 0xBEEF;
dev->id.version = S3C2410TSVERSION;
if (request_irq(IRQ_ADC, stylus_action, IRQF_SHARED|IRQF_SAMPLE_RANDOM, tq2440ts_name, dev))
{
printk(KERN_ERR "tq2440_ts.c: Could not allocate ts IRQ_ADC !\n");
iounmap(base_addr);
return -EIO;
}
if (request_irq(IRQ_TC, stylus_updown, IRQF_SAMPLE_RANDOM, tq2440ts_name, dev))
{
printk(KERN_ERR "tq2440_ts.c: Could not allocate ts IRQ_ADC !\n");
iounmap(base_addr);
return -EIO;
}
printk(KERN_INFO "%s successfully loaded\n", tq2440ts_name);
input_register_device(dev);
return 0;
}
static void __exit tq2440ts_exit(void)
{
disable_irq(IRQ_ADC);
disable_irq(IRQ_TC);
free_irq(IRQ_TC,dev);
free_irq(IRQ_ADC,dev);
if (adc_clock)
{
clk_disable(adc_clock);
clk_put(adc_clock);
adc_clock = NULL;
}
input_unregister_device(dev);
iounmap(base_addr);
}
module_init(tq2440ts_init);
module_exit(tq2440ts_exit);
关于代码的分析，大家可以参考：http://www.360doc.com/content/11/1111/16/1317564_163585743.shtml 关于字符驱动与输入子系统的知识，我们暂时结束了。。。。。。。。。。。。
嗨！！！朋友，，，，喝杯奶茶去
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