Linux裸机开发|电容触摸屏实验

电容触摸屏实验一、多点电容触摸屏简介

触摸屏很早就有了，一开始是电阻触摸屏，电阻触摸屏只能单点触摸，需要手指按压一定的力度才有反映；和电阻屏相比电容屏的最大优点是支持多点触摸，只需要手指轻触即可，且不需要校准。

这里我不去研究电容屏的物理原理，只关注如何使用电容屏，如何得到其多点触摸坐标值即可。本实例中使用的屏幕时ATK-7016，该屏幕时由TFT LCD + 触摸屏组合起来的，低下是LCD面板，上面是触摸面板。电容触摸屏也需要一个驱动IC，驱动IC一般会提供I2C接口给主控制，主控制器通过I2C接口来读取驱动IC里面的触摸坐标数据

本例程中的驱动IC型号是FT5426，FT5426采用15*28的驱动结构，即15个感应通道，28个驱动通道，最多支持5点电容触摸。ATK-7016的电容触摸屏部分有4个IO用于连接主控制器：SCL、SDA、RST（复位引脚）和INT（中断引脚），一般通过INT引脚来通知主控制器有触摸点按下，然后在INT中断服务函数中读取触摸数据

和其他I2C器件一样，FT5426也是通过读写寄存器来完成初始化和触摸坐标数据读取的，IMX6U的I2C之前已经介绍过，这里主要就是读写FT5426的寄存器。FT5426的I2C设备地址为0x38，FT5426主要的寄存器见下表：

二、硬件介绍

本例程用到的硬件资源如下：

LED0
RGB LCD屏幕
触摸屏
串口

触摸屏是和RGB LCD屏幕坐在一起的，所以触摸屏也在RGB LCD接口上

三、程序编写

新建touchscreen文件夹，在文件夹中创建实时时钟驱动文件bsp_ft5xx6.c和bsp_ft5xx6.h

#define FT5426_ADDR				0x38	

#define FT5426_DEVICE_MODE		0x00 	
#define FT5426_IDGLIB_VERSION	0xA1 	
#define FT5426_IDG_MODE			0xA4	
#define FT5426_TD_STATUS		0x02	
#define FT5426_TOUCH1_XH		0x03	
										 
#define FT5426_XYCOORDREG_NUM	30		
#define FT5426_INIT_FINISHED	1		
#define FT5426_INIT_NOTFINISHED	0		

#define FT5426_TOUCH_EVENT_DOWN			0x00	
#define FT5426_TOUCH_EVENT_UP			0x01	
#define FT5426_TOUCH_EVENT_ON			0x02	
#define FT5426_TOUCH_EVENT_RESERVED		0x03	


struct ft5426_dev_struc
{	
	unsigned char initfalg;		
	unsigned char intflag;		
	unsigned char point_num;	
	unsigned short x[5];		
	unsigned short y[5];		

};

extern struct ft5426_dev_struc ft5426_dev;


void ft5426_init(void);

void gpio1_io9_irqhandler(void);
unsigned char ft5426_write_byte(unsigned char addr,unsigned char reg, unsigned char data);
unsigned char ft5426_read_byte(unsigned char addr,unsigned char reg);
void ft5426_read_len(unsigned char addr,unsigned char reg,unsigned char len,unsigned char *buf);
void ft5426_read_tpnum(void);
void ft5426_read_tpcoord(void);

struct ft5426_dev_struc ft5426_dev;


void ft5426_init(void)
{
	unsigned char reg_value[2];

	ft5426_dev.initfalg = FT5426_INIT_NOTFINISHED;
	int i;
	for( i = 0; i < 5; i++ )
	{	
		ft5426_dev.x[i] = 0;
		ft5426_dev.y[i] = 0;
	}
	ft5426_dev.point_num = 0;

	
	IOMUXC_SetPinMux(IOMUXC_UART5_TX_DATA_I2C2_SCL,1);
	IOMUXC_SetPinMux(IOMUXC_UART5_RX_DATA_I2C2_SDA,1);

	
	IOMUXC_SetPinConfig(IOMUXC_UART5_TX_DATA_I2C2_SCL,0x70B0);
	IOMUXC_SetPinConfig(IOMUXC_UART5_RX_DATA_I2C2_SDA,0x70B0);
	
	
	gpio_pin_config_t ctintpin_config;

	IOMUXC_SetPinMux(IOMUXC_GPIO1_IO09_GPIO1_IO09,0);		
	IOMUXC_SetPinMux(IOMUXC_SNVS_SNVS_TAMPER9_GPIO5_IO09,0);
	
	IOMUXC_SetPinConfig(IOMUXC_GPIO1_IO09_GPIO1_IO09,0xF080);
	IOMUXC_SetPinConfig(IOMUXC_SNVS_SNVS_TAMPER9_GPIO5_IO09,0x10B0);

	
	ctintpin_config.direction = kGPIO_DigitalInput;
	ctintpin_config.interruptMode = kGPIO_IntRisingOrFallingEdge;
	gpio_init(GPIO1, 9, &ctintpin_config);

	GIC_EnableIRQ(GPIO1_Combined_0_15_IRQn);				
	system_register_irqhandler(GPIO1_Combined_0_15_IRQn, (system_irq_handler_t)gpio1_io9_irqhandler, NULL);	
	gpio_enableint(GPIO1, 9);								

	
    ctintpin_config.direction=kGPIO_DigitalOutput;	
    ctintpin_config.interruptMode=kGPIO_NoIntmode;	
    ctintpin_config.outputLogic=1;					   
    gpio_init(GPIO5, 9, &ctintpin_config); 

	
	i2c_init(I2C2);	

	
	gpio_pinwrite(GPIO5, 9, 0);	
	delayms(20);
	gpio_pinwrite(GPIO5, 9, 1); 
	delayms(20);

	ft5426_write_byte(FT5426_ADDR, FT5426_DEVICE_MODE, 0); 	
	ft5426_write_byte(FT5426_ADDR, FT5426_IDG_MODE, 1); 	

	
	ft5426_read_len(FT5426_ADDR, FT5426_IDGLIB_VERSION, 2, reg_value);
	printf("Touch Frimware Version:%#Xrn", ((unsigned short)reg_value[0] << 8) + reg_value[1]);
	
	ft5426_dev.initfalg = FT5426_INIT_FINISHED;	
	ft5426_dev.intflag = 0;
}


void gpio1_io9_irqhandler(void)
{ 
	if(ft5426_dev.initfalg == FT5426_INIT_FINISHED)
	{
		//ft5426_dev.intflag = 1;
		ft5426_read_tpcoord();
	}
	gpio_clearintflags(GPIO1, 9); 
}



unsigned char ft5426_write_byte(unsigned char addr,unsigned char reg, unsigned char data)
{
    unsigned char status=0;
    unsigned char writedata=data;
    struct i2c_transfer masterXfer;
	
    
   	masterXfer.slaveAddress = addr; 			
    masterXfer.direction = kI2C_Write;			
    masterXfer.subaddress = reg;				
    masterXfer.subaddressSize = 1;				
    masterXfer.data = &writedata;				
    masterXfer.dataSize = 1;  					

    if(i2c_master_transfer(I2C2, &masterXfer))
        status=1;
        
    return status;
}


unsigned char ft5426_read_byte(unsigned char addr,unsigned char reg)
{
	unsigned char val=0;
	
	struct i2c_transfer masterXfer;	
	masterXfer.slaveAddress = addr;				
    masterXfer.direction = kI2C_Read;			
    masterXfer.subaddress = reg;				
    masterXfer.subaddressSize = 1;				
    masterXfer.data = &val;						
    masterXfer.dataSize = 1;					
	i2c_master_transfer(I2C2, &masterXfer);

	return val;
}


void ft5426_read_len(unsigned char addr,unsigned char reg,unsigned char len,unsigned char *buf)
{	
	struct i2c_transfer masterXfer;	
	
	masterXfer.slaveAddress = addr;				
    masterXfer.direction = kI2C_Read;			
    masterXfer.subaddress = reg;				
    masterXfer.subaddressSize = 1;				
    masterXfer.data = buf;						
    masterXfer.dataSize = len;					
	i2c_master_transfer(I2C2, &masterXfer);
} 


void ft5426_read_tpnum(void)
{
	ft5426_dev.point_num = ft5426_read_byte(FT5426_ADDR, FT5426_TD_STATUS);
}


void ft5426_read_tpcoord(void)
{
	unsigned char i = 0;
	unsigned char type = 0;
	//unsigned char id = 0;
	unsigned char pointbuf[FT5426_XYCOORDREG_NUM];
	
	ft5426_dev.point_num = ft5426_read_byte(FT5426_ADDR, FT5426_TD_STATUS);

	
	ft5426_read_len(FT5426_ADDR, FT5426_TOUCH1_XH, FT5426_XYCOORDREG_NUM, pointbuf);
		
	for(i = 0; i < ft5426_dev.point_num ; i++)
	{
		unsigned char *buf = &pointbuf[i * 6];
		
		ft5426_dev.x[i] = ((buf[2] << 8) | buf[3]) & 0x0fff;
		ft5426_dev.y[i] = ((buf[0] << 8) | buf[1]) & 0x0fff;
		
		type = buf[0] >> 6;	
		
		
		//id = (buf[2] >> 4) & 0x0f;
		
		if(type == FT5426_TOUCH_EVENT_DOWN || type == FT5426_TOUCH_EVENT_ON )
		{
		
		} else  {		
			
		}
	}	
}

主函数main.c中编写测试程序

 void imx6ul_hardfpu_enable(void)
{
	uint32_t cpacr;
	uint32_t fpexc;

	
	cpacr = __get_CPACR();
	cpacr = (cpacr & ~(CPACR_ASEDIS_Msk | CPACR_D32DIS_Msk))
		   |  (3UL << CPACR_cp10_Pos) | (3UL << CPACR_cp11_Pos);
	__set_CPACR(cpacr);
	fpexc = __get_FPEXC();
	fpexc |= 0x40000000UL;	
	__set_FPEXC(fpexc);
}


int main(void)
{
 	unsigned char i = 0;
	unsigned char state = OFF;

	imx6ul_hardfpu_enable();	
	int_init(); 				
	imx6u_clkinit();			
	delay_init();				
	clk_enable();				
	led_init();					
	beep_init();				
	uart_init();				
	lcd_init();							
	
	 
	if(tftlcd_dev.id == ATK7016 || tftlcd_dev.id == ATK7084) {
		ft5426_init();
	} else if(tftlcd_dev.id == ATK4384|| tftlcd_dev.id == ATK4342) {
		gt9147_init();
	}

	tftlcd_dev.forecolor = LCD_RED;
	lcd_show_string(50, 10, 400, 24, 24, (char*)"IMX6U-ALPHA TOUCH SCREEN TEST");  
	lcd_show_string(50, 40, 200, 16, 16, (char*)"TOUCH SCREEN TEST");  
	lcd_show_string(50, 60, 200, 16, 16, (char*)"ATOM@ALIENTEK");  
	lcd_show_string(50, 80, 200, 16, 16, (char*)"2019/3/27");  
	
	lcd_show_string(50, 110, 400, 16, 16,	(char*)"TP Num	:");  
	lcd_show_string(50, 130, 200, 16, 16,	(char*)"Point0 X:");  
	lcd_show_string(50, 150, 200, 16, 16,	(char*)"Point0 Y:");  
	lcd_show_string(50, 170, 200, 16, 16,	(char*)"Point1 X:");  
	lcd_show_string(50, 190, 200, 16, 16,	(char*)"Point1 Y:");  
	lcd_show_string(50, 210, 200, 16, 16,	(char*)"Point2 X:");  
	lcd_show_string(50, 230, 200, 16, 16,	(char*)"Point2 Y:");  
	lcd_show_string(50, 250, 200, 16, 16,	(char*)"Point3 X:");  
	lcd_show_string(50, 270, 200, 16, 16,	(char*)"Point3 Y:");  
	lcd_show_string(50, 290, 200, 16, 16,	(char*)"Point4 X:");  
	lcd_show_string(50, 310, 200, 16, 16,	(char*)"Point4 Y:");  
	tftlcd_dev.forecolor = LCD_BLUE;
	
	while(1)					
	{
		if(tftlcd_dev.id == ATK7016 || tftlcd_dev.id == ATK7084) {
			lcd_shownum(50 + 72, 110, ft5426_dev.point_num , 1, 16);
			lcd_shownum(50 + 72, 130, ft5426_dev.x[0], 5, 16);
			lcd_shownum(50 + 72, 150, ft5426_dev.y[0], 5, 16);
			lcd_shownum(50 + 72, 170, ft5426_dev.x[1], 5, 16);
			lcd_shownum(50 + 72, 190, ft5426_dev.y[1], 5, 16);
			lcd_shownum(50 + 72, 210, ft5426_dev.x[2], 5, 16);
			lcd_shownum(50 + 72, 230, ft5426_dev.y[2], 5, 16);
			lcd_shownum(50 + 72, 250, ft5426_dev.x[3], 5, 16);
			lcd_shownum(50 + 72, 270, ft5426_dev.y[3], 5, 16);
			lcd_shownum(50 + 72, 290, ft5426_dev.x[4], 5, 16);
			lcd_shownum(50 + 72, 310, ft5426_dev.y[4], 5, 16);
		} else if(tftlcd_dev.id == ATK4384|| tftlcd_dev.id == ATK4342) {
			lcd_shownum(50 + 72, 110, gt9147_dev.point_num , 1, 16);
			lcd_shownum(50 + 72, 130, gt9147_dev.x[0], 5, 16);
			lcd_shownum(50 + 72, 150, gt9147_dev.y[0], 5, 16);
			lcd_shownum(50 + 72, 170, gt9147_dev.x[1], 5, 16);
			lcd_shownum(50 + 72, 190, gt9147_dev.y[1], 5, 16);
			lcd_shownum(50 + 72, 210, gt9147_dev.x[2], 5, 16);
			lcd_shownum(50 + 72, 230, gt9147_dev.y[2], 5, 16);
			lcd_shownum(50 + 72, 250, gt9147_dev.x[3], 5, 16);
			lcd_shownum(50 + 72, 270, gt9147_dev.y[3], 5, 16);
			lcd_shownum(50 + 72, 290, gt9147_dev.x[4], 5, 16);
			lcd_shownum(50 + 72, 310, gt9147_dev.y[4], 5, 16);
		}
		delayms(10);
		i++;
	
		if(i == 50)
		{	
			i = 0;
			state = !state;
			led_switch(LED0,state); 
		}
	}
	return 0;
}

四、下载验证

修改Makefile文件：修改TARGET为touchscreen，追加“bsp/touchscreen”文件夹
使用imxdownload软件将bin文件下载到SD卡中
烧写成功后，插入SD卡，复位开发板后，用手指触摸屏幕时就会在LCD上显示出当前的触摸点个数及对应的触摸值

Linux裸机开发|电容触摸屏实验

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