5718使用I2C读取感光模块的数据

5718车载显示控制器外接一个i2c环境光传感器，用来采集外部环境的光亮，从而自动调节控制器的LCD背光

环境光传感器 MAX44009

MAX44009环境光传感器提供I²C数字输出
数据手册: https://www.maximintegrated.com/cn/products/interface/sensor-interface/MAX44009.html
MAX44009.pdf

i2c-tools源码下载

源码下载链接:

https://mirrors.edge.kernel.org/pub/software/utils/i2c-tools/		使用的是3.0.2的版本

https://www.kernel.org/pub/software/utils/i2c-tools/

i2c-tools工具编译

修改对应Makefile
		PREFIX	= /home/siasun/OK5718-SDK-V1.0/OK57xx-linux-fs/usr
		CC	= arm-linux-gnueabihf-gcc
		AR	= arm-linux-gnueabihf-ar
		STRIP	= arm-linux-gnueabihf-strip

i2ctransfer工具

源码:
git clone https://git.kernel.org/pub/scm/utils/i2c-tools/i2c-tools.git

----没弄懂i2ctransfer工具数据怎么写的
疑问: 寄存器地址是怎么确定的、寄存器数据连续读多少个字节又是怎么确定的

感光自动调节背光程序

i2c_backlight.c

#include 
#include 
#include 
#include 
#include 
#include 

//double类型打印0表示位数,默认6位
//printf(" %.0lf \n",Lux);

/* 背光调节显示
	Lux范围								亮度档位
	0 - 1300 							echo  2  >  /sys/class/backlight/backlight/brightness
	1301 - 8500							echo  4  >  /sys/class/backlight/backlight/brightness
	8501 - 4177920						echo  7  >  /sys/class/backlight/backlight/brightness
	其他值								echo  3  >  /sys/class/backlight/backlight/brightness
*/

int main(){
	
	int i = 0, j = 0;
	int data[5] = { 0, 0, 0, 0, 0};
	char buff_03[10];
	char buff_04[5];
	char buff_mid[2];
	FILE * fp;
	
	while(1){
	//加判断是否有I2C设备，如果没有，则停止程序
		fp = popen("i2cget -f -y 0 0x4a 0x03", "r");
		if (!fp) 
		{
			pclose(fp);
			break;
			return -1;
		}
		
		fgets(buff_03,sizeof(buff_03),fp);
		//printf("%s\n",buff_03);
		pclose(fp);
		
		fp = popen("i2cget -f -y 0 0x4a 0x04", "r");
		if (!fp) 
		{
			pclose(fp);
			break;
			return -1;
		}
		
		fgets(buff_04,sizeof(buff_04),fp);
		//printf("%s\n",buff_04);
		pclose(fp);

		buff_03[4] = buff_04[3];
		//printf("===== %s =====\n",buff_03);
		//printf("===== %s  =====\n\n",buff_04);
		
		fprintf(stderr, "===== %s =====\n",buff_03);
		fprintf(stderr, "===== %s  =====\n\n",buff_04);
		//0x03、0x04地址数据处理---fgets读取上来是一个字符串
		for(i=2;i<=4;i++)
		{
			if(buff_03[i] >= '0' && buff_03[i] <= '9'){
				buff_mid[0] = buff_03[i];
				data[i] = atoi (buff_mid);
				//printf("\n data[%d] = %d \n",i,data[i]);
			}else if( (buff_03[i] == 'a' ) || (buff_03[i] == 'A') ){
				data[i] = 10;	
				//printf("\n data[%d] = %d \n",i,data[i]);
			}else if( (buff_03[i] == 'b' ) || (buff_03[i] == 'B') ){
				data[i] = 11;	
				//printf("\n data[%d] = %d \n",i,data[i]);
			}else if( (buff_03[i] == 'c' ) || (buff_03[i] == 'C') ){
				data[i] = 12;	
				//printf("\n data[%d] = %d \n",i,data[i]);
			}else if( (buff_03[i] == 'd' ) || (buff_03[i] == 'D') ){
				data[i] = 13;	
				//printf("\n data[%d] = %d \n",i,data[i]);
			}else if( (buff_03[i] == 'e' ) || (buff_03[i] == 'E') ){
				data[i] = 14;	
				//printf("\n data[%d] = %d \n",i,data[i]);
			}else if( (buff_03[i] == 'f' ) || (buff_03[i] == 'F') ){
				data[i] = 15;	
				//printf("\n data[%d] = %d \n",i,data[i]);
			}else{
				data[i] = 5;	
				//printf("\n data[%d] = %d \n",i,data[i]);
			}
		}

		int mantissa = 0;
		int Lux = 1;
		mantissa = data[3] * 16 + data[4];
		//printf("mantissa = %d \n",mantissa);
		if(data[2] == 0){
			Lux = mantissa;
			//printf("Lux = %d \n",Lux);
		}else{
			for(j=1;j<=data[2];j++){
				Lux = 2 * Lux;
			}
			Lux = Lux * mantissa;
			//printf("Lux = %d \n",Lux);
		}
		
		if(Lux >= 0 && Lux <= 200){
			system("echo  2  >  /sys/class/backlight/backlight/brightness");
			printf("backlight-brightness = 2 \n");
		}else if(Lux >= 201 && Lux <= 700){
			system("echo  4  >  /sys/class/backlight/backlight/brightness");
			printf("backlight-brightness = 4 \n");
		}else if(Lux >= 701 && Lux <= 11200){
			system("echo  7  >  /sys/class/backlight/backlight/brightness");
			printf("backlight-brightness = 7 \n");
		}else{
			system("echo  3  >  /sys/class/backlight/backlight/brightness");
			printf("backlight-brightness = 3 \n");
		}

		sleep(1);
	}

	return 0;
}

背光突变考虑：

采三次取平均值 {加权平均值}
PID调节
线性调节

i2c_tools工具使用参考链接:

http://wiki.100ask.org/index.php?title=I2C_i2c-tools&action=edit

https://www.cnblogs.com/raina/p/12068485.html