i2c with pcf8591 - Raspberry Pi Forums

hello there,
interfacing i2c pcf8591 , want read it.
have example code in

code: select all

void i2c_init()                            { fd=open("/dev/i2c/0",o_rdwr);                  // file open i2c communication in read-write mode if (fd<0) { printf("\n not able open driver \n"); } else { printf("\n i2c working \n"); } }  //*****************************************************************************************************// //***********************i2c read using external adc*********************************************// //*****************************************************************************************************//  int i2c_read(adc_channell) { if (adc_channell==0)                           // chanel 0 used data acqustion { buf[0]=0x90;                                   // sending control word adc write mode in ch=0 } buf[1]=0x40;                                   // i2c adress arm on adc connected                                  buf[2]=0x91;                                   // control word adc set in read mode io=ioctl(fd,0x703,0x48);                       // address arm i2c communication if(io<0) { printf("error ioctl\n"); } else { wbyte=write(fd,buf,3);                        // write 3 control word arm  usleep(1*1000); if(wbyte!=3) { printf("error write:%d\n",wbyte); } rbyte=read(fd,buff,10);                      // read 10 bytes adc  usleep(10*1000); for(i=0;i<=5;i++) {                                            // average , conversion in voltage valuee=(buff[i]*5)/255;  m1=m1+valuee; printf("\n%x",buff[i]); printf("\n voltage = %fv",value); } m1=m1/5; printf("%fv",m1); } return(m1); } 

can tell me ioctl(fd,0x703,0x48) these address.
don't understand it.

ioctl number 0x703 used set i2c slave address.

tells i2c device talk in next command(s). asking talk device 0x48 (decimal 72).

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