How rpi3 as slave use i2c with wiringPi

Question

I tried to let my rpi3 with wiringPi as slave to receive data from master and data +1 send to master .

mater send 1 to slave (rpi3)

My rpi3 SDA is GPIO 18 ,SLC is GPIO 19

the code on my rpi3 :

#include<wiringPiI2C.h>
#include<stdio.h>

int main(){
int fd;
fd = wiringPiI2CSetup(0x35); //0x35 is my slave address  
int cont=0;

while(1){
cont = wiringPiI2CReadReg8(fd,0x55); //0x55 is my regaddress
printf("readValue:%d\n",cont);//receive data from my master 
delay(1000);
wiringPiI2CWriteReg8(fd,0x55,cont++);//send data to master 
delay(1000);

}
return 0;
}

However it only show -1 , mean error

I tried to change SDA,SCL pin to GPIO 3 (SDA),5 (SCL) it would show 0 ,but it couldn't receive data

Any help on what Im doing wrong will be appreciated.

Answer 1

wiringPi does not support I2C slave mode. It only supports using the Raspberry Pi as an I2C bus master.

This in part is because wiringPi uses the underlying Linux I2C driver which only supports master mode.