i²c bus

Hello
My friends and I are searching for a solution for our problem.
We want to control relays on multiple places with a type of bus system. But we need to have a feedback from the slaves so we can read the input pins of the slaves and control it at the same time with the master. So the master knows witch slave input pins are high.

thanks.
sorry for my bad English
Greets from Belgium! 8)

But we need to have a feedback from the slaves so we can read the input pins of the slaves and control it at the same time with the master. So the master knows witch slave input pins are high.

By "input pins of the slaves" do you mean the pins that turn on the relays or something else ? If the former then surely you will know their state because you set it from the master.

we control the relays with output pins on the slave controlled by the master.
but we want to use a input pin on the slave to check the state of the relay for safety purposes. So we are sure when the relay is open or closed. :smiley:

You can use I2C GPIO port expanders, such as the MCP23017. They are bi directional.