Communication between 2 arduinos using I2C/SPI and Matlab Simulik

Hi,

I am trying to communicate between two arduino boards (a Feather and a Due). I am using Simulink for programming my boards, but from my understanding, the I2C/SPI blocks in the Arduniolib in simulink are designed for the arduino to be the master. Is there any code/trick out there so I can define an arduino as a slave board in Simulink? I am assuming if no such block exists, I should write my own S function block. Is anybody aware of such block. Please share if you have any solutions or experience you have about this.

Thanks in advance, Mohsen