I2C Transfers between Arduinos - Handshaking

[srnet]

I did some searching on 'clock stretching' and found this discussion on the topic, which is the same as my problem really;

delay I2C slave response - clock stretching

Hi all. I'm writing the code for a I2C slave Arduino (Nano Every, if it matters). I'm using the Wire library. I need to perform some slow operations before replying to the I2C master, and I need to use the clock stretch feature in order to keep the master waiting. It seems to me the that when my onRequest() callback get called my code must reply, no matter what, but the response payload isn't ready yet. Is there a way to set the clock stretch and delay the response to a later time? If Wire c…

So sounds like its not possible.