A Slave like UNO-2 of Post#8 can initiate data transfer by turning itself into a Master.
That makes it a multi master system, it does not have to do that and I have had enough trouble with multi master systems professionally to put me off using one especially where there is no need to.
cattledog:
To gain a clue to the timing, perhaps you can turn on a led in the .onRequest() handler and see when it happens in relationship to the slider movement.
The problem is that I don't have the hardware at the moment. It is a joint project and I have passed it on to the person writing the master code.
Can you please post the movement function which appears to not get interrupted?
OK I will post the whole of the code. Hardware notes, a port expander controls the motors and a AT85 has the job of updating and driving the LEDs.
Too big to post so I will use an attachment.
Four_Sliders_I2C.zip (4.27 KB)