Display-o-Tron is working perfectly on a Pi3+.
Piface 2 Digital io relay board is working perfectly on a Pi3+
When they are both connected the Display-o-Tron display is not updated, only the cursor flashes.
They keypad responds perfectly.
I have tried changing the hardware addressing on the PiFace but this has had no effect.
Someone much cleverer than I suggested it might be possible to change SPI I2C control addresses but I have no idea how to do that.
Any suggestions welcome.