Remember that I said we probably didn't need the WAKEUP signal. I'm so glad you ignored me. Today I managed to put the DW into a deep sleep, from which it was supposed to wake up after 5 seconds. It didn't.
Worse still I couldn't get it to wake up by resetting it.
The manual says that another way to wake it up is to hold the Chip Sel low for 200uS and read a whole bunch of data. That didn't work
So I was left with the WAKEUP line, which has to be held high for 200 uS. Fortunately this worked.
I thought I had a door stop for a while!