You're right, but the question is: How does it work with Arduino's Wire library? That's what I don't know. The example that I have shows the sequence as: Slave Address, Command, Slave Address, Data (see http://www2.neufeld.newton.ks.us/images/electronics/2008/05/26/PCA9535-figure-8.png). And that's what the receive code that I have found does. But I don't want to do that, p.8 of the data sheet says that reading the MPR084 proceeds like this, in a nutshell: Slave Address, Command, Data.
...In your example at www.gammon.com.au, say under "Request Response" about 3/4 through the page, I see that you do your sendCommand() this way:
Wire.beginTransmission (SLAVE_ADDRESS);
Wire.send (cmd);
Wire.endTransmission ();
Wire.requestFrom (SLAVE_ADDRESS, responseSize);
...my interpretation is that the beginTransmission / send / endTransmission will actually send the Slave Address and the Command onto the wire. Now the MPR084 will send data. But the requestFrom requires the Slave Address, which would also fit into the scheme shown at http://www2.neufeld.newton.ks.us/images/electronics/2008/05/26/PCA9535-figure-8.png - It appears to me that the Slave Address will then be sent out onto the wire. But I don't want to send it again, because the MPR084 should be sending at this point, so what would I do? How to just receive the data at this point, without addressing further?
Well I have been out all day today and I have to go to bed so I will send the schematic and my code asap. Thanks for your attention.