Set the bus speed to 100kHz. That was the original definition by Philips Semiconductor for the I2C-Bus.
This value is also given in the datasheet of the PCF8570.
As I have already written, my "Bus Pirate" is on the way from China to Switzerland.
As soon as it arrives, I can send you the commands.
Have you been able to read through the document in the meantime?
I think after you've written a script, we should include it in the document as an example.