One way is to use a humble pi breakout board, discard the supplied 26pin female header and instead solder a 26pin female extender header, plug in the humble pi to the PI first then the piface on top, on the humble pi board you can bring out any pin from the PI gpio port and add you sensor connections etc
hum... yeah, i was thinking in something like idle cable, master/ slave configuration... I know piface dont use all the pins, but i dont know the piface schematics for the board... any help?
thanks a lot
PiFace Digital is connected to RPi via SPI so it uses only a few pins (MOSI, MISO, SCLK, GND, 3.3V, 5V). Using e.g. GPIO#4 for 1-Wire is possible, you just need to solder the wires to the unused pins on PiFace.