PiFace CAD: What are the really used PINs on the PI

Look at What GPIO pins are used by the Piface CAD shield? as well as PiFace Control and Display | Raspberry Alpha Omega

Hi Clem,

thank you for the answer. I took a look and except what was on the E14 site the other I already know. The problem is that I don't find a connecto schemarics of the specific PiFaceCAD. As a matter of fact it is not difficult to replicate the GPIO connector but it seems that the only documentation available is for the setting of other stackable PiFace boards, all using the same I2C bus so things are simple. What I am trying to understand is if these devices ONLY use the I2C + power and gnd or there are other GPIO pin used for some reason.

Enrico

By implication the GPIO pins seem all used based on comment at the end of the second link. But I do not know for sure.

Exactly what I thoug, but in the meantime, how is it possible to stack up to five different addressable boards (or multiple identical) on the PiFace rack only changing the I2C addressing bits? This seems confictual.

Enrico

No problem since all boards listen and react only if they see their own address on the line

So you mena that the I2C addressing is not barely to manage a chip but the entire board that "works" only when the righe bus commands are sent ?

The data address is required to pick which chip will respond to the stream that follows. It is data/software driven and not electrical. This works as long as each electrical board has a unique address set.

Clem

You are really very helpful Clem ! Your suggestions are raising an idea. Please can you tell me me if I am not wrong:

the entire board expect - to work instead ignoring signals - to be "activated" in some way through a I2C addressing. This - if so - seems reasonable. But what kind of chip can be used to address the entire board?

Thank you. Enrico

P.S. I was aware that it was a problem of logic signals instead of electric as all the stackable boards are always connected and powered

Rather than trying to redo some good tutorials, here is a couple that woirked for me: http://www.best-microcontroller-projects.com/i2c-tutorial.html and http://tronixstuff.com/2010/10/20/tutorial-arduino-and-the-i2c-bus/

Of course let me know where the details are muddy and I will get water to sprain off that area (give help of course).

Clem

Got the links Clem.

I think I have explained in a bad form. I know almost well what the I2C bus is and I have used it a in past. When I mare from scratch the Mill Machine controller based on the Arduino Duemilanove I added several pieces with too less PINs As a matter of fact the g-code engine, preset, settings (e.g. zero point and limits, measure units, working space coords etc.) was done by Arduino. Only a high level 3D commands was sent via Maxx232 serial from the PC on a Processing rendering engine. So, I have used I2C EEPROMs to manage a sql-like database, two shift-out registers, a shift-in register and other IC based on I2C (including a real-time clock).

All these things was single IC that the micro controller board was properly addressing on the single bus. What instead I am searching for - if exists, but I suppose yes - and that I don't know what it is if it is possible to condition the entire board with a sort of X-I2C IC. When I address this chip, that as a matter of fact do nothing more than - for example - setting a bit or something like this, my board react and as the address is different than the one of the PiFaceCAD (or in general any other PIFace board) these boards do nothing. As least this is the idea.

Enrico