Limited GPIO Pins

Please ignore my last message. 

I completely forgot that the Raspberry Pi has 8 GND pins and not 5. 

I apologise for my carelessness. 

Posted by: @sumanta

P.S. What's the need of those pins labelled as NC in the datasheet?

@davee After a bit of research, I found that these NC pins(Not Connected) aren't actually connected to anything, although they are physically connected to GPIO pins. 

I was wondering, that in this way, 12 pins on the Pi, would be wasted for nothing.(When we connect Pi and display directly).

But by framing out our plan, we've saved 16 GPIO pins (2 5V, 2 3.3V, 12 NC pins) 😀 😀 

Hi @sumanta,

  Yes, looking at the connector on your first photo, I assumed that only those pins shown would be connected ... the other pins were NC on the display board. But of course the R Pi pins covered by the display connector will be difficult to connect to for your sensors, etc.

Hence I suggested choices of soldering a connector on the back of the R Pi board (which understandably you declined) or using flexible wires, instead of pushing the R Pi and display boards back to back.

As for ground pins (and also power 5V or 3.3V), it is 'often permissable' to use 1 pin to go to two or more places, so you don't need to count them in the 'strict' sense required for I/O pins. The thing to avoid when sharing a ground pin, is using the same pin for a high current circuit (e.g. a power return) and a low level circuit, such as is often the case for a sensor.

Posted by: @davee

The thing to avoid when sharing a ground pin, is using the same pin for a high current circuit (e.g. a power return) and a low level circuit, such as is often the case for a sensor.

@davee Thanks for this advice. 😀

I have decided to allocate 5 GND pins on the Pi to connect to the 5 GND pins on the display. 

The rest 3 GND pins on the Pi will remain free for using, while physical computing. (Although 1 GND pin is what I need) 

Okay then. I'm sticking to this plan and I'll surely inform about any developments. 😀