Greetings and Happy Holidays:
My question is: is it possible to stack shield boards ? Say an UNO R3 --> Bluetooth shield --> SD card shield.
Is it possible and if so is there a limit? (I am sure of the limit on how many to stack. You would end up having a proverbial
leaning tower.
triad
It depends on what pins the shield uses. If the network card uses pins D10 to D13, you cannot use these pins for another shield when they are stacked.
Weedpharma
You can run out of sensible things to do, the ability to supply adequate power, or money before there is a structural problem. I have seen an arduino that was about fifty stories high. I have no idea of what it did - impress the natives, I suppose.
There is more than one way for pins to be shared and many, indeed usually most, pins on shields are pass through and unused thereon. That is how the system works. A specific example is the SPI bus, which uses pins 10>13, and what Weed is saying about pins 10>13 specifically, is nonsense.
The pic below is a four storey arduino. It is actually shown on a Mega, but they started out on a Uno. Next up is a commercial ethernet shield which uses SPI, pins 10>13, and has an SD card on board. The next, barely visible, is a sensor shield and has a clock which, on a Uno, is connected to the I2C bus on pins A4,5, which pass though the ethernet shield but are unused by it. Here on the Mega, the clock is connected to pins 20,21 by a flying lead. The top shield is just the display, which is also on the SPI bus, pins 11>13. The SPI pins are just pass-through on the sensor shield but shared with ethernet, and the LCD has its exclusive select pin 7.
The bluetooth is just a breakout board with a flying lead to the sensor shield. A bluetooth shield could join the rest, and just use pins 0,1, which are unused by any of the others.
Note that there are differences between Mega and Uno in the allocation of pins for the SPI bus. This is not a problem, and the most common shield using it, the ethernet cum SD shield, fits both.
The best way to find out if shield X, Y, and Z will stack is to provide their links and we can find out for you. Power consumption, pin conflict etc. as mentioned already.
Thanks Guy's. Great information. Know I will play the game of pin Soduko. I have worked with the BT LE (HO-6/5 not sure. ) and
the data it snags will download when I access it but I would just like to put the data on the SD. I will check out the jpg Nick thank
you.
On to the next problem.
triad
Tiberious Data Mining
Nick, thank you for enlightening me to the use of pins 10 to 13. I was unaware of it being SPI so have learnt something.
The mention of the pins was meant as an example of the need to be aware of what the other pins where used for rather than a specific usage.
Weedpharma
Just a bad choice then, eh?
