arduino + wifi + rfid

Hi all,

Will there any problems to combine 2 shields on the same arduino board? one for getting wifi connection and another one to be able to read rfid tags?


There are several factors to consider when combining shields.

Physical fit. You'll need to be able to stack the shields so at least one of them will need stacking headers, and high components should not foul boards stacked on top. Ethernet shields are notorious for this because the RJ45 jack is so physically high. Sometimes it can be handy to keep some spare stacking headers around to use as spacers between shields.

Pin contention. Check the pin assignments of the shields you want to use, and make sure they're not going to fight over the same pin. If your shields use SPI communications to the Arduino they can all co-exist on the SPI bus, with the exception of the CS line which will need to be configured differently for each board.

Software interaction. Shields that come with a decent amount of software overhead (such as large driver libraries) can sometimes be a pain to combine if they use up lots of Flash, or SRAM, or have conflicting interrupts or tight timing requirements. This is something that may be difficult for you to determine at face value unless you know the internals of all the libraries involved quite intimately.

With all those provisos, the short answer to your question is "it's probably OK".

Good luck!

Jon Freetronics:

After replying to this question I realised that it's probably an issue worthy of a more in-depth answer, so I wrote up some guidelines on determining shield compatibility here: