Finally I have an Arduino Leornado to control it all.
The end plan is to read an RFID tag, and then send it’s value out to a computer on a network.
If I plug just the Ethernet shield in, I can write a sketch that sends a message out over the network using the standard Ethernet library.
If I plug just the RFID shield in, I can read, write tags.
As soon as I plug both shields in, neither then work as expected. As far as I can tell, the soldering on all the pins is good, and all the pins line up.
My crappy work around at the moment is to have two Arduino’s, one with each shield and then use the i2c on pins a4 and a5 to send the rfid data over to the other Arduino.
There must be a simple reason that the shields aren’t both working together. My current guess is that they’re both using the sck, Mosi, and Misi pins, but that’s just a guess.
What’s the next step in my trouble shooting, or can anyone give me some advice?
Stacking shields raise the question if the top shield receives the needed signals, unaffected.
There might be conflicts, both shields wants to use the same pin.
One way to find could be to inspect the libraries involved, what pins do they use.
I think both shields are using the SPI on pins 11, 12,13.
So I need to learn about how to use the chip select, to only enable the Ethernet shield, once we have received RFID data. Will there then be a delay waiting for the Ethernet shield to reconnect to the network?
IF any of the gear thereon is SPI, that is exactly how it should be, and there should be no need to check any libraries. Since you have had the shields working separately you already know which pins you need to use and about the only pins that can cause grief is a clash of device select pins, which should be already painfully obvious. This to the point where I suspect your problem lies somewhere else entirely. It might be simply a matter of inadequate power, particularly as Ethernet shields aren't famous for their frugality. In the unlikely event that there is a clash with the SS pins, that should be fixable. The RFID shield may well have jumper select for the SS pin.