I have read that it is possible to connect multiple SPI devices to a single Arduino with them sharing the MISO, MOSI, and SCK connection and each having their own SS. Im trying to build something that will require the arduino to be able to communicate with two SPI devices simultaneously. Is that possible or does the does it have to switch communication between devices to read one at a time?
It is possible.
Pin 10 has to be set as an OUTPUT and is your first SS
Use a different pin for the second SS
You can read only one device at a time. Select SS for that device, do the operation, then deselect SS.
You can use a 74LS138, a 3 to 8 decoder, as a data director. Use G1 as high enable and G2A + G2B as data input, D10. Signals A, B, and C will select which output follows D10. The three selector pins can be driven by direct PORTx commands setting the logic simultaneously. With D10 and three more pins as output, you can now select one of eight SPI devices.