Stacking Shields

form factor sizes can be plugged into Arduino MEGA 2560 boards. Those shields with the Arduino Uno form factor fit at the USB connector end of the MEGA 2560, using only the pins on this end of the board, and possibly the pins from the ICSP header in the middle of the board as well, as shown in Figure 1.6. Full-size shields that are the same size as the MEGA 2560 board are also available that connect to all of the pins on the MEGA 2560. Take note that not all small sized shields that work with Arduino Uno boards will work with Arduino MEGA 2560 boards, as is explained in the sections on the SPI bus in this manual, and in full detail in Chapter 9.

Figure 1.6: Arduino MEGA 2560 with Small Form Factor Ethernet Shield

Stacking Shields

Shields can be stacked one on top of the other to add multiple hardware functionality to an Arduino board. An example of a stack of shields is shown in Figure 1.7 on the next page. In this figure, a full-sized MEGA Proto shield is plugged into an Arduino MEGA 2560, and an Arduino Uno sized Ethernet shield is plugged into the MEGA Proto shield. The Ethernet shield is the small sized shield that fits both the Arduino MEGA 2560 and the Arduino Uno. This particular shield is compatible with both the Uno and MEGA 2560.

Stacking shields is only possible if the shields being used have long pinned connectors that provide pins at the bottom of the shield to plug into the board below, as well as sockets that allow a board to be plugged in above.