The Arduino WiFi
Shield allows an Arduino board to connect to the internet using the 802.11 wireless specification (WiFi
). It is based on the HDG204
Wireless LAN 802.11b/g System in-Package. An AT32UC3
provides a network (IP) stack capable of both TCP and UDP. Use the WiFI library
to write sketches which connect to the internet using the shield. The WiFI
shield connects to an Arduino board using long wire-wrap headers which extend through the shield. This keeps the pin layout intact and allows another shield to be stacked on top.
Shield can connect to wireless networks which operate according to the 802.11b and 802.11g specifications.
There is an onboard micro-SD card slot, which can be used to store files for serving over the network. It is compatible with the Arduino Uno and Mega. The onboard microSD card reader is accessible through the SD Library. When working with this library, SS is on Pin 4.
Arduino communicates with both the Wifi shield's processor and SD card using the SPI bus (through the ICSP header). This is on digital pins 11, 12, and 13 on the Uno and pins 50, 51, and 52 on the Mega. On both boards, pin 10 is used to select the HDG204
and pin 4 for the SD card. These pins cannot be used for general I/O. On the Mega, the hardware SS pin, 53, is not used to select either the HDG204
or the SD card, but it must be kept as an output or the SPI interface won't work.
Digital pin 7 is used as a handshake pin between the WiFi
shield and the Arduino, and should not be used.
Note that because the HDG204
and SD card share the SPI bus, only one can be active at a time. If you are using both peripherals in your program, this should be taken care of by the corresponding libraries. If you're not using one of the peripherals in your program, however, you'll need to explicitly deselect it. To do this with the SD card, set pin 4 as an output and write a high to it. For the HDG204
, set digital pin 10 as a high output.
The shield can connect to encrypted networks that use either WPA2
Personal or WEP encryption. It can also connect to open networks.
A network must broadcast its SSID for the shield to be able to connect.
The previous version of this shield uses a HDG104
instead of the actual HDG204
On board interfaces
The reset button on the shield resets both the HDG204
and the Arduino board.
There is an onboard Mini-USB connector. This is not for programming an attached Arduino, it is for updating the AT32UC3
using the Atmel DFU protocol. The programming jumper adjacent to the power bus and analog inputs should be left unconnected for typical use. It is only used for DFU programming mode.
A FTDI connection enables serial communication with the 32U for debugging purposes. A list of available commands can be found here
On board indicators
The shield contains a number of informational LEDs
- L9 (yellow) : this is tied to digital pin 9
- LINK (green) : indicates a connection to a network
- ERROR (red) : indicates when there is a communication error
- DATA (blue) : indicates data being transmitted/received
Updating firmware on the shield
Please follow this guide
to update the firmware on your shield.
See also : getting started with the WiFi shield
and WiFi library reference