Wireless SD Shield
Wireless SD Shield Front Wireless SD Shield Back
Overview
The Wireless SD shield al lows an Arduino board to communicate wirelessly using a wireless module. It is
based on the Xbee modules from Digi, but can use any module with the same footprint. The module can
communicate up to 100 feet indoors or 300 feet outdoors (with line-of-sight). It can be used as a
serial/usb replacement or you can put it into a command mode and configur e it for a variety of broadcast
and mesh networking options. The shields breaks out each of the Xbee's pins to a through-hole solder
pad.
Included on board is a SD card slot. When using the SD Library to access the card, Pin 4 is CS and cannot
be used otherwise. SPI also relies on pins 11, 12, and 13 for communication.
Also on board is a switch allowing for control via USB or the microcontroller.
Schematic
EAGLE files: arduino_WirelessShield_SD_v3-reference-design.zip
Schematic: arduino_WirelessShield_SD_v3-schematic.pdf
Switch Settings
The Wireless SD shield h a s an onboard switch labelled Micro and USB. This determine how the Xbee's
serial communication connects to the serial communication between the microcontroller (ATmega8 or
ATmega168) and USB-to-serial chip on the Arduino board.
When in the Micro position, the DOUT pin of the wireless module is
connected to the RX pin of the microcontroller; and DIN is connected to TX.
The wireless module will then commu nicate with the microcontroller. Not e
that the RX and TX pins of the microcontroller are still connect ed to the TX
and RX pins (respectively) of the USB-to-serial converter. Data sent from
the microcontroller will be transmitted to the computer via USB as well as
being sent wirelessly by the wireless module. The microcontroller will not be
programmable via USB in this mode.
With the switch in the USB position, the DOUT pin the wireless module is
connected to the RX pin of the USB-to-serial converter, and DIN on the
wireless module is connected to the TX pin of the USB-to-serial converter.
This means that the module can communicate directly with the computer.
The microcont roller on the board will be bypassed. To use the shield in
this mode, you must program the microcontroller with an empty
sketch (shown below), or remove it from the board.
Empty sketch:
void setup() { }
void loop() { }
[Get Code]
Networking
The Wireless SD shield can be used with different modules with the same footprint as the XBee modules.
The instructions below are for the XBee 80 2.15.4 modules (sometimes called "Series 1" t o distinguish
them from the Series 2 modules, although "Series 1" doesn't appear in the official name or product
description) and also for the XBee ZNet 2.5 or XBee ZB modules, both known as "Series 2" modules. All
the modules, basically have the same type of configuration parameters, but differ by the function that
they implement and the topologies of networks that they can create. Can communicate with each other
only modules of the same family.
Addressing
There are multiple parameters that need to be configured correctly for two modules to talk to each other
(although with the default settings, all modules should be able to talk to each other). They need to be on
the same network, as set by the ID parameter (see "Configuration" below for more details on the
parameters). The modules need to be on the same channel, as set by the CH parameter. Finally, a
module's destination address (DH and DL parameters) determine which modules on its network and
channel will receive the data it transmits. This can happen in a few ways:
If a module's DH is 0 and its DL is less than 0xFFFF (i.e. 16 bits), data transmitted by that module
will be received by any module whose 16-bit address MY parameter equals DL.
If DH is 0 and DL equals 0xFFFF, the module's transmissions will be received by all modules.
If DH is non-zero or DL is greater than 0xFFFF, the transmission will only be received by the
module whose serial number equals the transmitting module's destination address (i.e. whose SH
equals the transmitting module's DH and whose SL equals its DL).
Again, this address match ing will only happen between modules on the sa me network and channel. If two
modules are on different networks or channels, they can't communicate regardless of their addresses.
For the "Series 2" modules you must chose which firmware put on the module to give it Coordinator,
Router or End Device fun ct ion ality. Series 2 use on ly serial low (SL) and serial high (SH) for addressi ng.
Configuration
Here are some of the more useful parameters for configuring your Xbee module. For step-by-step
instructions on reading and writ ing them using AT commands, see the:
guide to the Wireless shield with the 802.15.4 modules.
guide to the Wireless shield with the ZNet 2.5 modules.
Make sure to prepend AT to the parameter name when sending a command to the module (e.g. to read
the ID parameter, you should send the command ATID).
Command
Description Valid Values Default Value
ID The network ID of the XBee module. 0 - 0xFFFF 3332
CH The channel of the XBee module. 0x0B - 0x1A 0X0C
SH and SL The serial number of the XBee module (SH gives the
high 32 bits, SL the low 32 bits). Read-only. 0 - 0xFFFFFFFF
(for both SH and SL)
different for each
module
MY The 16-bit address of the module. 0 - 0xFFFF 0
DH and DL The destination address for wireless communication
(DH is the high 32 bits, DL the low 32). 0 - 0xFFFFFFFF
(for both DH and DL)
0 (for both DH and
DL)
BD The baud rate used for serial communication with
the Arduino board or computer. 0 (1200 bps)
1 (2400 bps)
2 (4800 bps)
3 (9600 bps)
4 (19200 bps)
5 (38400 bps)
6 (57600 bps)
7 (115200 bps)
3 (9600 baud)
Note: although the valid and default values in the table above are written with a prefix of "0x" (to indicate
that they are hexadecimal numbers), the module will not includ e the "0x" when reporting the value of a
parameter, and you should omit it when setting values.
Here are a couple more useful commands for configuring the XBee module (you'll need to prepend AT to
these too).
Command
Description
RE Restore factory default settings (note that like
parameter changes, this is not permanent unless
followed by the WR command).
WR Write newly configured parameter values to non-
volatile (long-term) storage. Otherwise, they will
only last until th e module loses power.
CN Exit command mode now. (If you don't send any
commands to the module for a few seconds,
command mode will timeout and exit even without a
CN command.)
For more details on configuring the XBee module, see the 802.15.4 modules product manual or the ZB
modules product manual from Digi International.
