Sleep modes
AP Associated Sleep mode
XBee Wi-Fi RF Module User Guide
53
AP Associated Sleep mode
This option allows the device to sync up with beacons sent from the Access Point (AP) which contains
the Delivery Traffic Indication Message (DTIM). The DTIM indicates when broadcast and multicast data
is sent on the network. This property is configured on the AP and is typically configured as the number
of beacons between each beacon with DTIM.
The current draw in Associated Sleep mode varies significantly. When the device is awake it draws
approximately 100 mA. When it is asleep, it draws approximately 2 mA. Total current draw increases
when the DTIM rate is higher and it decreases when the DTIM rate is lower on the access point.
The sleep modes described in this user guide have this option enabled.
Pin Sleep mode
UART data can be received in pin sleep mode, whether or not the host asserts the SLEEP_RQ pin. For
example, if RF data is received by the device while SLEEP_RQ is asserted, the device wakes up long
enough to send the data out the UART and then immediately resumes sleeping. If wake host is
configured, the device asserts the appropriate I/O lines (indicating that it is awake), then waits for
wake host timer to expire, then outputs the data, and then immediately resumes sleeping.
In this mode, when SLEEP_RQ is asserted the device powers down the Wi-Fi circuitry. When SLEEP_RQ
is de-asserted, the Wi-Fi circuitry is powered up. This causes the device to associate to the access
point for each wake event. If the device was associated when it went to sleep, it should be ready to
transmit data as soon as the ON_SLEEP pin indicates that the device is awake. If the device was not
associated when it went to sleep, the host must wait until the device is associated before a
transmission can occur. In API mode, a modem status frame is received when the device becomes
associated. Outside of API mode, the
AI
command must be used to determine when the device is
associated.
SPI operation is similar except that the device asserts ATTN when data becomes available and then
the local host is expected to assert SPI_SSEL and to provide a clock until the data available is sent out.
When the local UART host needs to send data it de-asserts SLEEP_RQ. Once the appropriate status
I/O lines are asserted (CTS and/or ON_SLEEP) the device is ready to accept data. However data will
be queued and not sent until the next DTIM.
When the local SPI host needs to send data it asserts SPI_SSEL. If SPI_SSEL is being used for pin sleep,
asserting SPI_SSEL is enough to awaken the device to receive the incoming data. But, if SLEEP_RQ is
being used to control sleep, then SPI_SSEL must be asserted and SLEEP_RQ must be de-asserted to
awaken the device to receive the data. This wakes up the device, which then accepts the incoming
data; however, data is queued and not sent until the next DTIM.
Cyclic Sleep mode
The device remains associated to the Access Point (AP) and sleeps based on the
parameter. After
SP
expires, the device wakes for 30 milliseconds to check for data from the AP and
to allow the host to send data or commands. This time is factored in as part of the overall
ST
time.
When data is received or sent within 30 ms, the device remains awake for
ST
time and any further
activity does not restart this time. When no data is received or sent within 30 ms, the device resumes
sleep immediately, without waiting for
ST
time-out.
Deep Sleep (Non-Associated Sleep) mode
This option allows the Wi-Fi circuitry to be powered down resulting in the lowest sleep current (about
6 µA) but at the expense of losing packets received during the time the device is asleep. This is
