User Manual

XBee® Wi-Fi RF Modules

incoming data. But, if SleepRq is being used to control sleep, then SPI_nSSEL must be

asserted and SleepRq must be de-asserted to awaken the module to receive the data.

This wakes up the module, which will then accept the incoming data. However data will

be queued and not sent until the next DTIM.

Cyclic Sleep Mode

The module remains associated to the AP and will sleep based on the SP parameter.

After SP expires, the module will awaken 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 module will remain

awake for ST time and any further activity will not restart this time. When no data is

received or sent within 30 ms, the module will resume sleeping immediately, without

waiting for ST time-out.

Deep Sleep (Non-Associated Sleep)

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

module is asleep. This is because the access point will behave like the module is in full

power mode while it is asleep and it will not hold back packets until the module wakes

up.

Pin Sleep Mode

In this mode when SleepRq is asserted the module will power down the Wi-Fi circuitry.

When SleepRq is de-asserted the Wi-Fi circuitry is powered up. This causes the module

to associate to the access point for each wake event. If the module was associated

when it went to sleep, it should be ready to transmit data as soon as the module

indicates that it is awake, which occurs within one millisecond of the pin wake up

. If

not, a new association could take much longer to complete, especially if DHCP is used.

Cyclic Sleep Mode

In this mode the module will enter and exit sleep based on the SP, ST, and SA

commands. SP specifies the sleep time and ST specifies the wake time of the module

after it is associated. SA specifies the maximum time to wait for association before

starting the ST timer. If SA expires before the association process completes, then the

module will sleep anyway. When it awakens from this state, then it will start the SA

timer again to seek to establish association.

Under normal conditions, SA is used for a time out for the first association following

reset and ST is used for short wake cycles thereafter. To conserve battery power, SA

should be long enough for association and ST should be as short as possible for the

application.

Sampling Data Using Sleep Modes

Data can be sampled when waking from any sleep mode by enabling an ADC or digital

input and setting IR appropriately with respect to ST to obtain the desired number of

samples.