Document : CS-SUP-MUTI-WPORTAPP-E02.sxw
3.1.2 - Wake Up and synchronization mechanism
In the purpose to optimize power consumption, the Wavecard is in a STANDBY mode and is wakening up
periodically to poll a radio activity. The wakeup period is given by the value of the AWAKENING_PERIOD
parameter, expressed in multiples of 100ms (1 second by default).
a) Principle when transmitting, or receiving a frame
When transmitting a frame to a distant equipment, the transmitter begins an awakening preamble called
'WakeUp' being used to awake the receiving equipments which will position then in radio reception. This
preamble results in the sending on the radio medium, of a binary succession of symbol.
This awakening preamble (WakeUp) can be of two types,
Long WakeUp
: used when transmitting a request towards distant equipment. Its duration can be
parameterized by the user (1100ms by default); and is generally equal to the WakeUp period of
the equipment to address, plus 100ms, in order to avoid transmitting between two periods of
reception.
Short WakeUp
: used only when responding to a point-to-point request. Its duration is equal to
50ms, and cannot be configured.
NUM
DESCRIPTION
VALUE
SIZE (in
bytes)
0x00
AWAKENING_PERIOD :
polling period of RF medium radio, in
multiples of 100ms
Period in multiples of 100ms
(by default, 0x0A for one second)
0 = quasi-permanent reception (every 20ms)
1
0x01
WAKEUP_TYPE :
Wake Up type used during a frame emission
0 : long Wake Up (default setting)
1 : short Wake Up = 50 ms
1
0x02
WAKEUP_LENGTH : duration of the Wake up when long wake
up is set up.
This value must be higher than the polling period of RF medium
radio.
Value in multiples of 1ms, defined LSB first
Default value : 1100 ms
min value = 20 ms (0x1400)
max value = 10 sec. (0x1027)
2
The receiver of the exchange, when it detect WakeUp preamble on the radio medium, carries out the
following operations:
It starts a timeout of waiting for the synchronization word (sync), which the duration is slightly
higher than its WakeUp period. This duration cannot be configured.
It begins a validation phase of the WakeUp preamble (detection of WakeUp). This phase
corresponds to the detection of several successive symbols composing the preamble. If the
detection fails, the equipment is repositioned in stand-by mode. The time of detection depends on
the speed transmission used.
The periodic wakeup having to occur when waiting of synchronization, are memorized (in order to
preserve the periodicity), but not carried out.
At the end of the phase of WakeUp, the transmitter equipment send a sequence of synchronization, followed
by data to be transmitted.
WaveCard user handbook
page 17 of 67
