LARA-R2 series - System Integration Manual
UBX-16010573 - R02
Objective Specification
System description
Page 44 of 148
Wake up via data reception
The UART wake up via data reception consists of a special configuration of the module
TXD
input line that
causes the system wake-up when a low-to-high transition occurs on the
TXD
input line. In particular, the UART
is enabled and the module switches from the low power idle-mode to active-mode within ~20 ms from the first
character received: this is the system “wake up time”.
As a consequence, the first character sent by the DTE when the UART is disabled (i.e. the wake up character) is
not a valid communication character even if the wake up via data reception configuration is active, because it
cannot be recognized, and the recognition of the subsequent characters is guaranteed only after the complete
system wake-up (i.e. after ~20 ms).
The UART wake up via data reception configuration is active in the following cases:
AT+UPSV=1 is set with HW flow control disabled
Figure 20 and Figure 21 show examples of common scenarios and timing constraints:
AT+UPSV=1 power saving configuration is active and the timeout from last data received to idle-mode start
is set to 2000 frames (AT+UPSV=1,2000)
Hardware flow control is disabled
Figure 20 shows the case where the module UART is disabled and only a wake-up is forced. In this scenario the
only character sent by the DTE is the wake-up character; as a consequence, the DCE module UART is disabled
when the timeout from last data received expires (2000 frames without data reception, as the default case).
Wake up character
Not recognized by DCE
OFF
ON
DCE UART is enabled for 2000 GSM frames (~9.2 s)
time
Wake up time: ~20 ms
time
TXD input
UART
OFF
ON
Figure 20: Wake-up via data reception without further communication
Figure 21 shows the case where in addition to the wake-up character further (valid) characters are sent. The
wake up character wakes-up the module UART. The other characters must be sent after the “wake up time” of
~20 ms. If this condition is satisfied, the module (DCE) recognizes characters. The module will disable the UART
after 2000 GSM frames from the latest data reception.
Wake up character
Not recognized by DCE
Valid characters
Recognized by DCE
DCE UART is enabled for 2000 GSM frames (~9.2s)
after the last data received
time
Wake up time: ~20 ms
time
OFF
ON
TXD input
UART
OFF
ON
Figure 21: Wake-up via data reception with further communication
