SARA-G3 and SARA-U2 series - System Integration Manual
UBX-13000995 - R26
System description
Page 58 of 217
Figure 30 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.
DCE UART is enabled for 2000 GSM frames (~9.2s)
after the last data received
time
Wake up time: ~20 ms
time
Wake up character
Not recognized by DCE
Valid characters
Recognized by DCE
OFF
ON
TXD input
UART
OFF
ON
Figure 30: Wake-up via data reception with further communication
The “wake-up via data reception” feature cannot be disabled.
In command mode
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, if autobauding is enabled and the DTE does not implement HW flow control, the
DTE must always send a character to the module before the “AT” prefix set at the beginning of each
command line: the first character is ignored if the module is in active mode, or it represents the wake-up
character if the module is in idle mode.
In command mode
, if autobauding is disabled, the DTE must always send a dummy “AT” before each
command line: the first character is not ignored if the module is in active mode (i.e. the module replies
“OK”), or it represents the wake up character if the module is in low power idle mode (i.e. the module
does not reply).
No wake-up character or dummy “AT” is required from the DTE during a voice or data call since the
module UART interface continues to be enabled and does not need to be woken-up. Furthermore in data
mode
a dummy “AT” would affect the data communication.
Additional considerations for SARA-U2 modules
SARA-U2 modules are forced to stay in active mode if the USB is connected and not suspended, and therefore
the AT+UPSV=1, AT+UPSV=2 or AT+UPSV=3 settings are overruled but they have effect on the UART behavior:
they configure UART interface power saving, so that UART is enabled / disabled according to the AT+UPSV=1,
AT+UPSV=2 or AT+UPSV=3 settings.
To set the AT+UPSV=1, AT+UPSV=2 or AT+UPSV=3 configuration over the USB interface of SARA-U2 modules,
the autobauding must be previously disabled on the UART by the +IPR AT command over the used AT interface
(the USB), and this +IPR AT command configuration must be saved in the module’ non-volatile memory (see the
u-blox AT Commands Manual
[3]). Then, after the subsequent module re-boot, AT+UPSV=1, AT+UPSV=2 or
AT+UPSV=3 can be issued over the used AT interface (the USB): all the AT profiles are updated accordingly.
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See the
u-blox AT Commands Manual
[3] for the definition of the command mode, data mode, and online command mode.
