Quectel EG91 Series Hardware Design page 35

 Sending data to EG91 series module through USB will wake up the module.
 When EG91 series module has a URC to report, the module will send remote wakeup signals via
USB bus to wake up the host.
3.5.1.3. USB Application with USB Suspend/Resume and RI Function
If the host supports USB suspend/resume, but does not support remote wakeup function, the RI signal is
needed to wake up the host.
There are three preconditions to let the module enter sleep mode.
 Execute AT+QSCLK=1 to enable sleep mode.
 Ensure the DTR is held at high level or keep it open.
 The host's USB bus, which is connected with the module's USB interface, enters suspended state.
The following figure shows the connection between the module and the host.
 Sending data to EG91 series module through USB will wake up the module.
 When module has a URC to report, RI signal will wake up the host.
3.5.1.4. USB Application without USB Suspend Function
If the host does not support USB suspend function, USB_VBUS should be disconnected with an external
control circuit to let the module enter sleep mode.
 Execute AT+QSCLK=1 to enable sleep mode.
 Ensure the DTR is held at high level or keep it open.
 Disconnect USB_VBUS.
EG91_Series_Hardware_Design
Figure 5: Sleep Mode Application with RI
LTE Standard Module Series
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