Usb Application With Usb Suspend/Resume And Ri Function; Usb Application Without Usb Suspend Function - Quectel EC21 Series Hardware Design

 Sending data to module via USB will wake up the module.
When module has a URC to report, the module will send remote wake-up 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 and resume, but does not support remote wake-up 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 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 suspend state.
The following figure shows the connection between the module and the host.
 Sending data to module via 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 via an
additional 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.
EC21_Series_Hardware_Design
Figure 5: Sleep Mode Application with RI
LTE Standard Module Series
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