User's Manual

LTE Module Series
EC21 Hardware Design
EC21_Hardware_Design Confidential / Released 30 / 94
The following figure shows the connection between the module and the host.
Figure 4: Sleep Mode Application withUSB Remote Wakeup
 Sending data to EC21through USB will wake up the module.
 When EC21has URC to report, the module will send remote wake-up signals via USB bus so as 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 wake-up function, the RI signal is
needed to wake up the host.
There are threepreconditions to let the module enter into the sleep mode.
 Execute AT+QSCLK=1 command to enable sleep mode.
 Ensure the DTR is held in high level or keep it open.
 The host’s USB bus, which is connected with the module’s USB interface, enters into suspended
state.