User's Manual

LTE Module
EC20 Hardware Design
EC20_Hardware_Design Confidential / Released 25 / 83
3.5.1.3. USB Application with USB Suspend/Resume and RI Function
If host supports USB suspend/resume, but does not support remote wake-up function, the RI signal is
needed to wake up the host. The following part will show the sleep application.
There are three preconditions to let the module enter into the sleep mode.
 Execute AT command AT+QSCLK=1 to enable the 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 USB interface enters into suspended state.
The following figure shows the connection between the module and host.
USB_VBUS
USB_DP
USB_DM
AP_READY
VDD
USB_DP
USB_DM
GPIO
Module Host
GND
GND
RI
EINT
Figure 5: Sleep Application with RI
 Sending data to EC20 through USB will wake up the module.
 When EC20 has URC to report, RI signal will wake up the host.
3.5.1.4. USB Application without USB Suspend Function
If host does not support USB suspend function, you should disconnect USB_VBUS with additional control
circuit to let the module enter into sleep mode.
 Execute AT command AT+QSCLK=1 to enable the sleep mode.
 Ensure the DTR is held in high level or keep it open.
 Disconnect USB_VBUS.