Sleep Mode; Wake Up Module From Sleep Mode - Quectel M35 User Manual

If the module is set to minimum functionality by ―AT+CFUN=0‖, the RF function and SIM card function
would be disabled. In this case, the UART port is still accessible, but all AT commands related with RF
function or SIM card function will be not available.
If the module has been set by the command with ―AT+CFUN=4‖, the RF function will be disabled, but the
UART port is still active. In this case, all AT commands related with RF function will be not available.
After the module is set by ―AT+CFUN=0‖ or ―AT+CFUN=4‖, it can return to full functionality by
―AT+CFUN=1‖.
For detailed information about ―AT+CFUN‖, please refer to the document [1].

3.5.2. SLEEP Mode

The SLEEP mode is disabled by default. You can enable it by ―AT+QSCLK=1‖. On the other hand, the
default setting is ―AT+QSCLK=0‖ and in this mode, the module cannot enter SLEEP mode.
When the module is set by the command with ―AT+QSCLK=1‖, you can control the module to enter or exit
from the SLEEP mode through pin DTR. When DTR is set to high level, and there is no on-air or hardware
interrupt such as GPIO interrupt or data on UART port, the module will enter SLEEP mode automatically.
In this mode, the module can still receive voice, SMS or GPRS paging from network, but the UART port
does not work.

3.5.3. Wake Up Module from SLEEP Mode

When the module is in the SLEEP mode, the following methods can wake up the module.

If the DTR Pin is set low, it would wake up the module from the SLEEP mode. The UART port will be
active within 20ms after DTR is changed to low level.

Receiving a voice or data call from network will wake up the module.

Receiving an SMS from network will wake up the module.
NOTE
DTR pin should be held at low level during communication between the module and DTE.
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