GSM/GPRS Module Series
M35 User Manual
M35_User_Manual Confidential / Released 27 / 85
It is suggested to control the module’s main power supply (VBAT) via LDO enable pin to restart the
module when the module has become abnormal. Power switch circuit like P-channel MOSFET switch
circuit can also be used to control VBAT.
3.3.4. Monitor Power Supply
The command ―AT+CBC‖ can be used to monitor the supply voltage of the module. The unit of the
displayed voltage is mV.
For details, please refer to the document [1].
3.4. Power On and Down Scenarios
3.4.1. Power On
The module can be turned on by driving the pin PWRKEY to a low level voltage. An open collector driver
circuit is suggested to control the PWRKEY. A simple reference circuit is illustrated as below.
Turn on pulse
PWRKEY
4.7K
47K
Figure 6: Turn On the Module with an Open-collector Driver
1. M35 module is set to autobauding mode (AT+IPR=0) by default. In the autobauding mode, URC
―RDY‖ is not reported to the host controller after module is powered on. When the module is powered
on after a delay of 4 or 5 seconds, it can receive AT command. Host controller should first send an
―AT‖ or ―at‖ string in order that the module can detect baud rate of host controller, it should continue to
send the next ‖AT‖ string until receiving ―OK‖ string from the module. Then enter ―AT+IPR=x;&W‖ to
set a fixed baud rate for the module and save the configuration to flash memory of the module. After
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