GSM/GPRS Module
M85 Hardware Design
M85_Hardware_Design Confidential / Released 27 / 92
3.3.4. Monitor Power Supply
To monitor the supply voltage, customer can use the ―AT+CBC‖ command which includes three
parameters: charging status, remaining battery capacity and voltage value (in mV). It returns the 0-100
percent of battery capacity and actual value measured between VBAT and GND. The voltage is
automatically measured in period of 5s. The displayed voltage (in mV) is averaged over the last
measuring period before the ―AT+CBC‖ command is executed.
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, and after STATUS pin
outputs a high level, PWRKEY pin can be released. Customer may monitor the level of the STATUS pin
to judge whether the module is power-on or not. 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
M85 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 receives AT command, it
will be powered on after a delay of 2 or 3 seconds. Host controller should first send an ―AT‖ or ―at‖ string in
order that the module can detect baud rate of host controller, and it should send the second or the third
NOTE
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