M12 Hardware Design
M12_Hardware_Design_V3.3
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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 continuously measured at an interval depending on the operating mode. The displayed
voltage (in mV) is averaged over the last measuring period before the “AT+CBC” command is
executed.
For details please refer to
document [1]
.
3.4. Power up and power down scenarios
3.4.1. Power on module using PWRKEY pin
The module can be turned on through the PWRKEY pin. Customer can turn on the module by
driving the pin PWRKEY to a low level voltage and after STATUS pin outputs a high level,
PWRKEY pin can be released. Customer can monitor the level of the STATUS pin to judge
whether the module is power-on or not.
Note: The module is set to autobauding mode (AT+IPR=0) in default configuration. In the
autobauding mode, the URC “RDY” is not sent to host controller after powering on. AT
command can be sent to the module 2-3 seconds after the module is powered on. Host controller
should firstly 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 “AT” or “at” string until receiving “OK”
string from the module. Then an “AT+IPR=x;&W” should be sent to set a fixed baud rate for
the module and save the configuration to flash memory of the module. After these
configurations, the URC “RDY” would be received from the serial port of the module every
time when the module is powered on. Refer to Chapter “AT+IPR” in document [1].
An open collector driver circuit is suggested to control the PWRKEY. A simple reference circuit
is illustrated in Figure 6.
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