User's Manual

M50 Hardware Design
M50_HD_V2.0 - 32 -
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
Customer’s application 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 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 using driving circuit
Note: The module is set to autobauding mode (AT+IPR=0) in default configuration. In the
autobauding mode, the URC “RDY” after powering on is not sent to host controller. When the
module receives AT command, it will be powered on after a delay of 2 or 3 seconds. 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 UART Port of the module every
time when the module is powered on. Refer to the section “AT+IPR” in document [1].
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