M20 Hardware Design
will return 0 which indicates that the protocol stack is closed. After 90 seconds, the module will
power down automatically. However, if the GSM protocol stack is started by “AT+CFUN=1”
command during the alarm mode, the process of automatic power-off will not be executed. In
alarm mode, driving the PWRKEY to a low level voltage for a period will cause the module to
power down (Please refer to the
power down chapter).
Table 8 briefly summarizes the AT commands that are frequently used during alarm mode, for
detail of these instructions please refer to
document [1]
:
Table 8: AT commands used in alarm mode
AT command
Function
AT+QALARM
Set alarm time
AT+CCLK
Set data and time of RTC
AT+QPOWD
Power down the module
AT+CFUN
Start or close the protocol stack
3.4.2 Turn off
The following procedure can be used to turn off the module:
z
Normal power down procedure: Turn off module using the PWRKEY pin
z
Normal power down procedure: Turn off module using command “AT+QPOWD”
z
Over-voltage or under-voltage automatic shutdown: Take effect when over-voltage or
under-voltage is detected
z
Emergent power down procedure: Turn off module using the EMERG_OFF pin
3.4.2.1 Turn off module using the PWRKEY pin (Power down)
Customer’s application can turn off the module by driving the PWRKEY to a low level voltage for
certain time. The power-down scenario illustrates as in Figure 8.
The power-down procedure causes the module logoff from the network and allow the software to
save important data before completely disconnecting the power supply, thus it is a safe way.
Before the completion of the power-down procedure the module sends out the result code shown
below:
NORMAL POWER DOWN
After this moment, no further AT command can be executed. And then the module enters the
POWER DOWN mode, only the RTC is still active. The POWER DOWN mode can also be
indicated by VDD_EXT pin, which is a low level voltage in this mode.
M20_HD_V1.01
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