SIM802 Hardware Design
From GHOST MODE to NORMAL MODE
3.4.1.3 Turn on SIM802 using the RTC (Alarm mode)
Alarm mode is a power-on approach by using the RTC. The alert function of RTC makes the
SIM802 wakeup while the module power off. In alarm mode, SIM802 will not register to GSM
network and the software protocol stack is closed. Thus the parts of AT commands related with
SIM card and Protocol stack will not be accessible, and the others can be used as well as in
normal mode.
Use the AT+CALARM command to set the alarm time. The RTC remains the alarm time if
SIM802 is power down by “AT+CPOWD=1” or by PWRKEY Pin. Once the alarm time expired
and executed, SIM802 will go into the Alarm mode. In this case, SIM802 will send out an
Unsolicited Result Code (URC) when set as fixed baud rate:
RDY
ALARM MODE
During Alarm mode, use AT+CFUN command to query the status of software protocol stack; it
will return 0 which indicates that the protocol stack is closed. Then after 90s, SIM802 will power
down automatically. However, during Alarm mode, if the software protocol is started by
AT+CFUN=1 command, the process of automatic power down will not be available. In ALARM
mode, driving the PWRKEY to a low level voltage for a period time will cause SIM802 to be
powered down. (Please refer to the power down scenarios).
The table follow briefly summarizes the AT commands that are used usually during alarm mode,
for details of the instructions refer to
document [1]
:
Table 7: AT commands used in Alarm mode
AT command
Use
AT+CALARM
Set alarm time
AT+CCLK
Set data and time of RTC
AT+CPOWD
Power down
AT+CFUN
Start or close the protocol stack
3.4.2 Turn off SIM802
Following procedure can be used to turn off the SIM802:
z
Normal power down procedure: Turn off SIM802 using the PWRKEY Pin
z
Normal power down procedure: Turn off SIM802 using AT command
z
Under-voltage and over-voltage automatic shutdown: Take effect if under-voltage or
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