SIM900D Hardware Design
URC will be presented:
+CMTE:1
If the temperature < -30 , the fo
℃
llowing URC will be presented:
+CMTE:-1
The uncritical temperature range is -40 to
℃
+85 . If the temperature
℃
>+ 85 or
℃
< -40 , the module will be
℃
automatic shutdown soon.
If the temperature > +85 , the following URC will be presented:
℃
+CMTE:2
If the temperature <
-40
℃
, the following URC will be presented:
+CMTE:-2
After this moment, the AT commands can’t be executed. The module logs off from network and enters POWER
DOWN mode, and only the RTC is still active. POWER DOWN can also be indicated by STATUS pin, which is
a low level voltage in this mode.
To monitor the temperature, it can be used the “AT+CMTE” command to read the temperature when the module
is power on.
For details please refer to
document [1]
3.4.3 Restart SIM900D Using the PWRKEY Pin
User can restart SIM900D by driving the PWRKEY to a low level voltage for a short time and then release, the
same as turning on SIM900D using the PWRKEY pin. Before restarting the SIM900D, it need delay at least
500ms from detecting the STATUS low level on. The restarting scenario illustrates as the following figure.
Turn Off
Delay > 500ms
Restart
PWRKEY
STATUS
Figure10: Timing of restart system
3.5 Charging interface
SIM900D has integrated a charging circuit inside the module for Li-Ion batteries charging control, which make it
very convenient for applications to manage their battery charging. A common connection is shown in the
following figure:
SIM900D_HD_V1.02
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