SIM900D Hardware Design
URC will be presented:
+CMTE:1
If the temperature < -30 , the
℃
following 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 not 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, you can used the “AT+CMTE” command to read the temperature when the module is
power on.
For details please refer to
related 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, user need delay at least
800ms from detecting the STATUS low level on. The restarting scenario illustrates as the following figure.
Figure11: Timing of restart SIM900D
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 which support battery charging. A common connection is shown in the following
figure:
SIM900D_Hardware Design_V1.04
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