SimCom SIM808, Проектирование аппаратного обеспечения

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SIM808_Hardware Design_V1.00 2014.03.27 25
For detail about the AT command “AT+CPOWD”, please refer to
document [1]
4.2.2.3 Over-voltage or Under-voltage Power down
The module software monitors the VBAT voltage constantly.
If the voltage
≤ 3.5V, the following URC will be reported:
UNDER-VOLTAGE WARNNING
If the voltage ≥ 4.3V, the following URC will be reported:
OVER-VOLTAGE WARNNING
If the voltage < 3.4V, the following URC will be reported, and the module will be automatically powered down.
UNDER-VOLTAGE POWER DOWN
If the voltage > 4.4V, the following URC will be reported, and the module will be automatically powered down.
OVER-VOLTAGE POWER DOWN
At this moment, AT commands can not be executed any more, and only the RTC is still active. Power down mode
can also be indicated by STATUS pin, which is at low level at this time.
4.2.2.4 Over-temperature or Under-temperature Power down
The module will constantly monitor the temperature of the module,
If the temperature > +80
℃ , the following URC will be reported:
+CMTE: 1
If the temperature < -30 ℃ , the following URC will be reported:
+CMTE:-1
If the temperature > +85
℃
, the following URC will be reported, and the module will be automatically powered
down.
+CMTE: 2
If the temperature < -40 ℃ , the following URC will be reported, and the module will be automatically powered
down.
+CMTE:-2
At this moment, AT commands can not be executed any more, and only the RTC is still active. Power down mode
can also be indicated by STATUS pin, which is at low level at this time.
The AT command “AT+CMTE” could be used to read the temperature when the module is running.
For details please refer to
document [1].
4.2.3 Reset Function
SIM808 also has a RESET pin (pin 16) used to reset the module. This function is used as an emergency reset
only when AT command “AT+CPOWD=1” and the POWER_ON pin has no effect. User can pull the RESET pin
to ground, then the module will reset.
This pin is already isolated in the module, so the external isolation is not necessary. Following figure is internal
circuit of the RESET pin.