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MANUAL
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Figure 30: Phone Module, Power ON/OFF
Note:
For more information and precautions on module shutdown, see section 6.4 below.
4.2 Alarm
Application
Wakeup
The application can setup an alarm inside GM41 which will wakeup the phone-module at a specific time. This
feature makes use of the following signals:
•
VREF
•
VRTC
It furthermore requires the serial channel TD and RD to setup the real time clock (AT+CCLK) and the alarm time
(AT+CALA).
VREF:
The phone module reference voltage goes active high (0.8V to 2.0V) for 250ms when the alarm activates. The low-
to-high transition of this signal shall be used to wake up the application. The application then performs a normal
power up sequence.
VRTC:
The implementation of the real-time clock voltage (VRTC) can differ depending on the application:
•
In a cheap solution the application could apply 1.8V on VRTC using a regulator.
•
If low current consumption is required, the application could use a super-cap which would be charged by
the phone-module while it is operating, relying on the cap providing power when it is powered down.
•
If the application would wake up for short periods and stays powered down for long periods; the use of a
regulator might be required since the cap might not be able to sustain power.
Sequence:
1.
Alarm is activated. The phone-module output a high pulse (250ms) on VREF.
2.
The application has detected the positive pulse on VREF and enables both 5V power supplies and sets
MODULE_PWR_EN_B active low.
