Operation
INSYS GPRS mini
5
Operation
5.1
Switching ON the modem
There are two ways to switch on the modem, once power is applied:
• assert TO_IN to high level for > 1s
• activate the RS232 control line DTR
The modem is fully operational after 4 seconds. Logging onto a network may
take longer than this and is outside the control of the modem. The modem
can be configured to start up at the time power is applied by permanently
tying power connector signals TO_IN (pin 4) and VCC (pin 1) together. In this
case DTR must be used to switch the modem on again after it has been
switched off or reset, while power is still applied.
Note: DTR must be cycled from low to high.
Note: The TO_IN signal requires a positive “edge” (a sharp” signal transition
from low to high) to turn the modem on. This transition should be a rising
signal from 0V (GND) to VCC, or at least a large fraction of that voltage
range, and must be applied at the same time as VCC or after it. Very slow
transitions (significantly slower than many milliseconds) or very small transi-
tions (e.g. only few volts instead of 0V to VCC) will not turn on the module
(since they are not considered to be a “positive edge”).
Although this will not be an issue in almost all typical applications of the
modem, please consider following points:
Large capacitors in your power supply which will lead to slow leading
and falling edges (issue does not apply with modern stabilized switch-
ing regulator power-adaptors) AND TO_IN tied in parallel to VCC (in-
stead of separate dedicated digital signal)
Slow analogue signals used to assert TO_IN
TO_IN signal not before VCC
All 3 cases above might prevent the modem from recognizing the power-up
signal this is no failure of the modem itself, the same would apply to almost
any electronic device that provides a separate “power-on” or “reset” signal.
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