Specifications

TC35 / TC37 Hardware Interface Description
TC35_37_HD_02_V03.10 - Released Page 28 of 92 21.12.2001
What to do if software controlled charging does not start up?
If the battery voltage fails to pass the 3.2V level when the 60 minutes timer expires,
processor controlled charging does not begin. To solve the problem you can do one of the
following:
• Once the voltage has reached its minimum of 3V, you can try to start software controlled
charging by pulling the IGT line to ground.
• If the voltage is still below 3V, driving the IGT line to ground switches the timer off and,
thus, prevents the system from proceeding to software controlled charging. Instead, you
are required to shortly disconnect and reconnect the charger. This turns on the timer and
starts anew the entire process.
Apart from this, trickle charging continues whenever the charger connects to the POWER
lines.
3.2.2.3 Operating modes during charging
Of course, the battery can be charged regardless of the engine's operating mode. When the
GSM engine is in Normal mode (SLEEP, IDLE or TALK mode), it remains operational while
charging is in progress (provided that sufficient voltage is applied). The charging process
during the Normal mode is referred to as Charge mode.
If the charger is connected to the POWER lines while the engine is in Power Down mode
(caused by AT^SMSO), the GSM engine goes into Charge-only mode.
How to activate mode Advantages
Charge mode
Connecting charger to the POWER lines
while GSM engine is
• operating, e.g. in IDLE or TALK mode
• in SLEEP mode
• Battery can be charged while GSM engine
remains operational and registered to the
GSM network.
• In IDLE and TALK mode, the RS-232 interface
is accessible. AT command set can be used
to full extent.
• In SLEEP mode, the RS-232 interface is not
accessible at all.
Charge-only mode
Connecting charger to the POWER lines
while GSM engine is
• in Power Down mode (powered down
by AT^SMSO)
• in Normal mode: Connect charger to
POWER lines, then enter AT^SMSO.
IMPORTANT: While trickle charging is in
progress, be sure that the application is
switched off. If the application is fed from
the trickle charge current the module
might be prevented from proceeding to
software controlled charging since the
current would no be sufficient.
• Battery can be charged while GSM engine is
deregistered from GSM network.
• Charging runs smoothly due to constant
current consumption.
• The AT interface is accessible and allows to
use the commands listed below.
Features of the Charge-only mode
Once the GSM engine enters the Charge-only mode, the AT command interface presents an
Unsolicited Result Code which reads:
^SYSSTART CHARGE-ONLY MODE
Note that this URC will not appear when autobauding was activated (due to the missing