User Manual
Table Of Contents
- Document History
- Introduction
- Product Concept
- GSM Application Interface
- GSM/GPRS Operating Modes
- Power Supply
- Power Up / Down Scenarios
- Automatic GPRS Multislot Class Change
- Charging Control of the GSM Part
- Power Saving
- Summary of State Transitions (Except SLEEP Mode)
- RTC Backup for GSM Part of XT55/56
- Serial Interfaces of the XT55/56 GSM Part
- Audio Interfaces
- SIM Interface
- Control Signals
- GPS Application Interface
- GSM and GPS Antenna Interfaces
- Electrical, Reliability and Radio Characteristics
- Mechanics
- Reference Approval
- Example Applications
- List of Parts and Accessories
XT55/56 Hardware Interface Description
Confidential / Preliminary
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XT55/56_hd_v02.96 Page 49 of 125 18.08.2005
Features of Charge-only mode
Once the GSM engine enters the Charge-only mode, the AT command interface presents an
Unsolicited Result Code (URC) which reads:
^SYSSTART CHARGE-ONLY MODE
Note that this URC will not appear when autobauding was activated (due to the missing
synchronization between DTE and DCE upon start-up). Therefore, it is recommended to
select a fixed baudrate before using the Charge-only mode.
While the Charge-only mode is in progress, you can only use the AT commands listed in
Table 10. For further instructions refer to the AT Command Set supplied with your GSM
engine.
Table 10: AT commands available in Charge-only mode
AT command Function
AT+CALA Set alarm time
AT+CCLK Set date and time of RTC
AT^SBC Monitor charging process
Note: While charging is in progress, no battery capacity value is available. To query
the battery capacity disconnect the charger.
If the charger connects externally to the host device no charging parameters are
transferred to the module. In this case, the command cannot be used.
AT^SCTM Query temperature range, enable/disable URCs to report critical temperature
ranges
AT^SMSO Power down GSM engine
To proceed from Charge-only mode to normal operation, it is necessary to drive the ignition
line to ground. This must be implemented in your host application as described in Chapter
3.3.1.1. See also Chapter 3.7 which summarizes the various options of changing the mode of
operation.
If your host application uses the GSM_SYNC pin to control a status LED as described in
Chapter 3.12.2.2, please note that the LED is off while the GSM engine is in Charge-only
mode.
3.5.5 Charger Requirements
If you are using the implemented charging technique and the charging circuit recommended
in Figure 8, the charger must be designed to meet the following requirements:
a) Simple transformer power plug
- Output voltage: 5.5V...8V (under load)
- The charge current must be limited to 500mA
- Voltage spikes that may occur while you connect or disconnect the charger must be
limited.
- There must not be any capacitor on the secondary side of the power plug (avoidance of
current spikes at the beginning of charging)
b) Supplementary requirements for a) to ensure a regulated power supply
- When current is switched off a voltage peak of 10V is allowed for a maximum 1ms
- When current is switched on a spike of 1.6A for 1ms is allowed