User's Manual
Table Of Contents
- Contents
- Figures
- Tables
- 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 / Released
s
XT55/56_hd_v02.06a Page 76 of 125 17.12.2004
4.6 Serial interfaces of the XT55/56 GPS part
The GPS part of the XT55/56 module offers two serial interfaces:
SD1
• 2-wire serial interface
• Includes the SDI1 (receive) and SDO1 (transmit) lines
• Supported baud rate: 9600…115200 bps. See also [1] for details on the used GPS
protocol.
SD2
• 2-wire serial interface
• Includes the SDI2 (receive) and SDO2 (transmit) lines. It is intended for communication
with the GSM/ GPRS part of the XT55/56 module. See Figure 1 for details.
• Supported baud rate: 9600…115200 bps. See also [1] for details on the used GPS
protocol.
SD1 and SD2
• Both interfaces are configured for 8 data bits, no parity and 1 stop bit
• For more detailed characteristics see [1]
4.7 GPS control signals
GPS_M-RST:
This pin provides an active-low reset input to the board. It causes the board
to reset and start searching for satellites. Reset is an optional input and, if
not utilized, it may be left open.
GPS_BOOTSEL:
Set this pin to high for reprogramming the flash of the XT55/56 GPS part (for
instance updating to a new XT55/56 GPS firmware).
GPS_RFPC0, GPS_RFPC1 (including pull-up resistors):
These pins are input pins for Trickle-Power mode control. To use the Trickle-
Power mode function connect the RFPC0 and RFPC1 as shown in Figure
58. The pull-up resistors ensure the correct voltage level during start-up and
reset procedure of the GPS base band processor.
GPS_GPIO8, GPS_GPIO4:
These pins are control outputs for the Trickle-Power mode. GPS_GPIO8
must be connected to GPS_RFPC0 and GPS_GPIO4 to GPS_RFPC1.
GPS_GPIO8, GPS_GPIO4 can also be used to control a LED. A possible
circuit is shown in Figure 29. If the LED lights permanently the GPS receiver
is searching for satellites. If the GPS receiver is in Trickle-Power mode, the
LED flashes in rhythm, i.e. the GPS receiver receives valid position data.
Timing differs between GPS_GPIO4 and GPS_GPIO8.
Note: If Trickle power is switched off the LED lights permanently.