Integration Manual

LISA-U2 series - System Integration Manual
UBX-13001118 - R25 System description Page 100 of 182
GNSS RTC sharing:
Only the GPIO4 pin provides the “GNSS RTC sharing” function to provide an RTC (Real Time Clock)
synchronization signal to the u-blox GNSS receiver connected to the cellular module, setting the
parameter <gpio_mode> of AT+UGPIOC command to 5.
The pin configured to provide the “GNSS RTC sharing” function will be set as
 Output, to provide an RTC (Real Time Clock) synchronization signal to the u-blox GNSS receiver if
the parameter <mode> of AT+UGPS command is set to 1 and parameter <GPS_IO_configuration>
of AT+UGPRF command is set to 32
 Output / Low, otherwise (default setting)
The pin that provides the “GNSS RTC sharing” function must be connected to the RTC
synchronization input of the u-blox GNSS receiver (i.e. the pin EXTINT0 of the u-blox GNSS receiver)
on the application board.
SIM card detection:
The GPIO5 pin is by default configured by AT+UGPIOC command to detect SIM card presence.
Only the GPIO5 pin can be configured to provide the “SIM card detection” function, setting the
parameter <gpio_mode> of the AT+UGPIOC command to 7 (default setting).
The pin configured to provide the “SIM card detection” function is set as
 Input with an internal active pull-down enabled, to sense SIM card presence
The pin must be connected on the application board to SW2 pin of the SIM card holder, which must
provide 2 pins for the mechanical card presence detection, with a 470 kΩ pull-down resistor. SW1 pin
of the SIM card holder must be connected to the V_INT pin of the module, by a 1 kΩ pull-up resistor.
See Figure 52 and section 1.8 for the application circuit. The GPIO5 signal will be pulled low by the pull-
down when a SIM card is not inserted in the holder, and will be pulled high by the pull-up when a SIM
card is present.
The GPIO5 pin is configured as an external interrupt to detect SIM card presence. An Unsolicited
Result Code (URC) can be generated each time that there is a change of status (for more details, see
the “simind” value of the <descr> parameter of +CIND and +CMER commands in the u-blox AT
Commands Manual [2]).
All LISA-U2 series modules provide the additional function “SIM card hot insertion/removal” on the
GPIO5 pin, which can be enabled using the AT+UDCONF=50 command (for more details, see the
u-blox AT Commands Manual [2]).
Network status indication:
GPIO1, GPIO2, GPIO3, GPIO4 or GPIO5 can be configured to indicate network status (i.e. no service,
registered home 2G network, registered home 3G network, registered visitor 2G network, registered
visitor 3G network, voice or data 2G/3G call enabled), setting the parameter <gpio_mode> of
AT+UGPIOC command to 2.
No GPIO pin is configured by default to provide the “Network status indication” function.
The “Network status indication” mode can be provided only on one pin at a time: it is not possible to
simultaneously set the same mode on another pin.
The pin configured to provide the “Network status indication” function is set as
 Continuous Output / Low, if no service (no network coverage or not registered)
 Cyclic Output / High for 100 ms, Output / Low for 2 s, if registered home 2G network
 Cyclic Output / High for 50 ms, Output / Low for 50 ms, Output / High for 50 ms, Output / Low for
2 s, if registered as a home 3G network