Integration Manual

LISA-U2 series - System Integration Manual
UBX-13001118 - R25 System description Page 99 of 182
1.12 General Purpose Input/Output (GPIO)
LISA-U2 series modules provide up to 14 pins (GPIO1-14) which can be configured as general purpose
input or output, or can be configured to provide special functions via u-blox AT commands (for further
details, see the u-blox AT Commands Manual [2], +UGPIOC, +UGPIOR, +UGPIOW, +UGPS, +UGPRF,
+USPM).
The following functions are available in the LISA-U2 modules:
GSM Tx burst indication:
GPIO1 pin can be configured by AT+UGPIOC to indicate when a GSM Tx burst/slot occurs, setting the
parameter <gpio_mode> of AT+UGPIOC command to 9.
No GPIO pin is configured by default to provide the “GSM Tx burst indication” function.
The pin configured to provide the “GSM Tx burst indication” function is set as
 Output / High, since ~10 µ s before the start of first Tx slot, until ~5 µ s after the end of last Tx slot
 Output / Low, otherwise
The pin configured to provide the “GSM Tx burst indication” function can be connected on the
application board to an input pin of an application processor to indicate when a GSM Tx burst/slot
occurs.
GNSS supply enable:
The GPIO2 is by default configured by AT+UGPIOC command to enable or disable the supply of the u-
blox GNSS receiver connected to the cellular module.
The GPIO1, GPIO3, GPIO4 or GPIO5 pins can be configured to provide the “GNSS supply enable”
function, alternatively to the default GPIO2 pin, setting the parameter <gpio_mode> of AT+UGPIOC
command to 3. The “GNSS supply enable” 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 “GNSS supply enable” function is set as
 Output / High, to switch on the u-blox GNSS receiver, if the parameter <mode> of AT+UGPS
command is set to 1
 Output / Low, to switch off the u-blox GNSS receiver, if the parameter <mode> of AT+UGPS
command is set to 0 (default setting)
The pin configured to provide the “GNSS supply enable” function must be connected to the active-
high enable pin (or the active-low shutdown pin) of the voltage regulator that supplies the u-blox GNSS
receiver on the application board.
GNSS data ready:
Only the GPIO3 pin provides the “GNSS data ready” function, to sense when a u-blox GNSS receiver
connected to the cellular module is ready to send data via the DDC (I
2
C) interface, setting the
parameter <gpio_mode> of AT+UGPIOC command to 4.
The pin configured to provide the “GNSS data ready” function will be set as
 Input, to sense the line status, waking up the cellular module from idle mode when the u-blox GNSS
receiver is ready to send data via the DDC (I
2
C) interface; this is possible if the parameter <mode>
of AT+UGPS command is set to 1 and the parameter <GPS_IO_configuration> of AT+UGPRF
command is set to 16
 Tri-state with an internal active pull-down enabled, otherwise (default setting)
The pin that provides the “GNSS data ready” function must be connected to the data ready output of
the u-blox GNSS receiver (i.e. the pin TxD1 of the u-blox GNSS receiver) on the application board.