NEO-M9N - Integration manual
If the Force-OFF (
EXTINTBACKUP
) feature in CFG-PM is enabled, the receiver will enter Inactive states
for as long as the configured EXTINT pin is set to 'low' until the next wake-up event. Any wake-up
event can wake up the receiver even while the EXTINT pin is set to 'low' (see
). However, if the
pin stays at 'low' state, the receiver will only wake up for the time needed to read the configuration
pin settings, then it will enter the Inactive state again.
If both Force-ON and Force-OFF features are enabled at the same time, the receiver PSM operation
will be completely in user's control. Setting 'high' on the configured EXTINT pin will wake up the
receiver to get a position fix and setting 'low' will put the receiver into sleep/backup mode.
3.11.2.2.11 Grid offset (GRIDOFFSET)
Once the receiver has a valid time, the update grid is aligned to the start of the week of the
(midnight between Saturday and Sunday). Before having a valid time, the update grid
is unaligned. A grid offset shifts the update grid with respect to the start of the week of the
. An example of usage can be found in section
The grid offset is not used in cyclic tracking operation.
3.11.2.3 Features
3.11.2.3.1 Communication
When PSM is enabled, communication with the receiver (e.g. UBX message to disable PSM) requires
particular attention. This is because the receiver may be in
Inactive
state and therefore unable
to receive any message through its interfaces. To ensure that the configuration messages are
processed by the receiver, even while in
Inactive
state, the following steps need to be taken:
• Send a dummy sequence of 0xFF (one byte is sufficient) to the receiver's UART interface.
This will wake up the receiver if it is in
Inactive
state. If the receiver is not in
Inactive
state, the
sequence will be ignored.
• Send the configuration message about half a second after the dummy sequence. If the interval
between the dummy sequence and the configuration message is too short, the receiver may
not yet be ready. If the interval is too long, the receiver may return to
Inactive
state before
the configuration message was received. It is therefore important to check for a UBX-ACK-
ACK reply from the receiver to confirm that the configuration message was received. The
configuration should be saved in a non-volatile layer (such as BBR or flash memory layer).
Similarly, when configuring the receiver for PSMOO (and PSMCT when
DONOTENTEROFF
is
disabled), ensure that the configurations are set in non-volatile layer. If they are not in a non-volatile
layer, the receiver will enter backup mode and when it wakes up again, it has lost the configuration
and has even forgotten it was in power save mode. This can be avoided if the key values of the
configuration items are saved into the BBR. If they are only saved into RAM, they will be lost after
the first backup entry (see
for details). When operating PSM from u-center
and setting the receiver to power save mode with CFG-PM-OPERATEMODE, check which layer the
setting is saved to.
3.11.2.3.2 Wake up
The receiver can be woken up by generating an edge on one of the following pins:
• rising or falling edge on one of the EXTINT pins
• rising or falling edge on the RXD pin
• rising edge on NRESET pin
All wake-up signals are interpreted as a position request, where the receiver wakes up and tries to
obtain a position fix. Wake-up signals have no effect if the receiver is already in
Acquisition
,
Tracking
or
POT
state.
UBX-19014286 - R07
3 Receiver functionality
Page 49 of 95
C1-Public
