ZOE-M8 series - Hardware integration manual
UBX-16030136 - R09
Design-in
Page 10 of 34
Production information
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For more information about supported SQI flash devices, see section A.3.
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Make sure that the SAFEBOOT_N pin is available for entering safe boot mode. Programming the
SQI flash memory with a flash firmware is done typically at production. For this purpose, the ZOE-
M8 GNSS SiPs must enter the safe boot mode. For more information about SAFEBOOT_N pin, see
section 2.6.
2.3
I/O pins
All I/O pins make use of internal pull-ups to VCC. Thus, there is no need to connect unused pins to
VCC.
2.3.1
Time pulse
A configurable time pulse signal is available with the ZOE-M8 GNSS SiPs.
The TIMEPULSE output generates pulse trains synchronized with GPS or UTC time grid with intervals
configurable over a wide frequency range. Thus, it may be used as a low frequency time
synchronization pulse or as a high frequency reference signal.
By default, the time pulse signal is configured to 1 pulse per second. For more information, see the u-
blox 8 / u-blox M8 Receiver Description including Protocol Specification [2].
2.3.2
External interrupt
EXTINT is an external interrupt pin with fixed input voltage thresholds with respect to VCC (see the
ZOE-M8 Data sheet
[1] for more information). It can be used for wake-up functions in power save
mode on all u-blox M8 SiPs and modules and for aiding, leave open if unused. By default, the external
interrupt is disabled.
If the EXTINT is not used for an external interrupt function, it can be used for some other purpose, for
example, as an output pin for the TXD Ready feature to indicate that the receiver has data to transmit.
For further information, see the u-blox 8 / u-blox M8 Receiver Description Including Protocol
Specification [2].
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If the EXTINT is configured for on/off switching of the ZOE-M8 GNSS SiPs, the internal pull-up
becomes disabled. Therefore ensure that the EXTINT input is always driven within the defined
voltage level by the host.
2.3.3
External LNA enable
LNA_EN pin can be used to turn on and off an external LNA. The external LNA will be turned off in
power save mode in on/off operation in OFF stage, or in software backup mode the external LNA will
also be turned off.
2.3.4
Electromagnetic interference and I/O lines
Any I/O signal line (length > ~3 mm) can act as an antenna and may pick up arbitrary RF signals
transferring them as noise into the GNSS receiver. This specifically applies to unshielded lines, lines
where the corresponding GND layer is remote or missing entirely, and lines close to the edges of the
printed circuit board. If for example, a cellular signal radiates into an unshielded high-impedance line,
it is possible to generate noise in the order of volts and not only distort receiver operation but also
damage it permanently.
On the other hand, noise generated at the I/O pins will emit from unshielded I/O lines. Receiver
performance may be degraded when this noise is coupled into the GNSS antenna (see Figure 17).
