ZOE-M8B - System Integration Manual
UBX-17045131 - R04
Contents
Page 20 of 42
Production Information
Figure 15: Active antenna supply circuit
2.6
Safe Boot Mode (SAFEBOOT_N)
If the
SAFEBOOT_N
pin is “low” at start up, the ZOE-M8B GNSS SiP starts in Safe Boot Mode and
does not begin GNSS operation. In Safe Boot Mode the SiP runs from an internal LC oscillator and
starts regardless of any configuration provided by the configuration pins. Thus, it can be used to
recover from situations where the SQI Flash has become corrupted.
For communication by UART in Safe Boot Mode, a training sequence (0x 55 55 at 9600 baud) can be
sent by the host to the ZOE-M8B GNSS SiP in order to enable communication. After sending the
training sequence, the host has to wait for at least 2 ms before sending messages to the receiver. For
further information see the
u-blox 8 / u-blox M8 Receiver Description Including Protocol Specification
Safe Boot Mode is used in production to program the SQI Flash. It is recommended to have the
possibility to pull the
SAFEBOOT_N
pin “low” when the SiP starts up. This can be provided using an
externally connected test point or via a host CPUs digital I/O port.
2.7
System Reset (RESET_N)
The ZOE-M8B GNSS SiP provides a RESET_N pin to reset the system. The RESET_N is an input-only
with internal pull-up resistor. It must be at low level for at least 10 ms to make sure RESET_N is
detected. It is used to reset the system. Leave RESET_N open for normal operation. The RESET_N
complies with the
VCC
level and can be actively driven high.
☞
RESET_N
should be only used in critical situations to recover the system. The Real-Time Clock
(RTC) will also be reset and thus immediately afterwards the receiver cannot perform a Hot Start.
☞
In reset state, the SiP consumes a significant amount of current. It is therefore recommended to
use
RESET_N
only as a reset signal and not as an enable/disable.
