u-blox NEO-M8U User Manual
performance
concurrent
NEO-M8U
u-blox M8 untethered dead reckoning module including
3D inertial sensors
Hardware integration manual
Abstract
This document describes the features and specifications of NEO-M8U, a highuntethered dead reckoning module with 3D sensors. The module includes the u-blox M8
GNSS engine with reception of GPS, GLONASS, BeiDou, Galileo and QZSS signals.
www.u-blox.com
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NEO-M8U - Hardware integration manual
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Document information
Title NEO-M8U
Subtitle u-blox M8 untethered dead reckoning module including 3D inertial sensors
Document type Hardware integration manual
Document number UBX-15016700
Revision and date R11 22-Mar-2021
Disclosure restriction C1-Public
Product status
In Development /
Prototype
Engineering Sample Advance Information Data based on early testing. Revised and supplementary data will be published later.
Initial Production Early Production Information Data from product verification. Revised and supplementary data may be published later.
Mass Production /
End of Life
Corresponding content status
Objective Specification Target values. Revised and supplementary data will be published later.
Production Information Document contains the final product specification.
European Union regulatory compliance
NEO-M8U compiles with all relevant requirements for RED 2014/53/EU. The NEO-M8U
Conformity (DoC) is available at www.u-blox.com within Support > Product resources > Conformity Declaration.
This document applies to the following products:
Product name Type number ROM/FLASH version PCN/IN reference
NEO-M8U NEO-M8U-0-10 Flash FW 3.01 UDR 1.00
NEO-M8U NEO-M8U-04B-00 FLASH FW 3.01 UDR 1.21 N/A Mass production
NEO-M8U NEO-M8U-05B-00 FLASH FW 3.01 UDR 1.31 UBX-20014805 Initial production
NEO-M8U NEO-M8U-06B-00 FLASH FW 3.01 UDR 1.50 UBX-20053641 Initial production
N/A Mass production
Product status
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-blox AG.
ined herein is provided “as is” and u-blox assumes no liability for its use. No warranty, either express or
to, with respect to the accuracy, correctness, reliability and fitness for a particular
information. This document may be revised by u-blox at any time without notice. For the most recent
-blox.com.
-blox.
NEO-M8U - Hardware integration manual
Contents
Document information ................................................................................................................................ 2
Contents .......................................................................................................................................................... 3
1 Hardware description ........................................................................................................................... 5
1.1 Overview ........................................................................................................................................................ 5
1.2 Configuration ............................................................................................................................................... 5
1.3 Connecting power ....................................................................................................................................... 5
1.3.1 VCC: Main supply voltage ................................................................................................................. 5
1.3.2 V_BCKP: Backup supply voltage ...................................................................................................... 5
1.3.3 VDD_USB: USB interface power supply ......................................................................................... 6
1.3.4 VCC_RF: Output voltage RF ............................................................................................................. 6
1.4 Interfaces ...................................................................................................................................................... 6
1.4.1 UART ..................................................................................................................................................... 6
1.4.2 USB ........................................................................................................................................................ 6
1.4.3 Display Data Channel (DDC) ............................................................................................................. 7
1.4.4 SPI .......................................................................................................................................................... 7
1.4.5 TX Ready signal ................................................................................................................................... 8
1.5 I/O pins ........................................................................................................................................................... 8
1.5.1 Electromagnetic interference on I/O lines ..................................................................................... 8
2 Design ..................................................................................................................................................... 10
2.1 Pin description ...........................................................................................................................................10
2.1.1 Pin name changes.............................................................................................................................11
2.2 Minimal design...........................................................................................................................................11
2.3 Layout: Footprint and paste mask ........................................................................................................11
2.4 Antenna .......................................................................................................................................................12
2.4.1 Antenna design with passive antenna .........................................................................................12
2.4.2 Active antenna design .....................................................................................................................13
3 Untethered dead reckoning............................................................................................................. 15
3.1 Implementation .........................................................................................................................................15
3.2 Installation ..................................................................................................................................................15
3.3 Initialization and calibration ...................................................................................................................15
4 Migration from NEO-M8L to NEO-M8U ...................................................................................... 16
4.1 Hardware migration NEO-M8L to NEO-M8U ......................................................................................16
5 Product handling ................................................................................................................................. 17
5.1 Packaging, shipping, storage and moisture preconditioning ..........................................................17
5.2 Soldering .....................................................................................................................................................17
5.3 EOS/ESD/EMI precautions ......................................................................................................................20
5.4 Applications with cellular modules ........................................................................................................23
Appendix ....................................................................................................................................................... 25
A.1 Recommended parts ................................................................................................................................25
A.2 Recommended antennas ........................................................................................................................26
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Related documents ................................................................................................................................... 27
Revision history .......................................................................................................................................... 27
Contact .......................................................................................................................................................... 28
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1 Hardware description
1.1 Overview
The NEO-M8U is an untethered dead reckoning (UDR) module bringing the benefits of dead reckoning
to a wider range of road-vehicle applications by eliminating the need for a speed or wheel-tick
connection to the vehicle. The module uses built-in gyroscope and accelerometer sensors and
features the high-performance u-blox M8 concurrent positioning engine. Available in the NEO
industry standard leadless chip carrier (LCC) package, it is easy to integrate and combines
exceptional positioning performance with highly flexible power, design, and connectivity options. SMT
pads allow fully automated assembly with standard pick & place and reflow-soldering equipment for
cost-efficient, high-volume production enabling short time-to-market.
☞ For more about product features see the NEO-M8U Data sheet [1].
☞ To determine which u-blox product best meets your needs, see the product selector tables on the
u-blox website www.u-blox.com.
1.2 Configuration
The configuration settings can be modified using UBX protocol configuration messages (see u-blox 8
/ u-blox M8 Receiver Description Including Protocol Specification [2]). The modified settings remain
effective until power-down or reset. If these settings have been stored in BBR (battery-backed RAM),
then the modified configuration will be retained, as long as there is no backup battery supply interrupt.
For NEO-M8U modules, the configuration can be saved permanently in SQI flash.
1.3 Connecting power
The NEO-M8U positioning module has up to three power supply pins: VCC, V_BCKP and VDD_USB.
1.3.1 VCC: Main supply voltage
The VCC pin provides the main supply voltage. During operation, the current drawn by the module can
vary by some orders of magnitude. For this reason, it is important that the supply circuitry be able to
support the peak power for a short time (see the NEO-M8U Data sheet [1] for specification).
☞ When switching from backup mode to normal operation or at start-up, the NEO-M8U module must
charge the internal capacitors in the core domain. In certain situations, this can result in a
significant current draw. It is important that the power supply or low ESR capacitors at the module
input can deliver this current/charge.
☞ Use a proper GND concept. Do not use any resistors or coils in the power line.
1.3.2 V_BCKP: Backup supply voltage
If the module supply has a power failure, the V_BCKP pin supplies the real-time clock (RTC) and
battery-backed RAM (BBR). Use of valid time and the GNSS orbit data at startup will improve the
GNSS performance, as with hot starts, warm starts, AssistNow Autonomous and AssistNow Offline.
If no backup battery is connected, the module performs a cold start at power up.
☞ A backup supply voltage should be provided to the NEO-M8U to enable navigation by dead
reckoning before the first GNSS fix.
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☞ Avoid high resistance on the V_BCKP line: During the switch from main supply to backup supply,
a short current adjustment peak can cause high voltage drop on the pin with possible
malfunctions.
☞ If no backup supply voltage is available, connect the V_BCKP pin to VCC.
☞ As long as power is supplied to the NEO-M8U module through the VCC pin, the backup battery is
disconnected from the RTC and the BBR to avoid unnecessary battery drain (see Figure 1). In this
case, VCC supplies power to the RTC and BBR.
Figure 1: Backup battery and voltage (for exact pin orientation, see the NEO-M8U Data sheet [1])
1.3.3 VDD_USB: USB interface power supply
VDD_USB supplies the USB interface. If the USB interface is not used, the VDD_USB pin must be
connected to GND. For more information about correctly handling the VDD_USB pin, see section 1.4.
1.3.4 VCC_RF: Output voltage RF
The VCC_RF pin can supply an active antenna or external LNA. For more information, see section 2.4.
1.4 Interfaces
1.4.1 UART
NEO-M8U 3D dead reckoning module includes a Universal Asynchronous Receiver Transmitter
(UART) serial interface RXD/TXD supporting configurable baud rates. The baud rates supported are
specified in the NEO-M8U Data Sheet [1].
The signal output and input levels are 0 V to VCC. An interface based on RS232 standard levels (+/12 V) can be implemented using level shifters such as Maxim MAX3232. Hardware handshake signals
and synchronous operation are not supported.
1.4.2 USB
A USB version 2.0 FS (full speed, 12 Mb/s) compatible interface is available for communication as an
alternative to the UART. The USB_DP integrates a pull-up resistor to signal a full-speed device to the
host. The VDD_USB pin supplies the USB interface.
u-blox provides Microsoft® certified USB drivers for Windows Vista, Windows 7, Windows 8 and
Windows 10. These drivers are available at our website at www.u-blox.com.
USB external components
The USB interface requires some external components to implement the physical characteristics
required by the USB 2.0 specification. These external components are shown in Figure 2 and listed in
Table 1. To comply with USB specifications, VBUS must be connected through an LDO (U1) to pin
VDD_USB on the module.
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Module
VDD
_USB
LDO
VDD
_USB
R4
USB_DP
USB
_DM
R5
C24 C23
D2
VBUS
DP
DM
GND
USB Device Connector
U1
EN R11
EN
In USB self-powered mode, the power supply (VCC) can be turned off and the digital block is not
powered. In this case, since VBUS is still available, the USB host would still receive the signal indicating
that the device is present and ready to communicate. This should be avoided by disabling the LDO
(U1) using the enable signal (EN) of the VCC-LDO or the output of a voltage supervisor. Depending on
the characteristics of the LDO (U1), it is recommended to add a pull-down resistor (R11) at its output
to ensure VDD_USB is not floating if the LDO (U1) is disabled or the USB cable is not connected, that
is, VBUS is not supplied.
☞ USB bus-powered mode is not supported.
Figure 2: USB interface
Name Component Function Comments
U1 LDO
C23, C24 Capacitors Required according to the specification of LDO U1
D2
R4, R5
R11 Resistor
Table 1: Summary of USB external components
Protection
diodes
Serial
termination
resistors
Regulates VBUS (4.4 …5.25 V)
down to a voltage of 3.3 V.
Protect circuit from overvoltage /
ESD when connecting.
Establish a full-speed driver
impedance of 28…44 Ω
Almost no current requirement (~1 mA) if the GNSS receiver is
operated as a USB self-powered device.
Use low capacitance ESD protection such as ST Microelectronics
USBLC6-2.
A value of 27 Ω is recommended.
100 kΩ is recommended for USB self-powered setup.
1.4.3 Display Data Channel (DDC)
An I2C-compatible Display Data Channel (DDC) interface is available with a NEO-M8U module for
serial communication with an external host CPU. The interface only supports operation in slave mode
(master mode is not supported). The DDC protocol and electrical interface are fully compatible with
the fast-mode of the I2C industry standard. DDC pins SDA and SCL have internal pull-up resistors.
For more information about the DDC implementation, see the u-blox 8 / u-blox M8 Receiver
Description Including Protocol Specification [2]. For bandwidth information, see the NEO-M8U Data
sheet [1]. For timing, parameters consult the I2C-bus specification [5].
☞ The NEO-M8U DDC interface supports serial communication with u-blox cellular modules. See the
specification of the applicable cellular module to confirm compatibility.
1.4.4 SPI
An SPI interface is available for communication to a host CPU.
☞ SPI is not available in the default configuration because its pins are shared with the UART and DDC
interfaces. The SPI interface can be enabled by connecting D_SEL to ground. For speed and clock
frequency, see the NEO-M8U Data sheet [1].
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1.4.5 TX Ready signal
The TX Ready signal indicates that the receiver has data to transmit. A listener can wait on the TX
Ready signal instead of polling the DDC or SPI interfaces. The UBX-CFG-PRT message lets you
configure the polarity and the number of bytes in the buffer before the TX Ready signal goes active.
The TX Ready signal can be mapped to UART TXD (PIO 06). The TX Ready function is disabled by
default.
☞ The TX Ready functionality can be enabled and configured by AT commands sent to the u-blox
cellular module supporting the feature. For more information, see GPS Implementation and Aiding
Features in u-blox wireless modules [6].
1.5 I/O pins
RESET_N: Reset input
Driving RESET_N low activates a hardware reset of the system. Use this pin to reset the module only.
Do not use RESET_N to turn the module on and off, since the reset state increases power
consumption, or as a POR. With the NEO-M8U module the RESET_N pin is an input only.
☞ RESET_N should be used only 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.
D_SEL: Interface select
The D_SEL pin selects the available interfaces. SPI cannot be used simultaneously with the
UART/DDC. If open, UART and DDC are available. If pulled low, the SPI interface is available. For more
information see the NEO-M8U Data sheet [1].
LNA_EN: LNA enable
In power save mode, the system can turn on/off an optional external LNA using the LNA_EN signal in
order to optimize power consumption.
TIMEPULSE
A configurable time pulse signal is available with the NEO-M8U module. It generates pulse trains
synchronized with GPS or UTC time grid with intervals configurable over a wide frequency range. The
time pulse signal is disabled by default. For more information, see the u-blox 8 / u-blox M8 Receiver
Description Including Protocol Specification [2].
☞ The NEO-M8U time pulse output is configured using messages for “TIMEPULSE2”.
☞ The time pulse output must not be held LOW during start-up.
1.5.1 Electromagnetic interference on I/O lines
Any I/O signal line with a length greater than approximately 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, in which 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 15).
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To avoid interference by improperly shielded lines, it is recommended to use resistors (for example,
R>20 Ω), ferrite beads (for example, BLM15HD102SN1) or inductors (for example, LQG15HS47NJ02)
on the I/O lines in series. Choose these components carefully because they also affect the signal rise
times.
Figure 3 shows an example of EMI protection measures on the RX/TX line using a ferrite bead. More
information can be found in section 5.3.
Figure 3: EMI precautions design
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