u-blox NEO-M8L User Manual
performance
blox M8
www.u-blox.com
NEO-M8L
u-blox M8 automotive dead reckoning modules
including 3D sensors
Hardware integration manual
Abstract
This document describes the features and specifications of NEO-M8L, a highautomotive dead reckoning (ADR) module with 3D sensors. The module includes the uconcurrent GNSS engine with reception of GPS, GLONASS, BeiDou, Galileo and QZSS signals.
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NEO-M8L
u-blox M8 automotive dead reckoning modules including 3D sensors
Hardware integration manual
UBX-16010549
R09 12-Feb-2021
Early Production Information
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.
This document applies to the following products:
Product name Type number ROM/FLASH version PCN/IN reference
NEO-M8L NEO-M8L-0-12 Flash FW3.01 ADR 4.11 UBX-17049965
NEO-M8L-04B NEO-M8L-04B-00 Flash FW3.01 ADR 4.21 N/A
NEO-M8L-05B NEO-M8L-05B-00 Flash FW3.01 ADR 4.31 UBX-20014805
NEO-M8L-06B NEO-M8L-06B-00 Flash FW3.01 ADR 4.50 UBX-20053641
h the express written permission of u-blox.
-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
-blox at any time without notice. For the most recent
-blox.com.
-blox AG.
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Early Production Information
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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 RESET_N: Reset input ....................................................................................................................... 8
1.5.2 WHEELTICK: Wheel tick input ......................................................................................................... 8
1.5.3 FWD: Forward/reverse input ............................................................................................................ 8
1.5.4 D_SEL: Interface select ..................................................................................................................... 9
1.5.5 LNA_EN: LNA enable .......................................................................................................................... 9
1.5.6 TIMEPULSE.......................................................................................................................................... 9
1.6 Electromagnetic interference on I/O lines ............................................................................................. 9
2 Design ..................................................................................................................................................... 10
2.1 Pin description ...........................................................................................................................................10
2.1.1 Pin name changes.............................................................................................................................10
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 Automotive dead reckoning ............................................................................................................ 14
3.1 Implementation .........................................................................................................................................14
3.2 Sensor calibration .....................................................................................................................................14
3.3 Software migration ...................................................................................................................................14
4 Product handling ................................................................................................................................. 15
4.1 Packaging, shipping, storage and moisture preconditioning ..........................................................15
4.2 Soldering .....................................................................................................................................................15
4.3 EOS/ESD/EMI precautions ......................................................................................................................19
4.4 Safety precautions ...................................................................................................................................21
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4.5 Applications with cellular modules ........................................................................................................22
Appendix ....................................................................................................................................................... 24
A Recommended parts ......................................................................................................................... 24
B Recommended antennas ................................................................................................................. 25
Related documents ................................................................................................................................... 26
Revision history .......................................................................................................................................... 27
Contact .......................................................................................................................................................... 28
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1 Hardware description
1.1 Overview
The NEO-M8L modules are 3D dead reckoning GNSS receivers for automotive applications using a
built-in 6-axis sensor (3-axis gyroscope and 3-axis accelerometer) and featuring the highperformance u-blox M8 concurrent positioning engine. Available in the NEO industry standard
leadless chip carrier (LCC) package, they are easy to integrate and they combine 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 costefficient, high-volume production enabling short time-to-market.
☞ For more information about the product features, see the corresponding product data sheet [1],
or [2] in the Related documents section.
☞ 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 the ublox 8 / u-blox M8 Receiver Description Including Protocol Specification
remain effective until power-down or reset. If these settings have been stored in battery-backed RAM
(BBR), then the modified configuration will be retained, as long as the backup battery supply is not
interrupted.
[3]). The modified settings
For NEO-M8L modules, the configuration can be saved permanently in SQI flash.
1.3 Connecting power
The NEO-M8L positioning modules have 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, especially if enabling low-power operation modes. For this reason,
it is important that the supply circuitry be able to support the peak power for a short time (see the
corresponding product data sheet in the Related documents section for the specifications).
☞ When switching from backup mode to normal operation or at start-up, the NEO-M8L modules
must charge the internal capacitors in the core domain. In certain situations, this can result in a
significant current draw. For low power applications using power save and backup modes, 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-M8L 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-M8L modules 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 corresponding product data sheet)
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
For more information about the interfaces (baud rates, bandwidth, speed and clock frequency, and so
on), see the corresponding product data sheet [1], or [2] in the Related documents section.
1.4.1 UART
NEO-M8L 3D dead reckoning modules include a Universal Asynchronous Receiver Transmitter
(UART) serial interface RXD/TXD supporting configurable baud rates.
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, 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
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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
Almost no current requirement (~1 mA) if the GNSS receiver is
Table 1. To comply with USB specifications, VBUS must be connected through an LDO (U1) to pin
VDD_USB on the module.
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
D2 Protection diodes
R4, R5
R11 Resistor
Table 1: Summary of USB external components
Capacitors Required according to the specification of LDO U1.
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
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-M8L 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 [3]. For timing, parameters consult the I2C-bus
specification [8].
☞ The NEO-M8L 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.
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☞ 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 corresponding product data sheet in the Related documents section.
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 the GPS Implementation and
Aiding Features in u-blox wireless modules
[9].
1.5 I/O pins
1.5.1 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. With the NEO-M8L modules the RESET_N pin is an input only.
☞ Use RESET_N in critical situations only to recover the system. RESET_N also resets the real-time
clock which means that the receiver cannot perform hot start immediately after RESET_N.
1.5.2 WHEELTICK: Wheel tick input
The wheel tick input, also known as the HW interface, is used to provide speed pulse (wheel tick)
information to the NEO-M8L modules. By default the wheel tick count is based on the rising edge of
the wheel tick pulse signal. To improve performance with lower rate mechanically derived wheel-tick
signals, the receiver may be configured to use both the rising and falling edges of the wheel tick signal
on the condition that the wheel tick pulses have approximately 1:1 mark:space ratio regardless of
speed. The minimum recommended pulse width is 10 us.
The pulse interval (WT resolution) should be less than 40 cm per tick over distance travelled. For best
performance, less than 2 cm/tick is recommended. The wheel tick pulse output shall change linearly
with the change in speed (navigation filter estimates only the linear scale factor). If the vehicle is
standing still, there should be no wheel tick pulses. This is particularly important at system shut down
and power up. If there is a dead-band (wheel tick pulse does not change or is not output below a certain
speed), performance will be affected at low speed.
If the speed pulse is available from the host processor, then the information can also be provided by
SW interface using the UBX-ESF-MEAS message. In this particular case, the wheel-tick pin can be
configured as EXTINT1 and used to provide a time mark for the message. For more information, see
the u-blox 8 / u-blox M8 Receiver Description Including Protocol Specification [3].
☞ Do not exceed the maximum voltage of 3.6 V at the input when using the HW interface.
1.5.3 FWD: Forward/reverse input
The forward/reverse input is used to indicate the moving direction by an external signal (HW
interface). By default the wheel-tick direction pin polarity is automatically initialized once the vehicle
has reached required minimum speed of 30 km/h. The forward/reverse input polarity can also be set
manually. If the forward/reverse information is available from the host processor, the UBX-ESF-MEAS
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TX
RX
GNSS
Receiver
FB
FB
BLM 15HD102SN1
>10mm
message can also be used to provide the direction of motion (SW interface). For more information,
see the u-blox 8 / u-blox M8 Receiver Description Including Protocol Specification [3].
☞ Do not exceed the maximum voltage of 3.6 V at the input when using the HW interface. When
using a SW interface this pin is not used and can be left open.
☞ No forward or reverse input will cause incorrect operation.
1.5.4 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.
1.5.5 LNA_EN: LNA enable
In power save mode, the system can turn on/off an optional external LNA using the LNA_EN signal to
optimize power consumption.
1.5.6 TIMEPULSE
A configurable time pulse signal is available with the NEO-M8L modules. It generates pulse trains
synchronized with GPS or UTC time grid with intervals configurable over a wide frequency range. For
more information, see the u-blox 8 / u-blox M8 Receiver Description Including Protocol Specification
[3].
☞ The NEO-M8L time-pulse output is configured using messages for “TIMEPULSE2”.
☞ The time pulse output must not be held LOW during start-up.
1.6 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 16).
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.
Figure 3: EMI precautions
More information is available in section 4.3.
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