Ublox EVK-M8T-0-01 User manual

EVK-M8T
Evaluation Kit
User Guide

Abstract
This document describes the structure and use of the EVK-
M8T evaluation kit and provides
information for evaluating and testing u-
blox M8 positioning technology for timing and raw data
applications.
www.u-blox.com
UBX-14041540 - R05

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Document Information
Title EVK-M8T
Subtitle User Guide
Document type User Guide
Document number UBX-14041540
Revision and date R05 20-May-2018
Document status Early Production Information
This document applies to the following products:
Product name Type number Hardware version ROM/FLASH version PCN reference
EVK-M8T EVK-M8T-0-01 B Flash FW 3.01 TIM 1.10 UBX-16005636
European Union regulatory compliance
EVK-M8T complies with all relevant requirements for RED 2014/53/EU. The EVK-M8T Declaration of Conformity (DoC) is
available at www.u-blox.com under Support --> Product Resources --> Conformity Declaration.
u-blox or third parties may hold intellectual property rights in the products, names, logos and designs included in this
document. Copying, reproduction, modification or disclosure to
third parties of this document or any part thereof is only
permitted with the express written permission of u
-blox.
The information contained herein is provided “as is” and u
-blox assumes no liability for its use. No warranty, either express or
implied, is
given, including but not limited to, with respect to the accuracy, correctness, reliability and fitness for a particular
purpose of the information. This document may be revised by u
-blox at any time without notice. For the most recent
documents, visit ww
w.u-blox.com.
Copyright © u
-blox AG.

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Contents
Document Information................................................................................................................................2
Contents ..........................................................................................................................................................3
1Product description ..............................................................................................................................4
1.1 Overview........................................................................................................................................................ 4
1.2 Kit includes ................................................................................................................................................... 4
1.3 Software and documentation................................................................................................................... 4
1.3.1 u-center GNSS evaluation software ............................................................................................... 4
1.4 System requirements ................................................................................................................................ 4
2Specifications ......................................................................................................................................... 5
2.1 Safety precautions ..................................................................................................................................... 5
3Getting Started......................................................................................................................................6
3.1 Software installation.................................................................................................................................. 6
3.2 Hardware installation................................................................................................................................. 6
3.3 Serial port default configuration ............................................................................................................. 6
4Device description................................................................................................................................. 7
4.1 Interface connection and measurement................................................................................................ 7
4.2 Active antenna............................................................................................................................................. 7
4.3 Evaluation unit............................................................................................................................................. 7
4.3.1 Antenna connector............................................................................................................................. 7
4.3.2 USB ........................................................................................................................................................ 7
4.3.3 UART ..................................................................................................................................................... 8
4.3.4 RST button...........................................................................................................................................8
4.3.5 Safe boot button.................................................................................................................................8
4.3.6 Slide Switch..........................................................................................................................................8
4.3.7 Test Connector.................................................................................................................................... 9
4.3.8 LED....................................................................................................................................................... 10
4.3.9 Backup Battery.................................................................................................................................. 10
4.3.10 GNSS Configuration......................................................................................................................... 10
5Measuring tracking current .............................................................................................................. 11
6Testing Power Save Mode ................................................................................................................ 12
7Block diagram ....................................................................................................................................... 13
8Board layout........................................................................................................................................... 14
9Schematic .............................................................................................................................................. 17
10 Battery replacement .......................................................................................................................... 18
11 Troubleshooting................................................................................................................................... 19
12 Common evaluation pitfalls ............................................................................................................. 21
Related documents ....................................................................................................................................22
Revision history...........................................................................................................................................22
Contact.......................................................................................................................................................... 23

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1Product description
1.1 Overview
EVK-M8T evaluation kit makes evaluating the high performance u-blox M8T positioning products
simple. The built-in USB interface provides both power supply and high-speed data transfer, and
eliminates the need for an external power supply. The u-blox evaluation kits are compact, and their
user friendly interface and power supply make them ideally suited for use in laboratories, vehicles
and outdoor locations. Furthermore, they can be used with a PDA or a notebook PC, making them the
perfect companion through all stages of design-in projects.
Evaluation Kit Description Suitable for
EVK-M8T u-blox M8 Timing GNSS Evaluation Kit NEO-M8T, LEA-M8T
Table 1: List of products supported by EVK-M8T evaluation kit
1.2 Kit includes
•Evaluation unit
•USB cable
•Active GPS / GLONASS / BeiDou antenna with 3 m cable
•Quick Start card
1.3 Software and documentation
The EVK installation software (and documentation) package can be downloaded from the Web; see
the Quick Start card for the URL.
1.3.1 u-center GNSS evaluation software
The installation software includes u-center, an interactive tool for configuration, testing,
visualization and data analysis of GNSS receivers. It provides useful assistance during all phases of
a system integration project.
1.4 System requirements
•PC with USB interface
•Operating system: Windows Vista onwards (x86 and x64 versions)
•USB drivers are provided in the evaluation kit installation software

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2Specifications
Parameter Specification
Serial Interfaces 1 USB V2.0
1 RS232, max. baud rate 921,6 kBd
DB9 +/- 12 V level
14 pin – 3.3 V logic
1 DDC (I2C compatible) max. 400 kHz
1 SPI – clock signal max. 5,5 MHz – SPI DATA max. 1 Mbit/s
Timing Interfaces 2 Time-pulse outputs
1 Time-mark input
Dimensions 105 x 64 x 26 mm
Power Supply 5V via USB or external powered via extra power supply
pin 14 (V5_IN) 13 (GND)
Normal Operating temperature -40°C to +65°C
Table 2: EVK-M8T specifications
2.1 Safety precautions
EVK-M8T must be supplied by an external limited power source in compliance with clause 2.5 of the
standard IEC 60950-1. In addition to an external limited power source, only separated or Safety Extra-
Low Voltage (SELV) circuits are to be connected to the evaluation kit, including interfaces and
antennas.
For more information about SELV circuits see section 2.2 in Safety standard IEC 60950-1 .
Warnings and certifications
CAUTION! IN THE UNLIKELY EVENT OF A FAILURE IN THE INTERNAL
PROTECTION CIRCUITRY THERE IS A RISK OF AN EXPLOSION WHEN CHARGING
FULLY OR PARTIALLY DISCHARGED BATTERIES. REPLACE THE BATTERY IF IT
NO LONGER HAS SUFFICIENT CHARGE FOR UNIT OPERATION. CONTROL THE
BATTERY BEFORE USING IF THE DEVICE HAS NOT BEEN OPERATED FOR AN
EXTENDED PERIOD OF TIME.
Products marked with this lead-free symbol on the product label comply with the
“
Directive 2002/95/EC of the European Parliament and the Council on the
Restriction of Use of certain Hazardous Substances in Electrical and Electronic
Equipment” (RoHS).
EVK-M8T evaluation kit is RoHS compliant and green (no halogens).

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3Getting Started
3.1 Software installation
☞Installation of the EVK-M8T software and documentation requires Internet access.
Choose Software only or Software and documentation installation package from u-blox website.
Once the zip file is downloaded and unzipped, unzip the file in Tools folder and double-click the
extracted exe file.
The software components will be installed on your system and placed under the “u-blox” folder in the
“Start Programs” menu.
3.2 Hardware installation
1. Connect the unit to a PC running Microsoft Windows. Options:
•USB: Connect via USB port.
•UART: Connect via RS232. Set slide switch to I2C.
•SPI / I2C compliant DDC: Connect corresponding pins (see Table 5 for pin description). Set slide
switch accordingly to SPI or I2C.
☞Press the RST button after changing the switch.
2. The device must always have power, either via USB on the back or the V5_IN input on the front.
3. Connect the GNSS antenna to the evaluation unit and place the antenna in a location with good
sky view.
4. Start the u-center GNSS Evaluation Software and select corresponding COM port and baud rate.
☞Refer to the u-center User Guide [5] for more information.
3.3 Serial port default configuration
Parameter Description Remark
UART Port 1, Input UBX and NMEA protocol at 9’600 Bd
UART Port 1, Output UBX and NMEA protocol at 9’600 Bd Only NMEA messages are activated
USB, Input UBX and NMEA protocol
USB, Output UBX and NMEA protocol Only NMEA messages are activated
Table 3: Default configuration

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4Device description
4.1 Interface connection and measurement
For connecting the EVK to a PC, use a standard SUBD-9 cable and the included Micro-USB cable.
Additional measurement equipment can be connected to the front connector.
Figure 1: Connecting the unit for power supply and communication
4.2 Active antenna
EVK-M8 evaluation kits include a GPS / GLONASS / BeiDou antenna with a 3 m cable. It is possible to
connect various active and passive GNSS antennas with SMA connectors to the evaluation unit.
The recommended maximum antenna supply current for active antennas is 30 mA.
4.3 Evaluation unit
Figure 2 shows the front and the rear panel of the EVK-M8T evaluation unit.
Front panel Rear panel
Figure 2: EVK-M8T evaluation unit – front and rear panels
4.3.1 Antenna connector
An SMA female jack is available on the front side (see Figure 2) of the evaluation unit for connecting
an active or passive antenna. DC voltage at the RF input is 3.3 V. The internal short circuit protection
limits the maximum current to 60 mA. Please note that the 30 mA maximum supply current for
active antenna stays the same. This pin is also ESD protected.
The u-blox NEO-M8T module used in the EVK-M8T incorporates an additional, off-chip LNA.
⚠The connector is only to be used with a GNSS antenna or simulator. Do not connect this
equipment to cable distribution systems.
4.3.2 USB
A USB V2.0 compatible serial port is featured for data communication and power supply.

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4.3.3 UART
The evaluation unit includes an RS232 port for serial communication that is compatible with PC
serial ports.
Connect using a straight RS232 serial cable with male and female connectors to the port on your
PC. The maximum cable length is < 3.0 meters. To configure the RS232 port, use the CFG-PRT
command in the u-center application. The maximum operating baud rate is 921.6 kBd.
If you are using a USB to RS232 adaptor cable, you can connect it directly to the evaluation kit RS232
port.
The 9-pin D-SUB female connector is assigned as listed in Table 4:
Pin Nr. Assignment
1 Time-pulse 1 output (RS-232 levels)
2 TXD, GNSS Transmit Data, serial data to DTE
3 RXD, GNSS Receive Data, serial data from DTE
4 Optional time-mark input (RS-232 levels) using EXTINT0 (internal jumper J6 fitment required)
5 GND
6 Time-pulse 1 output (RS-232 levels)
7 Not connected
8, 9 not connected
Table 4: SUB-D9 Connector pin description for EVK-M8T
4.3.4 RST button
The RST button on the front panel resets the unit. To avoid an inadvertent reset, the button is
recessed.
4.3.5 Safe boot button
This is used to set the unit in safe boot mode. In this mode the receiver executes only the minimal
functionality, such as updating new firmware into the SQI flash. In order to set the receiver in safe
boot mode please follow these steps.
1. Press the BOOT button and keep holding
2. Press the RST button
3. Release the RST button
4. Release the BOOT button
5. If the UART interface has to be used, the training sequence has to be sent to the receiver.
The training sequence is a transmission of 0x55 55 at the baud rate of 9600 Bd. Wait for at least
100 milliseconds before the interface is ready to accept commands.
4.3.6 Slide Switch
Use the slide switch on the front panel to choose between I2C (and UART) and SPI communication
ports. You must reset the unit by pressing the RST button when the slide switch has been changed.
1.
I2C – In this selection the EVK operates with the UART (RS232 DB9 – rear panel or the 3.3 V level
TxD (MISO), RxD (MOSI) at the front panel). Also the communication via 3.3 V DDC interface (I2C)
is selected.
2.
SPI – In this selection the EVK operates only with the SPI interface. RS232 (DB9) is switched off.

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4.3.7 Test Connector
This 14-pin test-connector provides additional functionality to the EVK, allowing access to the
interface pins and an ability to measure the current used by the EVK. All pins are ESD protected.
For accurate measurements, it is recommended to use a cable of at most 1 meter in length. Figure 3
shows an example of a power supply connected to the test connector by using standard adapter
cables from the manufacture Hirschmann. Figure 4 shows an example for overall current
measurement. When connecting the 3.3 V digital interfaces RS232, SPI and DDC to your application,
a cable length less than 25 cm is recommended.
PIN Nr. PIN NAME I/O LEVEL DESCRIPTION
14 V5_IN I 4.75 V - 5.25 V Power input – can be used instead of USB
13 GND I - Common ground pin
12 P1A (VCC) O 3.3 V Power output – max. current supply 100 mA
1Ω1% resistor for over-all current measurement to pin 11 (P1B)
NOTE: the current includes also SQI Flash, LNA
11 P1B O Second connection for over-all current measurement (see Figure 5)
10 P2A O 3.0 V Battery output (unloaded)
100 Ω1% resistor for battery backup current measurement to pin 9 (P2B)
NOTE: There is a current protection to 3 mA. See circuit in figure 7 (D2, D4,
R29)
9 P2B O Second junction for battery backup current measurement
8 TIMEPULSE 1 O 3.3V Time pulse 1 (internally buffered output)
7 EXTINT0 I 3.3 V External interrupt or time-mark input
6 TIMEPULSE 2 O 3.3 V Time pulse 2 (internally buffered output)
5 SDA / CS I/O 3.3 V If slide switch on I2C, then DDC interface selected; Function: data input /
output
If slide switch on SPI, then SPI interface selected; chip select input – LOW
ACTIVE
4 SCL / SCK I/O 3.3 V Clock input / output
3 TxD / MISO I/O 3.3 V If slide switch on I2C, then DDC interface selected / UART TxD (3.3V Level)
If slide switch on SPI, then SPI interface selected; Master in Slave out (MISO)
2 RxD / MOSI I/O 3.3 V If slide switch on I2C, then DDC interface selected / UART RxD (3.3V Level)
If slide switch on SPI, then SPI interface selected; Master out Slave in (MOSI)
1 GND I - Common ground pin
Table 5: Connector pin description for EVK-M8T (pins numbered from right to left on the front panel)
V5_IN
GND
GND
V5_IN
Hirschmann
Part Nr.: 934160100
Figure
3: Example 5V DC power supply

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4.3.8 LED
On the front panel of the unit, a single blue LED shows the time pulse 1 signal. The LED starts flashing
one pulse per second during a GNSS fix. If there is no GNSS fit, the LED will only light, without
flashing.
4.3.9 Backup Battery
There is a backup battery in the evaluation unit. This is necessary to store orbital information
between operations and to enable faster start-up. It is a RENATA 3.0 V Li / MnO²battery of the type
CR2450. The battery has a rated capacity of 540 mA. The battery operating temperature range is -
40° C to +85° C.
If the built-in backup battery runs low or is empty after a long storage period, purchase the battery
described above for replacement (refer to the section 10 for battery replacement guidelines).
⚠CAUTION! RISK OF EXPLOSION IF BATTERY IS REPLACED BY AN INCORRECT TYPE. DISPOSE
OF USED BATTERIES ACCORDING TO THE INSTRUCTIONS!
4.3.10 GNSS Configuration
The EVK-M8T supports GPS, QZSS, Galileo, GLONASS, and BeiDou.
The GNSS to be used can be configured on u-center (View Messages View then UBX-CFG-GNSS).
For more information, refer to the
u-center User Guide [5], the u-blox 8 / u-blox M8 Receiver
Description including Protocol Specification
[4].

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5Measuring tracking current
To measure the tracking current with EVK-M8T, follow these steps:
1. Connect a true RMS voltmeter across P1A (VCC) and P1B of the front connector. (See Figure 4.)
2. Wait 12 minutes to download all GNSS orbital data, or download all the Aiding Data via the
AssistNow Online service.
3. Read the voltage (and average if necessary) on the voltmeter and convert to current (1 mV equals
1 mA).
4. Perform the test with good signals and clear sky view to ensure that the receiver can acquire the
satellite signals.
☞The overall current measurement also includes the internal SQI flash. For ROM based products
the current will be lower.
For more details see the circuit in Figure 7.
Hirschmann
Part Nr.: 934160100
P1A (VCC)
P1B
P1B
P1A
(VCC)
Figure
4: Example – tracking current measurement

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6Testing Power Save Mode
When testing Power Save Mode with EVK-M8, observe the following points:
•When configuring Power Save Mode you must set up the parameters using the CFG-PM2
message first and then enable Power Save Mode using CFG-RXM. The Configuration view or
Messages view of the u-center evaluation software can be used to do this. When enabling the
mode using CFG-RXM, always save the configuration by checking the “save configuration” box in
u-center, otherwise the configuration will be lost.
•Communications to the evaluation kit must be via the UART, I2C or SPI (not USB).
•The evaluation kit can be supplied via the USB connector or via V5_IN at the front panel
connector. Do not connect the USB cable to the PC! This can be done by either connecting a USB
cable from the evaluation kit to a USB hub, or by using a USB power connector.
•When altering the Power Save Mode configuration, first disable the mode using CFG-RXM
(remember to enable “save configuration” again), before changing the CFG-PM2 parameters.
Then re-enable Power Save Mode.
☞For more information, refer to the u-blox 8 / u-blox M8 Receiver Description including Protocol
Specification [4].

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7Block diagram
Figure
5: EVK-M8T block diagram

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8Board layout
Figure 6 shows the EVK-M8T board layout (PCB Version B). See Table 6 for the component list of the
EVB.
Figure
6: EVB-M8T layout

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PART DESCRIPTION
A1 GPS RECEIVER U-BLOX NEO-M8T-0-00 -40/+85C
BT1 BATTERY HOLDER RENATA CR2450N 3V
C1 C11 C13 C22 CAP CER X5R 0603 1U0 10% 6.3V
C2 C4 C6 C7 C8 C10 C14 C16 C19 CAP CER X7R 0603 100N 10% 10V
C3 C25 CAP CER X5R 1210 10U 10% 10V
C5 CAP CER X7R 0402 1N0 10% 16V
C9 C12 CAP CER X7R 0603 10N 10% 25V
C21 CAP CER COG 0402 22P 5% 25V
C24 CAP CER X5R 0402 100N 10% 10V
D1 D2 D4 D5 SURFACE MOUNT SCHOTTKY BARRIER RECTIFIER SS14 1A -55/+125C
D3 R17 R18 R20 R21 R22 R23 ESD PROTECTION FOR HIGH SPEED LINES, TYCO, 0.25PF, PESD0402-140 -55/+125C
DS1 LED OSRAM HYPER MINI TOPLED LB M673-L1N2-35 BLUE 0.02A
FB1 FERRITE BEAD MURATA BLM15HD 0402 1000R@100MHZ
J1 CON USB RECEPTACLE MICRO B TYPE SMD – MOLEX 47346-0001 – TID60001597
30V 1A
J2 CON SMA SMD STRAIGHT JACK 11.4MM HEIGHT WITHOUT WASHER AND NUT
J3 9 POLE SUBD CONNECTOR FEMALE
J4 14PIN 90\xB0 2.54MM PITCH DISCONNECTABLE CRIMP CONNECTOR -40/+85C
J6 CON 1-ROW THT 100MIL GRID 2PINS 0.64MM SQUARE 6.1MM HEIGHT
L2 IND MURATA LQW15A 0402 120N 5% 0.64A -55/+125C
Q1 MBT3906DW1T1G DUAL GENERAL PURPOSE TRANSISTOR 0.2A 0.15W -40/+125C
R1 RES THICK FILM CHIP 1206 10R 5% 0.25W
R2 R6 R11 RES THICK FILM CHIP 0603 100R 5% 0.1W
R3 R8 R14 R15 R19 VARISTOR BOURNS MLE SERIES CG0402MLE-18G 18V
R4 R5 RES THICK FILM CHIP 0603 22R 5% 0.1W -55/+125C
R7 RES THICK FILM CHIP 0603 1R0 5% 0.1W
R9 R28 RES THICK FILM CHIP 0603 51R 1% 0.063W
R10 RES THICK FILM CHIP 0402 220R 5% 0.1W
R12 RES THICK FILM CHIP 0402 2K2 5% 0.1W
R13 R24 R27 RES THICK FILM CHIP 0603 100K 5% 0.1W
R29 RES THICK FILM CHIP 0603 1K0 5% 0.1W
S1 S2 SWITCH SPST ON 1POL TYCO -40/+85C
S3 2 WAY SUB-MINIATURE SLIDE SWITCH SMD JS SERIES – SPDT -40/+85C
U1 USB DATA LINE PROTECTION ST USBLC6-2SC6 SOT23-6
U2 U4 LOW DROPOUT REGULATOR LINEAR LT1962 MS8 3.3V 0.3A
U3 U5 U9 TINY LOGIC UHS BUFFER OE_N ACTIVE LOW FAIRCHILD NC7SZ125 SC70
U6 RS-232 TRANSCEIVER 1MBIT 3-5,5VOLT TRSF3223 – VQFN20 5.5V 5.5V -40/+85C
U7 TINY LOGIC ULP-A 2-INPUT AND GATE 1.45X1.0 6-LEAD MICROPAK -40/+85C
Table 6: EVB-M8T component list

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9Schematic
Figure 7: Schematic EVK-M8T: DNI=TRUE in the schematic means: Component not installed

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10 Battery replacement
To replace the battery (Number 5 in Figure 8), open the unit (unscrew four screws on the front panel).
Figure 8: EVK-M8T battery location

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11 Troubleshooting
My application (e.g. u-center) does not receive anything
Check whether the blue LED on the evaluation unit is blinking. Also make sure that the USB cable is
properly connected to the evaluation unit and the PC. By default, the evaluation unit outputs NMEA
protocol on Serial Port 1 at 9600 Bd, or on the USB.
My application (e.g. u-center) does not receive all messages
When using UART, make sure the baud rate is sufficient. If the baud rate is insufficient, GNSS
receivers based on u-blox M8 GNSS technology
will skip excessive messages. Some serial port
cards/adapters (i.e. USB to RS232 converter) frequently generate errors. If a communication error
occurs while u-center receives a message, the message will be discarded.
My application (e.g. u-center) loses the connection to the GNSS receiver
u-blox M8 positioning technology and u-center both have an autobauding feature. If frequent
communication errors occur (e.g. due to problems with the serial port), the connection may be lost.
This happens because u-center and the GNSS receiver both autonomously try to adjust the baud rate.
Do not enable the u-center autobauding if the GNSS receiver has the autobauding flag enabled.
The COM port does not send any messages
Be sure that the slide switch at the front panel is set to I2C and not SPI. In SPI Mode the RS232 pins
on the DB9 connector are switched off and the RxD and TxD output at the front panel are used for SPI
(MISO, MOSI).
☞NOTE: After changing the slide switch, always reset the EVK; if not, the change will not take place.
Some COM ports are not shown in the port list of my application (e.g. u-center)
Only the COM ports that are available on your computer will show up in the COM port drop down list.
If a COM Port is gray, another application running on this computer is using it.
The position is off by a few dozen meters
u-blox M8 GNSS technology starts up with the WGS84 standard GNSS datum. If your application
expects a different datum, you’ll most likely find the positions to be off by a few dozen meters. Don’t
forget to check the calibration of u-center map files.
The position is off by hundreds of meters
Position drift may also occur when almanac navigation is enabled. The satellite orbit information
retrieved from an almanac is much less accurate than the information retrieved from the ephemeris.
With an almanac only solution, the position will only have an accuracy of a few kilometers but it may
start up faster or still navigate in areas with obscured visibility when the ephemeris from one or
several satellites have not yet been received. The almanac information is NOT used for calculating a
position, if valid ephemeris information is present, regardless of the setting of this flag.
In NMEA protocol, position solutions with high deviation (e.g. due to enabling almanac navigation) can
be filtered with the Position Accuracy Mask. UBX protocol does not directly support this since it
provides a position accuracy estimation, which allows the user to filter the position according to his
requirements. However, the ‘Position within Limits’ flag of the UBX-NAV-STATUS message indicates
whether the configured thresholds (i.e. P Accuracy Mask and PDOP) are exceeded.
TTFF times at startup are much longer than specified
At startup (after the first position fix), the GNSS receiver performs an RTC calibration to have an
accurate internal time source. A calibrated RTC is required to achieve minimal startup time.
Before shutting down the receiver externally, check the status in MON-HW in field ‘Real Time Clock
Status’. Do not shut down the receiver if the RTC is not calibrated.

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The EVK-M8T does not meet the TTFF specification
Make sure the antenna has a good sky view. An obstructed view leads to prolonged startup times. In
a well-designed system, the average of the C/No ratio of high elevation satellites should be in the
range of 40 dBHz to about 50 dBHz. With a standard off-the-shelf active antenna, 47 dBHz should
easily be achieved. Low C/No values lead to a prolonged startup time.
The EVK-M8T does not preserve the configuration in case of reset
u-blox M8 GNSS technology uses a slightly different concept than most other GNSS receivers do.
Settings are initially stored to volatile memory. In order to save them permanently, sending a second
command is required. This allows testing the new settings and reverting to the old settings by
resetting the receiver if the new settings aren’t good. This provides safety, as it is no longer possible
to accidentally program a bad configuration (e.g. disabling the main communication port).
The EVK-M8T does not work properly when connected with a GNSS simulator
When using an EVK together with a GNSS simulator, please pay attention to proper handling of the
EVK. A GNSS receiver is designed for real-life use, i.e. time is always moving forward. By using a GNSS
simulator, the user can change scenarios, which enables jumping backwards in time. This can have
serious side effects on the performance of GNSS receivers.
The solution is to configure the GPS week rollover to 1200 (as indicated in Figure 9), which corresponds
to Jan 2003. Then, issue the Cold Start command before every simulator test to avoid receiver
confusion due to the time jumps.
Figure 9: Configuration instruction for using the EVK with a GNSS simulator
Power Save Mode and USB
For communication in Power Save Mode, use the RS232.
The EVK-M8T receives GPS and GLONASS
Use u-center, version 7.02 or newer (EVK-M8). Message UBX-CFG-GNSS allows switching on and off
the supported GNSS.

EVK-M8T - User Guide
UBX-14041540 - R05 Common evaluation pitfalls Page 20 of 22
Early Production Information
12 Common evaluation pitfalls
•A parameter may have the same name but a different definition. GNSS receivers may have a
similar size, price and power consumption, but can still have different functionalities (e.g. no
support for passive antennas, different temperature range). Also, the definitions of hot, warm,
and cold start times may differ between suppliers.
•Verify design-critical parameters; do not base a decision on unconfirmed numbers from
datasheets.
•Try to use identical or at least similar settings when comparing the GNSS performance of different
receivers.
•Data that has not been recorded at the same time and the same place should not be compared.
The satellite constellation, the number of visible satellites, and the sky view might have been
different.
•Do not compare momentary measurements. GNSS is a non-deterministic system. The satellite
constellation changes constantly. Atmospheric effects (i.e. dawn and dusk) have an impact on
signal travel time. The position of the GNSS receiver is typically not the same between two tests.
Comparative tests should therefore be conducted in parallel by using one antenna and a signal
splitter; statistical tests shall be run for 24 hours.
•Monitor the carrier-to-noise ratio. The average C/No ratio of the high elevation satellites should be
between 40 dBHz and about 50 dBHz. A low C/No ratio will result in a prolonged TTFF and more
position drift.
•When comparing receivers side by side, make sure that all receivers have the same signal levels.
The best way to achieve this is by using a signal splitter. Comparing results measured with
different antenna types (with different sensitivity) will lead to incorrect conclusions.
•Try to feed the same signal to all receivers in parallel (i.e. through a splitter); the receivers won’t
have the same sky view otherwise. Even small differences can have an impact on the accuracy.
One additional satellite can lead to a lower DOP and less position drift.
•When doing reacquisition tests, cover the antenna in order to block the sky view. Do not unplug
the antenna since the u-blox M8 positioning technology continuously performs a noise calibration
on idle channels.