Unex SOM-352 Series User manual

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Document Number
Unex-QSG-21-003
Revision
0.9
Authors
Nidor Huang
Quick Start Guide
for
SOM-352 Family
Product Variants
Model
Description
SOM-352
V2X mPCIe System-On-Module, 0A1
SOM-352EC
V2X mPCIe System-On-Module, V2Xcast® - C-V2X stack, Europe, 0A1
SOM-352ED
V2X mPCIe System-On-Module, V2Xcast® - ITS-G5 stack, Europe, 0A1
SOM-352UC
V2X mPCIe System-On-Module, V2Xcast® - C-V2X stack, USA, 0A1
SOM-352UD
V2X mPCIe System-On-Module, V2Xcast® - WAVE stack, USA, 0A1
Reviewers
Department
Name
Acceptance Date
Note
PD
Nidor Huang
2023/05/10
RD
P.C. Kang
2023/05/10
Modification History
Revision
Date
Originator
Comment
0.1
2021/08/19
Nidor Huang
Creating document
0.2
2021/10/13
Nidor Huang
Adding product variants
Adding limited warranty policies, safety guidelines
and product appearance
Adding reset and 1PPS guidelines
Adding software settings
Rearranging chapter order
Changing document type from HDG to QSG
0.3
2021/11/15
Nidor Huang
Updating J1.1 description
Adding antenna cable extraction instructions
Adding troubleshooting
0.4
2022/04/15
Nidor Huang
Adding GNSS antenna detection mechanism
0.5
2022/07/08
Nidor Huang
Modifying antenna cable extraction instructions
Adding tamper backup power description

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Revision
Date
Originator
Comment
0.6
2022/12/30
Nidor Huang
Changing model variants to SOM-352 family
Updating functional block diagram
Adding mPCIe Pin 46 BOOTSTRP
Adding 1PPS pin BSP description
0.7
2023/03/03
Nidor Huang
Adding V2X antenna detection function
Updating Unex BSP interface settings
Updating BOOTSTRP timing description
Updating product photos
0.8
2023/03/08
Nidor Huang
Updating Unex logo
Adding GNSS reset in Unex BSP interface settings
0.9
2023/05/10
Nidor Huang
Changing Ethernet over USB protocol to RNDIS

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TABLE OF CONTENTS
1. Objective...................................................................................................6
2. Reference .................................................................................................6
3. Limited Warranty Policy ............................................................................6
4. Safety Guidelines......................................................................................7
5. Product Appearance .................................................................................7
6. Functional Block Diagram.........................................................................8
7. Electrical Characteristics ..........................................................................9
7.1. Absolute Maximum Ratings .................................................................................. 9
7.2. Recommended Operating Conditions................................................................... 9
7.3. Power Consumption............................................................................................ 10
8. I/O Interfaces ..........................................................................................11
8.1. Antenna Connectors ............................................................................................11
8.1.1. 5.9GHz V2X .......................................................................................... 13
8.1.2. GNSS.................................................................................................... 14
8.2. Mini PCIe Card Pinout......................................................................................... 15
8.3. I/O Cable Pinout.................................................................................................. 17
8.4. DIP Switch........................................................................................................... 18
9. Design-in Guidelines...............................................................................19
9.1. Power Line Traces .............................................................................................. 19
9.2. Power Sequence................................................................................................. 20
9.3. Brown Out ........................................................................................................... 20
9.4. Grounding ........................................................................................................... 20
9.5. USB Data Lines................................................................................................... 20
9.6. Serial Port ........................................................................................................... 21
9.7. Reset ................................................................................................................... 22
9.8. 1PPS ................................................................................................................... 22
9.9. BOOTSTRP ........................................................................................................ 23
9.10. Tamper Detection (Optional) ............................................................................... 23
9.10.1. Production Mode................................................................................... 24
9.10.2. Test Mode ............................................................................................. 24
9.11. Thermal Management ......................................................................................... 25
9.12. Firmware Upgrade .............................................................................................. 25
9.12.1. Manual control ...................................................................................... 25
8.1.2.1. GNSS Antenna Detection............................................................. 14
9.10.1.1. Normal Mode................................................................................ 24
9.10.1.2. Standby Mode .............................................................................. 24

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9.12.2. Host GPIO control................................................................................. 26
10. Dimensions and Weight ..........................................................................26
10.1. Component Keep Out Area ................................................................................. 27
11. Software Settings....................................................................................28
11.1. Verifying the Integration with a Host System ...................................................... 28
11.1.1. Windows 10/11...................................................................................... 28
11.1.2. Linux ..................................................................................................... 29
12. Troubleshooting ......................................................................................30
12.1. Repetitive Resetting When Using 3.3V Single Voltage Supply .......................... 30
12.2. No Response After Applying Power .................................................................... 30
LIST OF FIGURES
Figure 1: SOM-352 series appearance ..................................................................................... 8
Figure 2: Functional block diagram ........................................................................................... 8
Figure 3: Antenna connectors.................................................................................................. 12
Figure 4: Antenna cable extraction tool ................................................................................... 13
Figure 5: V2X antennas EX-55/EX-53..................................................................................... 13
Figure 6: I/O Cable mating component P/N ............................................................................ 18
Figure 7: Onboard DIP switch ................................................................................................. 18
Figure 8: USB data line routing example................................................................................. 21
Figure 9: External 1PPS input pins.......................................................................................... 23
Figure 10: Thermally conductive pad area .............................................................................. 25
Figure 11: SOM-352 dimensions ............................................................................................. 27
LIST OF TABLES
Table 1. Absolute maximum ratings........................................................................................... 9
Table 2. Recommended operating conditions ........................................................................... 9
Table 3. Dual voltage power consumption............................................................................... 10
Table 4. External cable power consumption.............................................................................11
Table 5. Single voltage power consumption .............................................................................11
Table 6: V2X antenna status.................................................................................................... 13
Table 7: GNSS antenna status ................................................................................................ 15
Table 8: SOM-352 mini PCIe row 0 pinout .............................................................................. 15
Table 9: SOM-352 mini PCIe row 1 pinout .............................................................................. 16
Table 10: I/O cable pinout........................................................................................................ 17
Table 11: DIP Switch Functions ............................................................................................... 19
Table 12: Dimensions and weight............................................................................................ 27
Table 13: Unex BSP interface settings .................................................................................... 28

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1. Objective
The purpose of this document is to provide necessary information to help setup and
installation of SOM-352 series products. To provide for safe installation and operation of
the equipment, read the safety guidelines at the beginning of this manual and follow the
procedures outlined in the following chapters before connecting power to SOM-352. Keep
this operating manual handy and distribute to all users, technicians and maintenance
personnel for reference.
2. Reference
•PCI Express Mini Card Electromechanical Specification 2.0/2.1
•I-PEX MHF Micro RF coax connector product series catalog
•HIM-10002-06EN: I-PEX MHF I Connector Instruction Manual
•Unex SOM-352 datasheet
•SOM-352 drawing 51-00009-00
•Unex’s documentation (in Unex’s software release package)
3. Limited Warranty Policy
Unex Technology Corporation selling the product warrants that commencing from the
date of shipment to customer and continuing for a period of twelve (12) months. This limited
warranty extends only to the original customer of the product. Customer's sole and
exclusive remedy and the entire liability of Unex under this limited warranty will be, at
Unex's option, return for repair to Unex's repair center with freight and insurance prepaid
or shipment of a replacement within the warranty period or a refund of the purchase price
if the hardware is returned to Unex. Unex’s obligations hereunder are conditioned upon the
return of affected hardware in accordance with Unex's service center's then-current Return
Material Authorization (RMA) procedures.
This warranty does not cover:
•Products found to be defective after the warranty period has expired.
•Products subjected to misuse or abuse, whether by accident or other causes.
Such product conditions will be determined by Unex at its sole and unfettered
discretion.
•Products damaged due to a natural disaster, including but not limited to

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lightning, flooding, earthquake, or fire.
•Software products.
•Products dismantled or opened by unauthorized persons. Please contact a
representative of Unex if you need advanced technical support.
•Products with an altered and/or damaged serial number.
•Loss of data or software.
•Products that have been updated, reworked, or improperly tested by the
Customer, or by a third party at the request of the Customer.
•Customized and original design manufacturer (ODM) products. The warranty
terms for customized and ODM products should be defined in the contract
that governs the project.
4. Safety Guidelines
•Keep working area clean and dry while assembling/installing.
•When operating under extreme temperature conditions, environmental control
measures (e.g., heating, cooling) should be considered.
•Make sure every accessory has been fastened, including the V2X antenna cables,
GNSS antenna cable, and the mPCIe socket latch/screws.
5. Product Appearance
The photos shown in this document may seem different from actual product. However,
the differences do not affect actual functionalities.

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Figure 1: SOM-352 series appearance
6. Functional Block Diagram
Figure 2: Functional block diagram
TOP
BOTTOM

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7. Electrical Characteristics
7.1. Absolute Maximum Ratings
Over operating free-air temperature range (unless otherwise noted).
Table 1. Absolute maximum ratings
Parameters
Conditions
Min.
Max.
Unit
Storage Temperature
-
-40
105
°C
Supply Voltage
mPCIe 5V
-0.3
6.0
V
mPCIe 3.3 Vaux
-0.3
3.9
V
V2X maximum input level
-
-
10
dBm
GNSS maximum input level
-
-
-10
dBm
Note: (1) Operation outside the Absolute Maximum Ratings may cause permanent device damage. Absolute
Maximum Ratings do not imply functional operation of the device at these or any other conditions
beyond those listed under Recommended Operating Conditions. If used outside the Recommended
Operating Conditions but within the Absolute Maximum Ratings, the device may not be fully functional,
and this may affect device reliability, functionality, performance, and shorten the device lifetime.
(2) All voltages are with respect to network GND.
7.2. Recommended Operating Conditions
Over operating free-air temperature range (unless otherwise noted).
Table 2. Recommended operating conditions
Parameters
Conditions
Min.
Typ.
Max.
Unit
Ta (Ambient operating temperature)
Free-air temp.
-40
25
85
°C
Supply voltage
mPCIe 5V
4.8
5.0
5.2
V
mPCIe 3.3 Vaux
3.0
3.3
3.6
V
VIL (Input low level voltage)
mPCIe 5V = 5.0V
-0.3
-
0.8
V
VIH (Input high level voltage)
mPCIe 5V = 5.0V
2.0
-
3.6
V
TAMPER#
2.0
-
3.3 Vaux
+0.3
V
RPU (Equivalent pull-up)
1PPS/UART *1
32
50
60
kΩ
PERST#/EX_RSTn
1.8
2.1
2.3
kΩ
TAMPER# *2
0.9
1.0
1.1
kΩ
RPD (Equivalent pull-down)
TAMPER# *3
32
50
60
kΩ
VOL (Output low level voltage)
IOL= 4mA *4
-
-
0.4
V
VOH (Output high level voltage)
IOH= 4mA *5
2.9
-
-
V

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Parameters
Conditions
Min.
Typ.
Max.
Unit
mPCIe 1PPS (P49) tolerance
Accuracy/Bias
-100
-
100
ns
Precision/Jitter
-30
-
30
ns
Pulse width
15
-
-
ns
V2X sensitivity
PER ≤ 10%
-92
-
-
dBm
PER ≤ 10%,
-40 - +85 °C
-82
-
-
dBm
V2X maximum input level
PER ≤ 10%
-
-
-30
dBm
V2X adjacent channel rejection
-
13
-
-
dB
V2X non-adjacent channel rejection
-
29
-
-
dB
V2X output power
Spectrum mask
Class C
-
-
20
dBm
GNSS sensitivity (C/N0)
Acquisition
22
30
45
dB-
Hz
GNSS antenna bias
IANT ≤ 20mA
3.0
-
3.3
V
GNSS antenna detection current
IANT *6
12
-
58
mA
GNSS maximum total external gain
Gain/loss combined
-
-
24
dB
Note: *1: UART = UART_RX (mPCIe P17) / UART_TX (mPCIe P19) / RXD (Molex P2) / TXD (Molex P3)
*2: TRIGGER_SW (SW1.7) = ON
*3: TRIGGER_SW (SW1.7) = OFF
*4: IOL = Low level output current (UART_TX)
*5: IOH = High level output current (UART_TX)
*6: IANT under Min. = OPEN; IANT over Max. = SHORT; IANT between Min/Max. = NORMAL.
7.3. Power Consumption
SOM-352 can be powered in three different ways: dual voltage (5V/3.3V), external
cable (5V/3.3V), and single voltage (3.3V). The data listed in table 3, 4, and 5 serve only
as a reference for system integrators. The actual conditions will vary depending on firmware
version and user applications.
Table 3. Dual voltage power consumption
Condition
Power Consumption (A)
Temp.
Power Source
Voltage (V)
Low *1
Typical *2
High *3
25°C
5V *4
5
0.34
0.40
2.0
3.3 Vaux *5
3.3
0.100
0.105
0.110
85°C
5V *4
5
0.38
0.44
2.0
3.3 Vaux *5
3.3
0.105
0.110
0.115

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Condition
Power Consumption (A)
Note: *1: CPU idle and V2X stack loaded.
*2: CPU 50% and V2X transmitting 400 bytes at 20dBm every 100ms.
*3: Hardware upper limit.
*4: From mini PCIe 5V (pin 3, 5, 45, 47)
*5: From mini PCIe 3.3 Vaux (pin 2, 24, 39, 41, 52)
Table 4. External cable power consumption
Condition
Power Consumption (A)
Temp.
Power Source
Voltage (V)
Low *1
Typical *2
High *3
25°C
5V *4
5
0.34
0.40
2.0
3.3 Vaux *5
3.3
0.100
0.105
0.110
85°C
5V *4
5
0.38
0.44
2.0
3.3 Vaux *5
3.3
0.105
0.110
0.115
Note: *1: CPU idle and V2X stack loaded.
*2: CPU 50% and V2X transmitting 400 bytes at 20dBm every 100ms.
*3: Hardware upper limit.
*4: From Molex 7 pin connector (pin 1)
*5: From mini PCIe 3.3 Vaux (pin 2, 24, 39, 41, 52)
Table 5. Single voltage power consumption
Condition
Power Consumption (A)
Temp.
Power Source
Voltage (V)
Low *1
Typical *2
High *3
25°C
3.3 Vaux *4
3.3
0.60
0.70
3.0
85°C
3.3 Vaux *4
3.3
0.70
0.77
3.0
Note: *1: CPU idle and V2X stack loaded.
*2: CPU 50% and V2X transmitting 400 bytes at 20dBm every 100ms.
*3: Hardware upper limit.
*4: From mini PCIe 3.3 Vaux (pin 2, 24, 39, 41, 52)
8. I/O Interfaces
8.1. Antenna Connectors
The SOM-352 mPCIe module is provided with three 50 Ω RF connectors (see FIGURE
3: ANTENNA CONNECTORS):
•two V2X antennas

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•one GNSS antenna
Receptacle connectors are I-PEX MHF I 20279-001E-03. For more information about
mating plug connectors, visit the website https://www.i-pex.com/product/mhf-I or for more
detail.
Figure 3: Antenna connectors
The antenna connection is one of the most important aspects in the full product design
as it strongly affects the RF performance. Connecting cables between the module and the
antenna must have 50 Ω impedance. If the impedance of the module is mismatched, RF
performance will be reduced significantly.
Please be careful when extracting the antenna cables from a SOM-352 module.
Extracting the connector by pulling the cable may cause damage on the antenna plug
assembly. It is recommended to extract the cable using a proper extraction tool suggested
by the cable plug manufacturer. For I-PEX plugs please use I-PEX 90192-001 or 90224-
001.
V2X1 ANT
V2X0 ANT
GNSS ANT

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Figure 4: Antenna cable extraction tool
Caution
1 Always use only the extraction tool recommended by the plug
manufacturer of your choice. It is possible to cause severe damage
on the receptacle if a third-party extraction tool is used. For
example, using an I-PEX tool on a HIROSE plug has been known to
lead to connector damages.
2 It is very important to keep the extraction tool at a vertical position
at all time, and apply only vertical pulling force on the tool. Applying
a non-vertical force or using the tool in a crowbar style will damage
not only the antenna connector but also other components in
proximity.
3 Please follow HIM-10002-06EN for more detailed instructions.
8.1.1. 5.9GHz V2X
The V2X antenna ports has a built-in antenna detection function (see TABLE 6). This
detection mechanism only works with Unex V2X antennas EX-55 or EX-53 antennas. EX-
55/EX-53 antennas are not included in SOM-352 product package and can be purchased
separately.
Table 6: V2X antenna status
Antenna Status
Value
Command
OPEN
616-1023
V2X0: cat /sys/bus/iio/devices/iio\:device0/in_voltage4_raw
V2X1: cat /sys/bus/iio/devices/iio\:device0/in_voltage5_raw
NORMAL
410-615
SHORT
0-409
Figure 5: V2X antennas EX-55/EX-53
1
2
3
EX-55
Gain: 5dBi
Radiation Pattern: Omni-directional
Application: Indoor/OBU
Connector: FAKRA-Z
EX-53
Gain: 7.6dBi
Radiation Pattern: Omni-directional
Application: Outdoor/RSU
Connector: Type N

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8.1.2. GNSS
For stable fix acquisition, at least 4 satellites with enough signal strength (C/N0 value
above 30 dB-Hz) are required. If the signal strength goes below 30 dB-Hz, the fix will
become unstable.
8.1.2.1. GNSS Antenna Detection
The antenna detection mechanism is a 2-step process: First check the signal strength.
If the signal strength drops to zero, then check the antenna status flag.
When all the C/N0 values becomes null, it means that the GNSS antenna or its cable
may either become detached or damaged. The GNSS antenna port has a built-in antenna
detection function. The detection mechanism is based on the current consumption of an
active antenna (IANT). If the active antenna consumes less current than 12 mA, then it is
considered as the OPEN status; if the antenna consumes more than 58 mA, then it is
considered as the SHORT status. Anything between 12-58 mA is considered as the
NORMAL status.
The GNSS 3.3V antenna bias will be continuously supplied in OPEN/NORMAL status.
Once the SHORT status is triggered, the SHORT flag will persist, and the 3.3V bias will be
turned off until the reset of the GNSS module. After the reset of the GNSS module, the
detection process will start all over again.
It is possible for a good active antenna to be reported OPEN because it consumes less
current than 12 mA, or a good passive antenna to be considered SHORT because it is DC
shorted (e.g., a slot antenna). However, as long as there are more than 4 satellites with
enough signal strength (C/N0 value above 30 dB-Hz), the GNSS is in good state.
The antenna status flag is reported in a proprietary NMEA message:
$PSTMANTENNASTATUS,<status>*<checksum><cr><lf>
where <status> can be:
•0 - The antenna current is in the normal range (NORMAL)
•1 - The antenna current is below the normal range (OPEN)
•2 - The antenna current is above the normal range (SHORT)

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Table 7: GNSS antenna status
Antenna
Status
Current
Consumption (mA)
3.3V bias
NMEA Sentence
OPEN
< 12
ON
$PSTMANTENNASTATUS,1*4C
NORMAL
between 12- 58
ON
$PSTMANTENNASTATUS,0*4D
SHORT
> 58
Turned OFF once triggered
$PSTMANTENNASTATUS,2*4F
8.2. Mini PCIe Card Pinout
There are 3 groups of pins in the SOM-352 mPCIe pinout:
4 Group 1: Proprietary pins, originally marked as reserved in mPCIe standard
interface
5 Group 2: Standard mPCIe pins used by SOM-352, including 3.3 Vaux, ground,
PERST#, and USB data lines
6 Group 3: Standard mPCIe pins but not used in SOM-352, marked NC
SOM-352 only needs group1 and group2 pins for normal operation. For maximize
compatibility with existing mPCIe modules on the market, it is suggested to connect all
three groups of pins to the mPCIe connector.
Please note that the I/O directions listed here are on the SOM-352 side. For designing
a system board mPCIe interface, the input and output direction must be reversed.
Table 8: SOM-352 mini PCIe row 0 pinout
Pin
Symbol
Type
Level (V)
Description
Note
1
NC
-
-
Not connected
3
5V
P
5
5V/2A power input
Proprietary
5
5V
P
5
5V/2A power input
Proprietary
7
NC
-
-
Not connected
9
GND
G
-
Ground
11
NC
-
-
Not connected
13
NC
-
-
Not connected
15
GND
G
-
Ground
-
KEY
-
-
Mechanical key
17
UART_RX
I (PU)
3.3
UART received data
Proprietary
19
UART_TX
O (PU)
3.3
UART transmitted data
Proprietary
21
GND
G
-
Ground
23
NC
-
-
Not connected
25
NC
-
-
Not connected
27
GND
G
-
Ground
29
GND
G
-
Ground
31
NC
-
-
Not connected
33
NC
-
-
Not connected

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Pin
Symbol
Type
Level (V)
Description
Note
35
GND
G
-
Ground
37
GND
G
-
Ground
39
3.3 Vaux
P
3.3
Powered by 5V: 115mA (max)
Powered by 3.3 Vaux: 3000mA (max)
41
3.3 Vaux
P
3.3
Powered by 5V: 115mA (max)
Powered by 3.3 Vaux: 3000mA (max)
43
GND
G
-
Ground
45
5V
P
5
5V/2A power input
Proprietary
47
5V
P
5
5V/2A power input
Proprietary
49
1PPS
I (PU)
3.3
GNSS 1PPS input (active HIGH)
Proprietary
51
TAMPER#
I
(PU/PD)
3.3
Tamper detection (active LOW)
PU/PD decided by SW1.7
TRIGGER_SW ON: 1KΩPU
TRIGGER_SW OFF: 32KΩPD (min)
Proprietary
Table 9: SOM-352 mini PCIe row 1 pinout
Pin
Symbol
Type
Level (V)
Description
Note
2
3.3 Vaux
P
3.3
Powered by 5V: 115mA (max)
Powered by 3.3 Vaux: 3000mA (max)
4
GND
G
-
Ground
6
NC
-
-
Not connected
8
NC
-
-
Not connected
10
NC
-
-
Not connected
12
NC
-
-
Not connected
14
NC
-
-
Not connected
16
NC
-
-
Not connected
-
KEY
-
-
Mechanical key
18
GND
G
-
Ground
20
NC
-
-
Not connected
22
PERST#
I (PU)
3.3
CRATON2 reset (2KΩ PU, active LOW)
Signal rising edge (0 →1) will reset
mPCIe module
24
3.3 Vaux
P
3.3
Powered by 5V: 115mA (max)
Powered by 3.3 Vaux: 3000mA (max)
26
GND
G
-
Ground
28
NC
-
-
Not connected
30
NC
-
-
Not connected
32
NC
-
-
Not connected
34
GND
G
-
Ground
36
USB_D-
I/O
0.4
USB data line -
38
USB_D+
I/O
0.4
USB data line +
40
GND
G
-
Ground
42
NC
-
-
Not connected
44
NC
-
-
Not connected
46
BOOTSTRP
I (PD)
3.3
BOOT_SW ON:
0 or NC: Boot from NAND
1: Boot from USB0 (DFU mode)
BOOT_SW OFF:
0/1/NC: Boot from USB0 (DFU mode)
Proprietary
48
NC
-
-
Not connected
50
GND
G
-
Ground

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Pin
Symbol
Type
Level (V)
Description
Note
52
3.3 Vaux
P
3.3
Powered by 5V: 115mA (max)
Powered by 3.3 Vaux: 3000mA (max)
8.3. I/O Cable Pinout
The I/O cable can help user to install SOM-352 on an existing mPCIe system board
without modifying the system board hardware.
Please note that the pinout listed here is seen from the SOM-352 side. For designing
an I/O cable interface on the system board, the input and output direction must be reversed.
Table 10: I/O cable pinout
Pin
Name
Type
Level (V)
Description
J1.1
5V
P
5
5V power, OR’ing with 3.3V single
voltage mode
J1.2
RXD
I
3.3
UART RXD (PU)
Internally tied with mPCIe P17
J1.3
TXD
O
3.3
UART TXD (PU)
Internally tied with mPCIe P19
J1.4
EX_RSTn
I
3.3
CRATON2 reset (PU)
Internally tied with mPCIe P22
J1.5
1PPS
I
3.3
1PPS (PU)
Internally tied with mPCIe P49
J1.6
TAMPER#
I
3.3
Active LOW
Internally tied with mPCIe P51
J1.7
GND
G
-
Ground
The 7-pin cable connector is Molex Pico-Lock system 504051-0701 and the contact is
504052-0098.

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Figure 6: I/O Cable mating component P/N
8.4. DIP Switch
The onboard DIP switch can help user to direct power and I/O signals from either
mPCIe interface or the I/O cable. The tamper signal trigger mode and firmware upgrade
can also be selected by user.
Figure 7: Onboard DIP switch
Please note that the in SW1.1 to SW1.6, the OFF position actually disconnects the
power/signal from the mPCIe pin, while the ON position ties mPCIe pins and I/O cable pins
together. In order to avoid interference and to keep 5V power from damaging your system
board, it is important to set the DIP switch to correct positions before connecting the I/O
cable.
DIP SW

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Switching of internal/external GNSS and 1PPS signal is not controlled by DIP switch.
Please see 9.8 1PPS for detailed instruction.
Table 11: DIP Switch Functions
Position
Name
ON Function
OFF Function
SW1.1
5V_SW
5V power from mPCIe
5V power from cable, or
3.3V single voltage mode
SW1.2
RXD_SW
UART RXD from mPCIe
UART RXD from cable
SW1.3
TXD_SW
UART TXD from mPCIe
UART TXD from cable
SW1.4
EX_RSTn_SW
CRATON2 reset from mPCIe
CRATON2 reset from cable
SW1.5
1PPS_SW
External 1PPS from mPCIe
External 1PPS from cable
SW1.6
TAMPER#_SW
TAMPER# from mPCIe
TAMPER# from cable
SW1.7
TRIGGER_SW
Trigger when tamper SW
close to ground (1KΩ PU)
Trigger with tamper SW
open from 3.3V (32KΩ PD)
SW1.8
BOOT_SW
Boot from NAND
Boot from USB0 (DFU)
9. Design-in Guidelines
The SOM-352 pinout is compatible with most standard PCIe mini card interfaces.
However, it may need to be fed with 5V DC power and connecting other I/O interfaces
through an external cable when installed on an existing mPCIe system board. A customized
PCIe mini card pinout can help user to get rid of the extra cable and to rely on the PCIe
mini card interface alone. A design-in system board solution may provide improved
reliability, simpler installation, and cost saving to the overall system.
9.1. Power Line Traces
•Power line traces should be as wide as possible, in order to reduce impedance of
these lines.
•Crossing by any other lines of upper or lower layer should also be avoided.
•The maximum power consumption occurs during RF transmission. A typical
transmitting frame lasts 1-2ms.
•It is recommended to keep the 5V supply current no less than 2A (continuous) to
keep RF performance from degradation.
•If the SOM-352 halts or resets while performing a V2X RF transmission, it is
recommended to add a bulk capacitor on the 5V trace near the mPCIe connector to

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lower the impedance of the 5V power rail.
9.2. Power Sequence
•5V should be supplied prior to 3.3 Vaux.
•If 3.3 Vaux is fed before 5V, user should toggle the EX_RSTn signal after 5V is
supplied.
•If it is intended to save power when the SOM-352 is not in use, it is suggested to
pull low the EX_RSTn/PERST# pin instead of cutting off 5V power. Once the
EX_RSTn/PERST# pin is pulled low, the SOM-352 will enter standby mode, and
the power consumption will reduce to 10mA in about 10 seconds.
9.3. Brown Out
•If the 5V power supply drops below 3.5V, the SOM-352 will enter standby mode.
•A SOM in standby mode will stay in this mode until reset.
•Once the power supply returns to normal, the SOM-352 can reboot into normal
operation with the rising edge of PERST# or EX_RSTn signal.
9.4. Grounding
•Ensure good GND connection between the ground of the module and the ground of
the system board.
•Grounding of the external components (e.g., capacitors) should be connected to
the same reference ground of the module and not just on the top layer, use more
than one via whenever possible to ensure good GND connection.
9.5. USB Data Lines
The SOM-352 mPCIe module includes a Universal Serial Bus (USB) transceiver, which
operates at USB high-speed (480 Mbits/s). It is compliant with the USB 2.0 specification
and can be used for control and data transfers as well as for diagnostic monitoring and
firmware upgrade.
The USB port is typically the main interface between the SOM-352 mPCIe module and
OEM hardware. Since the USB_D+ and USB_D- signals have a clock rate of 240 MHz, the
signal traces must be routed carefully. Minimize trace lengths, number of vias, and
capacitive loading.
The layout guidelines for the USB data lines (mPCIe pin 36, 38) is listed below. And a