SOM-351U Information Sheet
C-V2X mPCIe System-On-Module, PC5 US stack, V2Xcast®
Overview
Unex’s SOM-351U is an innovative 3GPP C-V2X (LTE-V2X) PC5 System-On-Module that is designed to meet the rising market demand for easy-to-use V2X units in connected vehicles, intelligent transportation system (ITS), smart cities, smart farming, mining and port industry and to facilitate the development of mass-market solutions. Integrated with automotive-grade multi-core processor, RF, eHSM, RAM, flash, GNSS, PC5 US stack and V2Xcast® service, SOM-351U acts as a self-contained V2X system-on-module that enables V2X ecosystem on various platforms. Featuring V2Xcast® – a highly integrated and modular communication framework, SOM-351U supports rapid scalability on application host without sacrificing quality, making it an ideal V2X module of devices such as On-Board Unit (OBU), Roadside Unit (RSU), Telematics Box (T-Box) or Network Access Device (NAD).
Feature
- Pre-integrated firmware contains IEEE WAVE stack, Security and POTI.
- A rich SDK containing SAE J2735 messages, APIs and example codes accelerates development of innovative V2X applications.
- mPCIe design and V2Xcast® software support easy migration between DSRC and LTE-V2X PC5 without any hardware change on the application host.
- Integrated and modular V2X subsystem allows expandable applications for sensor fusions and AI applications with ease.
- External Molex connector provides all I/O pins for direct deployment on the existing host.
Specifications
Chipset |
|
---|---|
Operation System | Linux Yocto |
Form Factor | PCI Express Mini Card (Mini PCIe) |
Host Interface | USB 2.0 |
Preloaded Firmware | LTE-V2X PC5 US stack including IEEE WAVE stack and SCMS client |
Development Tool |
V2Xcast® SDK*, including APIs and SAE J2735 facility layer messages *. the SDK supports X86 32-bit and ARMv7-a 32-bit library, others by project base |
Hardware Security |
|
C-V2X (LTE-V2X) |
|
GNSS |
|
Operation Power | 5V: Imax=2A (during RF transmission, usually less than 2ms), Ityp=0.7A 3.3V: Imax=110mA, Ityp=105mA (preliminary data) |
On-board Interface |
RF interfaces:
|
Antenna |
|
ESD design | ESD protects all ports in ESD events. (IEC 61000- 4-2 Level 4, Contact ±8kV, Air ±15kV) |
Operation Temperature Range | ambient: -40ºC ~ +85ºC |
Storage Temperature Range | -45ºC ~ +90ºC |
Operating Humidity | 10% – 95%, non-condensing |
StorageHumidity | max. 95%, non-condensing |
Dimension | 50.95 mm(L) x 38.5 mm(W) x 11.7 mm (H) (preliminary data) |
Environment-Friendly Compliance | REACH and RoHS |
Software
Unex SOM-351U enables ease of V2X software development through its V2Xcast® technology. V2Xcast is a highly integrated and developer friendly software development kit for V2X communication. The solution provides ready-to-use V2X communication services for V2X applications, users can significantly cut time-to-market with less development and testing cost.
It includes two parts – V2Xcast Service and V2Xcast SDK.
V2Xcast SDK
Deploy V2Xcast SDK in your application host, it includes APIs to get the services from V2Xcast Service and the main functions of facility layer(J2735), such as message encoder/decoder and example code.
V2Xcast Service
V2Xcast Service image resides in SOM-351U, it combines IEEE WAVE stack, SCMS client and POTI. V2X communication protocols will be easily enabled via configuration profile input without any programming.
Security
A self-contained and highly integrated V2X system-on-module capable of highly secure V2X applications.
Security functions provided by V2Xcast® are designed based on a highly secure HSM (Hardware Security Module).
The highly secure HSM with FIPS 140-2 Level 3 certification is embedded in SOM-351U.
Cryptographic processor eliminates bottlenecks, maximizes application performance and offload CPU’s computation. To protect your sensitive cryptographic keys in a high-assurance key vault, the design provides leverage a keys-in-hardware solution. With the keys-in-hardware solution, all the cryptographic operations are inside HSM and those keys never leave the HSM.
Input Output Interface
mPCIe Pin Definition and Function
Row | Pin | Symbol | Type | Description | Status |
---|---|---|---|---|---|
0 | 1 | WAKE# | O | Open drain active low signal. This signal is used to wake up the host. | NC |
0 | 3 | 5V | P | 5V/2A Power Input (originally reserved) | Proprietary |
0 | 5 | 5V | P | 5V/2A Power Input (originally reserved) | Proprietary |
0 | 7 | CLKREQ# | O | Reference clock request signal | NC |
0 | 9 | GND | G | ||
0 | 11 | REFCLK- | I | PCI Express differential reference clock (100 MHz) | NC |
0 | 13 | REFCLK+ | I | PCI Express differential reference clock (100 MHz) | NC |
0 | 15 | GND | G | ||
0 | – | KEY | – | Mechanical Key | |
0 | 17 | UART_RX | I | UART receive data input (originally reserved) | Proprietary |
0 | 19 | UART_TX | O | UART transmit data output (originally reserved) | Proprietary |
0 | 21 | GND | G | ||
0 | 23 | PERn0 | I | PCI Express RX – | NC |
0 | 25 | PERp0 | I | PCI Express RX + | NC |
0 | 27 | GND | G | ||
0 | 29 | GND | G | ||
0 | 31 | PETn0 | O | PCI Express TX – | NC |
0 | 33 | PETp0 | O | PCI Express TX + | NC |
0 | 35 | GND | G | ||
0 | 37 | GND | G | ||
0 | 39 | 3.3 Vaux | P | Max 1100mA | |
0 | 41 | 3.3 Vaux | P | Max 1100mA | |
0 | 43 | GND | G | ||
0 | 45 | 5V | P | 5V/2A Power Input (originally reserved) | Proprietary |
0 | 47 | 5V | P | 5V/2A Power Input (originally reserved) | Proprietary |
0 | 49 | 1PPS | I | GNSS 1 pulse per second input (GATEWORKS standard, originally reserved) | Proprietary |
0 | 51 | TAMPER# | I | 0=Tampering, 1=Normal operation (PD) | Proprietary |
1 | 2 | 3.3 Vaux | P | Max 1100mA | |
1 | 4 | GND | G | ||
1 | 6 | 1.5 Volt | P | Max 500mA | NC |
1 | 8 | UIM PWR | O | SIM Card | NC |
1 | 10 | UIM_DATA | I/O | SIM Card | NC |
1 | 12 | UIM_CLK | O | SIM Card | NC |
1 | 14 | UIM_RESET | O | SIM Card | NC |
1 | 16 | UIM_VPP | O | SIM Card | NC |
1 | – | KEY | – | Mechanical Key | |
1 | 18 | GND | G | ||
1 | 20 | W_DISABLE# | I | Disable wireless communications (Internally pulled up. Active LOW) | NC |
1 | 22 | PERST# | I | Module Reset (Internally pulled up. Active LOW, pulse) | |
1 | 24 | 3.3 Vaux | P | Max 1100mA | |
1 | 26 | GND | G | ||
1 | 28 | 1.5Volt | P | Max 500mA | NC |
1 | 30 | SMB CLK | I | SMBus clock signal compliant to the SMBus 2.0 specification | NC |
1 | 32 | SMB Data | I/O | SMBus data signal compliant to the SMBus 2.0 specification | NC |
1 | 34 | GND | G | ||
1 | 36 | USB_D- | I/O | USB 2.0 differential data (-) | |
1 | 38 | USB_D+ | I/O | USB 2.0 differential data (+) | |
1 | 40 | GND | G | ||
1 | 42 | LED_WWAN# | O | Open drain, active low, max 9mA | NC |
1 | 44 | LED_WLAN# | O | Open drain, active low, max 9mA | NC |
1 | 46 | LED_WPAN# | O | Open drain, active low, max 9mA | NC |
1 | 48 | 1.5Volt | P | Max 500mA | NC |
1 | 50 | GND | G | ||
1 | 52 | 3.3 Vaux | P | Max 1100mA |
I/O Cable Pin Definition

Function | Pin | Name | Type | Level | Description |
---|---|---|---|---|---|
Power | 1 | 5V | P | 5 | 5V power |
UART | 2 | RXD | I | 3.3 | UART RXD |
UART | 3 | TXD | O | 3.3 | UART TXD |
Reset | 4 | TXD | I | 3.3 | System reset (active LOW) Min assertion time: 10ms |
1PPS | 5 | 1PPS | I | 3.3 | 1PPS |
Tamper | 6 | TAMPER# | I | 3.3 | Tamper switch signal (active LOW) |
Ground | 7 | GND | G | Ground |
DIP Switch

Function | Position | Name | Description |
---|---|---|---|
Power | 1 | 5V_SW | Connect 3.3V to a NMOS gate which controls 5V power. ON: 5V power from mPCIe OFF: 5V power from cable5V power |
UART | 2 | RXD_SW | ON: UART RXD from mPCIe OFF: UART RXD from cable |
UART | 3 | TXD_SW | ON: UART TXD from mPCIe OFF: UART TXD from cable |
Reset | 4 | EX_RSTn_SW | ON: CR2 reset from mPCIe OFF: CR2 reset from cable |
1PPS | 5 | 1PPS_SW | ON: 1PPS from mPCIe OFF: 1PPS from cable |
Tamper | 6 | TAMPER#_SW | ON: TAMPER# from mPCIe OFF: TAMPER# from cable |
Trigger Mode | 7 | TRIGGER_SW | ON: Trigger when tamper SW close to GND (1K PU) OFF: Trigger when tamper SW open from 3V3 (30K PD) |
Boot Strapping | 8 | BOOT_SW | ON: Boot from NAND (3K PD) OFF: Boot from USB0 (Open) |