Hardware Reference

ALPON X4 physical layout & I/O

Pinouts, ports, indicators, and electrical characteristics for every externally accessible interface on the ALPON X4 industrial edge computer. Use this reference to wire the device, drive its GPIO from software, and plan field installations. Built on Raspberry Pi.

Raspberry Pi CM4 1× Gigabit + 1× 100 Mbps Ethernet 2× USB 2.0 HDMI 2.0 / 4Kp30 RJ45 GPIO 9–30 V DC PoE+ (variant)

ALPON X4 · Hardware Reference · Physical Layout & I/O · Updated 2026-05-21

What I/O does the ALPON X4 expose?

The ALPON X4 exposes 3 power inputs (USB-C PD, 9–30 V DC terminal, optional PoE+), 1× Gigabit Ethernet and 1× 100 Mbps Ethernet, 2× USB 2.0 (1 A shared), HDMI 2.0 for display up to 4Kp30, an RJ45 GPIO Add-on port (I²C / UART / SPI at 3.3 V logic), 4 LED indicators, 2 user buttons, and 2 DIP switches for watchdog and image-flash mode.

Device layout

The ALPON X4 is housed in a fanless aluminum enclosure. All I/O is split between the front face (power, USB, display, indicators) and the rear face (Ethernet, GPIO, antennas, switches). Click any image to enlarge.

Front face

1PB1 · user push button

24× LEDs · Power, Connection, Cellular, RGB

3USB Type-C PD · power input

4Screw Terminal · 9–30 V DC input

5HDMI 2.0 · up to 4Kp30 display

62× USB 2.0 · 1 A shared budget

Rear face

7SW1, SW2 · watchdog & boot/burn DIP switches

8PB2 · user push button

9ETH · 100 Mbps Ethernet port

10ETH/G · 1 Gbps Ethernet (PoE+ on PoE variants)

11GPIO Add-on Port · RJ45, not Ethernet

Enclosure

12Antennas · 2× LTE, 1× GNSS, 1× Wi-Fi/Bluetooth (SMA)

13Mounting Holes · 2× 4 mm for DIN rail or wall mount

14Heatsink · finned aluminum top face, passive cooling

Mechanical specifications

Dimensions

111.16 × 99.9 × 33 mm

without antennas

Weight

~457 g

~1 lb

Enclosure

Aluminum, fanless

passive cooling

Protection

IP40

dust-protected

Operating temp

-20 to +60 °C

-4 to +140 °F

Storage temp

-40 to +85 °C

long-term

Humidity

Up to 95%

non-condensing

Mounting

DIN / Wall

2× 4 mm holes

Need mounting templates or dimension drawings?

Mounting templates, hole patterns, and dimension files are on the Power & Mounting page.

Open Power & Mounting

Power input

The ALPON X4 accepts power from three independent sources. There is no hard priority between inputs: the device draws from the source with the highest voltage. All inputs pass through ideal-diode protection.

The device must be operated with only one power input at a time. Connecting two or more power sources simultaneously is not recommended in production deployments — use a single source to simplify failure analysis and avoid ground loops.

ALPON X4 three power input options: USB-C PD, screw terminal, and PoE+ — Three available power input options on the ALPON X4.

USB Type-C PD

Sink-only USB-PD port. Does not provide USB data or output power during normal operation. USB data is available only when SW2 is set to Burn (image flashing) mode.

USB Type-C PD — specifications

Recommended adapter 27 W minimum at 15 V (USB PD)

Supported PD profile 15 V / 1.8 A (27 W)

PD controller CYPD3177-24LQXQ

Mode Sink only (no power output)

USB data Available only while SW2 = Burn

Powering the device at 5–12 V via USB-C forces the system into Restricted Mode to prevent brownout.

Screw terminal (9–30 V DC)

The recommended input for industrial edge computing deployments. The 3-pin terminal includes hardware reverse-polarity protection: swapped wiring will not damage the device, but it will not power on either.

Screw terminal — specifications

Input voltage 9 V to 30 V DC

Minimum power 27 W

Typical adapter 12 V or 24 V DC, 30 W

Reverse polarity protection Yes (hardware)

Pinout (3-pin block) Pin 1 Chassis Ground · Pin 2 Negative (−) · Pin 3 Positive (+)

ALPON X4 3-pin screw terminal block pinout: Pin 1 chassis ground, Pin 2 negative, Pin 3 positive — Terminal block polarity, left to right: Chassis, −, +.

Power over Ethernet (PoE+)

PoE+ is available only on PoE-variant SKUs. The PoE+ module is built into the device and cannot be added separately. When present, PoE+ is wired to the ETH/G port; the 100 Mbps ETH port does not accept PoE.

PoE+ — specifications

Standard IEEE 802.3at · PoE+ Class 4

Maximum delivered power 25 W

Compatible adapters PoE+ Class 4 only · passive PoE not supported

Supported port ETH/G (Gigabit) only

Restricted Mode

When USB-C is supplied at the 5–12 V range (below the 15 V PD profile), the device cannot guarantee enough headroom for every subsystem and enters Restricted Mode. Core compute and network paths stay online; high-draw peripheral rails are cut to prevent brownout.

Stays powered

Core subsystems keep running so the device stays reachable.

CM4 Compute Module
LTE Modem
ETH (100 Mbps)
ETH/G (1 Gbps)

Cut to save power

High-draw interfaces are disabled to prevent brownout.

USB 2.0 Ports
GPIO Add-on 5 V Rail
HDMI Display
Programmable RGB LED

Power consumption

Approximate consumption profile at 12 V DC input. Values depend on workload, attached peripherals, and active radios. A 27 W supply covers every supported configuration.

Profile

Range

Peak (W)

Idle (network standby)

~5 W

Typical workload

7 W – 14 W

LTE active transmit (added)

+2 W to +3 W

USB peripherals (combined)

Up to 5 W (1 A at 5 V)

GPIO Add-on 5 V rail

Up to 5 W (1 A at 5 V)

Maximum (full load)

27 W

Ethernet ports

Two RJ45 Ethernet ports with different link speeds and electrical topologies. Use both for WAN + LAN routing, dual-NIC redundancy, or isolating trusted and field segments.

ETH/G 1 Gbps PoE+

Gigabit Ethernet via USB-to-Gigabit bridge. Carries PoE+ on PoE-variant SKUs.

1 Gbps · USB-to-GbE bridge

ETH 100 Mbps

Native CM4 Ethernet port. 100 Mbps Fast Ethernet, no PoE.

100 Mbps · native CM4 MAC

On some PoE variants, the ETH/G port is replaced by the PoE+ input. Check your specific SKU before planning network topology.

USB 2.0 ports

Two USB 2.0 high-speed ports. Devices connected here are recognized as directly attached to the Raspberry Pi CM4 USB controller. Both ports share a combined 1 A power budget.

USB 2.0 — specifications

Standard USB 2.0 High-Speed (480 Mbps)

Routing Direct to Raspberry Pi CM4 USB controller

Shared power budget 1000 mA total at 5 V across both ports

Overcurrent behavior Power cut to both ports if 1 A is exceeded

Power recovery Full device shutdown and power-on required

You can connect a single device drawing up to 1 A, or two devices with a combined draw of no more than 1 A. If this limit is exceeded, power to both ports cuts off and a full device reboot is required to restore.

Display (HDMI 2.0)

Single HDMI 2.0 port driven directly by the CM4. Connects to a standard monitor with an HDMI cable. Supports up to 4K @ 30 Hz.

ALPON X4 HDMI 2.0 display port close-up, supports up to 4Kp30 — HDMI 2.0 display port, up to 4Kp30.

HDMI 2.0 — specifications

Standard HDMI 2.0

Maximum resolution 4K @ 30 Hz (4Kp30)

Audio HDMI audio pass-through

Driver CM4 HDMI 0 (direct)

Display detection runs at boot. For first-time setup or headless-to-monitor transitions, plug in HDMI before powering the device.

GPIO Add-on port (RJ45)

The GPIO Add-on port exposes six configurable CM4 pins over an RJ45 connector, providing I²C, UART, and SPI for ALPON Edge Add-on modules. Signals are 3.3 V logic routed through an on-board level converter for stability on long cable runs.

Although the connector is RJ45, this port is not Ethernet and not PoE-capable. Connecting it to a switch, router, or PoE injector will cause permanent hardware damage. Use only with compatible ALPON Add-on modules.

Pin assignment

RJ45 pin map — CM4 GPIO & alternates

Pin 1 GND · Ground

Pin 2 GPIO 12 · SPI5_CSn[0], UART4_TX, I2C2_SDA

Pin 3 GPIO 14 · SPI5_SIO[0], UART0_TX, I2C3_SDA

Pin 4 GPIO 13 · SPI5_SIO[1], UART4_RX, I2C2_SCL

Pin 5 GPIO 15 · SPI5_SCLK, UART0_RX, I2C3_SCL

Pin 6 GPIO 23 · I2C3_SCL

Pin 7 GPIO 22 · I2C3_SDA

Pin 8 5V OUT · 5 V output, max 1 A. Gated by GPIO 21 power switch

Electrical characteristics

Electrical & logic

Signal voltage 3.3 V logic (level converter on board)

5 V tolerance Pins are not 5 V tolerant

Power output 5 V at 1 A maximum (5 W)

Power switch enable GPIO 21 · must be HIGH before I/O

Fault detection GPIO 20 · HIGH normally, LOW on fault

The voltage level of all pins is 3.3 V. Pins are not 5 V tolerant. Driving them above 3.3 V can damage the CM4.

Enabling the port from software

The 5 V supply and signal I/O are gated by an on-board power switch. Drive GPIO 21 HIGH to activate the port, then read GPIO 20 to confirm no fault is asserted.

Control signals

ADDON_PWS_EN GPIO 21 · Drive HIGH to activate the port. I/O is inactive while LOW.

ADDON_PWS_FAULT GPIO 20 · Reads HIGH normally. Goes LOW on overcurrent or short-circuit events. Returns HIGH once the fault clears.

# 1. Enable the GPIO Add-on port power rail
pinctrl set 21 op dh      # drive GPIO 21 HIGH
pinctrl get 20            # read fault line, expect 1 (HIGH)

RJ45-to-terminal block adapter

When optional RJ45-to-terminal block adapters are attached, the GPIO port pins are mapped to screw-terminal positions for easy field wiring.

LED indicators

Four LEDs on the front face report system state. All LEDs are driven through the TCA6408A I²C I/O expander at address 0x20 on the I²C1 bus (SDA: GPIO 2, SCL: GPIO 3).

Programmable RGB

User

Expander P2 (R) · P3 (G) · P4 (B)

Logic Active LOW

Freely programmable. Set color by writing the corresponding R/G/B expander pins to LOW.

Cellular Status

System

Driver ALPON X4 OS

Colors Red / Yellow / Blue

Red: poor signal · Yellow: moderate · Blue: good connection.

Connection Status

System

Driver Sixfab Connect agent

Color Green

Lights green when the device is reachable via Sixfab Connect.

Power

Hardware

Source System power rail

Behavior Active HIGH

Turns white about 3 seconds after the device powers on.

The Programmable RGB LED is wired to expander pins P2 (Red), P3 (Green), and P4 (Blue). Set the corresponding pin LOW to turn that color on. A reference Python script that cycles through red, green, and blue is available as a GitHub Gist.

Push buttons

Two user-programmable buttons: PB1 on the front face and PB2 on the rear. Both lines are pulled HIGH by default and read LOW while pressed. Both can be assigned to different functions in software.

Button mapping

PB1 (front) GPIO 5 · Pulled HIGH · LOW when pressed · user-defined action

PB2 (rear) GPIO 6 · Pulled HIGH · LOW when pressed · user-defined action

Watchdog & Boot/Burn switches

Two DIP switches sit under a silicone cap on the rear face. Both ship OFF by default and should remain OFF during normal operation. Use a pointed tool to lift the cap from its notch.

SW1 · Watchdog

OFF (default) Watchdog active

ON Watchdog inactive

SW2 · Boot / Burn

OFF (default) Boot · normal operating mode

ON Burn · CM4 image flash mode

SW1 · Hardware watchdog

The hardware watchdog monitors device operation independently of the OS. When active (SW1 OFF), the device resets in case of failure. The watchdog runs on dedicated logic and cannot be disabled in software — only by physically toggling SW1.

SW2 · Boot / Burn mode

SW2 selects between normal operation (Boot) and CM4 image flashing over USB-C (Burn). In Burn mode, the USB-C port exposes the CM4 flashing interface to a host PC.

The device must be completely powered off when switching between Boot and Burn modes. Both switches are set to OFF by default from the factory and no changes are needed during normal operation. If either switch has been changed, set both back to OFF before powering the device. Toggling switches in modes other than Boot and Burn can prevent the device from achieving maximum uptime.

If an image is damaged or needs reflashing, contact Sixfab support before attempting the flash. Trying to reflash the image without guidance may cause more issues.

Antenna connectors

Four SMA connectors on the enclosure carry the wireless interfaces. Labels on the enclosure identify each port.

ALPON X4 antennas: G (GNSS), W (Wi-Fi), L x 2 (LTE Main + Diversity) — Antenna labels: G = GNSS · W = Wi-Fi · L × 2 = LTE.

SMA connector map

LTE Main Label L · SMA Female · Primary cellular RF path

LTE Diversity Label L · SMA Female · Rx diversity for improved link budget

GNSS / GPS Label G · SMA Female · Active antenna · must face the sky

Wi-Fi / Bluetooth Label W · SMA Male (RP-SMA) · 2.4 GHz + 5 GHz

The Wi-Fi port uses a male (RP-SMA) connector; GNSS and both LTE ports use female connectors. Supplied antennas are keyed accordingly. Verify thread compatibility before forcing a connection.

Radiation patterns & certified bands

LTE band list, antenna gain, and certified RF specs.

Open page

Internal bus topology

How each external interface maps back to the CM4. Useful for diagnosing throughput limits and shared-rail behavior.

Interface → CM4 mapping

USB Port 1 + 2 Native USB 2.0 · Direct to CM4 USB controller · 1 A shared budget

ETH (100 Mbps) Native Ethernet MAC · Direct to CM4 Ethernet controller

ETH/G (1 Gbps) USB-to-Gigabit bridge · Carries PoE+ on PoE variants

HDMI Display CM4 HDMI 0 · 4Kp30 maximum

LEDs I²C1 → TCA6408A @ 0x20 · Expander-driven

GPIO Add-on Port CM4 GPIO 12–15, 22, 23 · Gated by GPIO 21 power switch

Buttons CM4 GPIO 5 (PB1), GPIO 6 (PB2) · Pulled HIGH, LOW when pressed