Specifications
Sixfab Edge AI Expansion Board specifications
Electrical, mechanical, thermal, and software specifications for the Sixfab Edge AI Expansion Board for Raspberry Pi 5. Use it as the canonical reference when sizing power supplies, selecting M.2 modules, or designing custom enclosures around the under-board stack. Intelligented by DEEPX. Built on Raspberry Pi.
The Sixfab Edge AI Expansion Board for Raspberry Pi 5 is an under-board baseboard carrying a DEEPX DX-M1M (25 TOPS at INT8) or DX-M1ML (13 TOPS at INT8) NPU plus three M.2 slots (AI accelerator, NVMe SSD, LTE/5G modem) on a 88.46 × 89.19 mm footprint. The AI accelerator links to the Pi 5 over PCIe Gen 2/Gen 3 x1 through a 40 mm FFC; NVMe and cellular share an internal USB 3.2 Gen 1 (5 Gbps) hub. A single USB-C PD input (27 W minimum, 45 W recommended for the full stack) powers the entire system and back-powers the Pi 5 through pogo pins.
Quick reference
Headline figures at a glance. Scan this block first; full per-category detail follows below.
Technical specifications
Per-category breakdown of the Edge AI Expansion Board electrical, mechanical, and software specifications. Figures apply to both NPU variants unless otherwise noted.
dxrt-runtime
dtparam=pciex1_gen=3
/dev/sda)
sixfab-dx
dxrt-runtime
dxrt-cli · dxtop
Variants
The Edge AI Expansion Board ships with two NPU variants on the M.2-PCIE slot. They share the same PCB, the same triple-M.2 layout, the same connectors, and the same software stack. Only the NPU on the M.2 module changes.
sixfab-dx packagesixfab-dx packageThe driver detects the installed M.2 module automatically at boot. The practical differences are NPU compute throughput and on-module memory capacity, which together bound the maximum model size and per-stream resolution. NPU memory is exclusive to the accelerator: the Raspberry Pi 5 CPU cannot directly read or write it.
For published performance numbers with full methodology (model, resolution, runtime version, Pi 5 RAM), see the Sixfab Model Zoo and Custom Models (DXNN SDK) pages.
Connectors & slots
Five user-facing interfaces on the board: three M.2 slots, the PCIe FFC link to the Pi 5, and the USB-C PD power input. Plus a pogo-pin back-power array on the top surface, a nano SIM slot, and a USB-A passthrough for the internal USB Bridge.
Single power input for the entire stack. The board back-powers the Raspberry Pi 5 through pogo pins; the Pi 5's own USB-C port stays unused. Below 27 W the system shows a visible under-voltage warning and throttles.
RPI5 / EDGE_AI
Dedicated PCIe link between the Raspberry Pi 5 and the DEEPX DX-M1 in the M.2-PCIE slot. The RPI5-labelled end goes to the Pi 5's PCIe FPC port; the EDGE_AI-labelled end goes to the Expansion Board's FFC connector. Labels face outward, metal pins inward. A longer cable is not recommended.
The only slot wired to the dedicated PCIe link. Houses the DEEPX DX-M1 M.2 module. The included 3D-printed spacer sits between the module and the Expansion Board's mounting hole. Insert at 30° and finger-tighten the M2 screw.
/dev/sda
NVMe SSD slot routed through the on-board USB 3.0 hub and a Realtek USB-to-NVMe bridge. The OS sees a USB Mass Storage device, not a native NVMe block device. M.2 SATA modules are not supported.
M.2 Key-B slot for an LTE or 5G modem module, exposed to the OS over the internal USB 3.2 Gen 1 hub through the USB Bridge PCBA. The board carries no built-in antennas; the antenna connector type depends on the chosen modem module.
Four spring-loaded contacts on the top surface that press into 5V and GND pads on the underside of the Raspberry Pi 5 GPIO header. No data signals are routed through pogo pins; they carry power only. Spacer torque is critical for reliable contact.
Short USB-A bridge that connects the on-board hub to one of the Raspberry Pi 5's blue USB 3.0 ports. Mandatory for both the NVMe SSD and the LTE/5G modem to function. The Pi 5's remaining three USB ports (one USB 3.0, two USB 2.0) stay free for peripherals.
The Expansion Board has no dedicated fan connector; cooling runs from the Pi 5's own 4-pin JST-SH fan header. The Raspberry Pi 5 Active Cooler is electrically and functionally identical to a stand-alone configuration, so PWM speed control works out of the box.
Hardware developers integrating the Expansion Board into custom carrier designs work from the user-facing interfaces above only. There are no exposed debug UART, GPIO pass-through control, or user-configurable hardware bridges. The GPIO header on the Pi 5 is forwarded upward unchanged, so a standard top-mounted HAT can co-exist. See Pinout & GPIO.
LED indicators
The Expansion Board has four LEDs grouped near the edge of the PCB. One is for power; the other three follow the three data paths off the board (cellular network, USB-controller traffic, and the PCIe lane). The LEDs are hardware-driven and cannot be controlled programmatically. Detailed runtime telemetry lives in dxrt-cli and dxtop, see System Monitoring.
On when the Expansion Board is receiving valid USB-C PD input and its on-board rails are up. Off indicates no power, an under-voltage PSU, or a USB-C cable issue.
Driven by the LTE/5G modem in the CELLULAR slot. Indicates network registration and signal activity. Specific blink-vs-solid meaning is set by the modem module's firmware, refer to the installed module's datasheet for the exact decoding.
Activity on the internal USB 3.0 controller, typically the NVMe SSD via the Realtek bridge or the cellular modem's USB traffic. Flickers in step with bus activity.
Activity on the PCIe lane that feeds the DX-M1 NPU. Pulses during inference and other PCIe traffic.
Cooling
The DEEPX DX-M1 module and the NVMe SSD are the dominant heat sources on the stack. Cooling is delivered through the Raspberry Pi 5's own cooler, not a dedicated header on the Expansion Board.
Install the official Active Cooler on the Pi 5's 4-pin JST-SH fan header before stacking the Expansion Board underneath. PWM speed control works automatically. Best balance of airflow, noise, and Z-height for the assembled stack.
Apply a thermal pad and small heatsink directly to the DX-M1 module if active cooling is not desirable (silent enclosures, low-duty workloads). Verify the ~90 °C NPU throttle threshold is not reached under sustained inference via dxtop.
Standard off-the-shelf Pi 5 cases generally do not fit the stack; a custom enclosure with vents over the DX-M1 module and the NVMe SSD is required for sealed deployments. Verify thermal headroom at the target ambient before shipping.
The DX-M1 reduces clock rate when on-NPU temperature approaches roughly 90 °C. Live temperature is exposed by dxrt-cli -s and the running view in dxtop. Continuous throttling indicates insufficient cooling for the workload, so either reduce duty cycle, add active cooling, or improve enclosure airflow.
Signal integrity & ESD
PCIe FFC interface
The PCIe link runs the standard PCIe Gen 2/Gen 3 differential signaling between the Pi 5's BCM2712 SoC PCIe controller and the DEEPX NPU controller on the M.2 module. The 40 mm FFC is the qualified path; longer cables, different pitch, or third-party FFCs are not recommended because they introduce insertion loss and skew that the link margin was not designed for.
USB 3.2 Gen 1 internal hub
The NVMe and cellular slots share a 5 Gbps internal hub that connects to the Raspberry Pi 5 through the USB Bridge PCBA. The aggregate ceiling is the 5 Gbps bus, and the throughput envelope reported on the Storage card already accounts for 8b/10b encoding overhead and protocol management. Concurrent NVMe + cellular + AI workloads do not measurably degrade AI throughput, because the PCIe path to the NPU is independent.
ESD & back-feed protection
Mechanical dimensions
Under-board baseboard for Raspberry Pi 5, mounted underneath via M2.5 spacers. Off-the-shelf Pi 5 cases generally do not fit the assembled stack, so custom enclosures are expected for deployment. See Quickstart for the full assembly sequence.
Compliance
Regulatory and safety certification status for the Edge AI Expansion Board. Status reflects what has been confirmed by Sixfab R&D as of this revision.
CE, FCC, RoHS, and UKCA certifications, along with independent EMI/EMC test reports covering the PCIe interface, the internal USB hub, and the USB-C PD input, will be confirmed once formal compliance testing concludes.
Safety & handling
Always power off the Raspberry Pi 5 completely and disconnect the USB-C PD cable before installing, removing, or swapping M.2 modules, the PCIe FFC cable, or the USB Bridge PCBA. Hot insertion or removal can damage the DEEPX DX-M1, the NVMe SSD, the modem module, or the Pi 5 itself through current spikes on the PCIe and USB rails.
The minimum supported PSU is the Raspberry Pi 27 W USB-C PD Supply (5 V / 5 A). The 45 W supply is recommended whenever the AI accelerator, NVMe SSD, and LTE/5G modem are populated together. Standard 5 V / 3 A (15 W) phone chargers will trigger under-voltage warnings and may reboot the system. Also set usb_max_current_enable=1 in /boot/firmware/config.txt on first boot; without it, the Pi 5 pauses at boot and waits for a button press.
The 15 mm and 5 mm M2.5 spacers, the 4× M2.5 mounting screws, and the 3× M2 6 mm flat-head M.2 screws are all finger-tight only. Loose spacers cause intermittent pogo-pin contact, which surfaces as power glitches or reboots under inference load. Over-torquing strips the threads in the Pi 5 PCB and the threads are not field-repairable. No power driver.
Physical design notes
- No buttons or switches on the Expansion Board. No reset, no power button, no user-programmable switch. Power state follows the USB-C PD input.
- No back-feed protection on the Pi 5 USB-C side. Power must come from the Expansion Board only. Plugging a second PSU into the Pi 5's USB-C port causes only the Pi 5 itself to operate, and the Expansion Board stack is unsupported in that configuration.
- No power-monitoring circuitry. Real-time per-slot or full-stack power draw is not measurable from the Raspberry Pi side.
dxtopexposes NPU-side power only; full-stack power requires an external USB-C power meter. - ESD sensitivity. Handle the Expansion Board, the DX-M1 module, the NVMe SSD, and the LTE/5G modem by their edges. Avoid touching exposed M.2 contacts, pogo pins, or FFC pins without ESD grounding.
- No vibration qualification. The pogo-pin back-power connection has not been qualified for high-vibration environments (drones, mobile robots). Long-term reliability under sustained shock and vibration is unverified.
- Indoor commercial use. The Edge AI Expansion Board is a commercial-grade electronic assembly intended for indoor deployment. Outdoor use requires a sealed enclosure addressing moisture, temperature, ventilation, and airborne contaminants.
Updated 1 day ago