EP-0216-NEW

Description

The 52Pi 2.5Gbps PCIe Network Adapter for Raspberry Pi 5 is a PCIe-based expansion card that adds a second, full-speed 2.5 GbE port to the Pi 5. A detachable PoE+ daughter-board (pluggable via on-board headers) turns the adapter into a fully IEEE 802.3at-compliant power source: it receives PoE+ over the new RJ45 jack and simultaneously delivers up to 25 W to the Raspberry Pi 5 through a USB-C plug, eliminating the need for a separate PSU. Data still travels at native PCIe speeds over a supplied FPC cable, while GPIO pass-through pins on the base board provide the auxiliary power rails required by the on-board NIC. The result is a single, compact module that combines high-speed networking and reliable PoE+ power in one stackable solution.

Features

High-speed networking: Realtek-based 2.5 Gbps Ethernet controller (100/1000/2.5 G auto-negotiation)
Native PCIe interface: Dedicated PCIe Gen 2 ×1 link to Raspberry Pi 5 via flexible FPC cable
Optional PoE+ module: Pluggable board adds IEEE 802.3at (PoE+) power input and USB-C 5 V / 5 A output to the Pi
Single-cable operation: Network data and power delivered through one RJ45 connection
GPIO pass-through: Base-board pins must mate with Pi GPIO header to supply on-board NIC with required power
Compact & stackable: Low-profile design keeps HAT footprint, leaves remaining GPIO pins accessible
Plug-and-play: Works out of the box with recent Raspberry Pi OS kernels; no external drivers needed
Real-time speed LEDs: Four labeled LEDs (100 M, 1 G, 2.5 G) indicate current link speed for quick diagnostics

Gallery

PCB outlook

===Function details===

===Product Dimension===

Hardware assembly

Package Includes

===Hardware assembly===

Power down the Pi 5.
Plug the 40-pin header of the 52Pi base board onto the Pi’s GPIO (this rail-powers the NIC).
Connect the supplied FPC ribbon between the adapter’s PCIe slot and the Pi’s PCIe FFC connector (labelled “PCIe” next to the DSI/CSI slots).
If you are using the PoE+ daughter-board, seat it on the two 4-pin headers.

– Plug a USB-C cable from the daughter-board’s USB-C PD OUT into the Pi 5’s USB-C power port. – Plug an 802.3at/af+ switch into the RJ45 on the daughter-board.

Power on the PoE switch; the Pi should boot automatically.

Verify PCIe enumeration

sudo lspci -nn | grep -i eth

You should see something like:

0001:01:00.0 Ethernet controller [0200]: Realtek Semiconductor Co., Ltd. RTL8125 2.5GbE Controller [10ec:8125] (rev 05)

If the device is missing, check that the FPC is fully seated and the GPIO header is firmly mated.

Kernel driver

Pi OS Bookworm ships with r8169/rtl8125 modules ≥ 9.010, so the adapter is recognised out-of-the-box. Update just in case:

sudo apt update && sudo apt full-upgrade -y
sudo reboot

Interface naming & link-speed LEDs

The new NIC appears as eth1 (Pi’s on-board is eth0). The four LEDs next to the RJ45 indicate negotiated speed in real time:

LED indicators: “100Mbps” = 100 Mbps, “1Gbps” = 1 Gbps, “2.5Gbps” = 2.5 Gbps.

Network configuration examples

DHCP

sudo nano /etc/dhcpcd.conf

Add at the bottom:

interface eth1
  dhcp

Save, then

sudo systemctl restart dhcpcd

Static IP

interface eth1
  static ip_address=192.168.10.2/24
  static routers=192.168.10.1
  static domain_name_servers=8.8.8.8

PS: Replace the IP address with your own network configure.

Checking with ethtool

ethtool -i eth1
ethtool -g eth1

If both commands report “Operation not supported”, the driver is hard-coded.

Ensure 2.5 GbE is actually negotiated

sudo ethtool eth1 | egrep 'Speed|Duplex|Auto-neg'

If you see Speed: 1000Mb/s but the switch supports 2.5 G, force it once:

sudo ethtool -s eth1 autoneg on advertise 0x8000000001028

(0x8000000001028 enables 2.5G advertisement for the RTL8125 PHY .) Make it permanent via systemd:

sudo systemctl edit --force --full set-eth1-2g5.service

add following parameters

[Unit]
Description=Force 2.5 GbE advertisement on eth1
After=network-pre.target
Before=network.target

[Service]
Type=oneshot
RemainAfterExit=yes
ExecStart=/sbin/ethtool -s eth1 autoneg on advertise 0x8000000001028

[Install]
WantedBy=multi-user.target

save it and enable the service.

sudo systemctl enable --now set-eth1-2g5.service

Performance tuning (optional)

# Increase MTU

sudo ip link set eth1 mtu 9000
# Enable GRO/GSO

sudo ethtool -K eth1 gro on gso on

PoE+ power confirmation

Open a terminal and typing following commands:

vcgencmd get_throttled

All bits 0 → power OK. If throttled=0x50000 (undervoltage), either the switch is not 802.3at capable or the cable is sub-standard.

Keywords

52Pi PCIe 2.5GbE PoE+ HAT, Raspberry Pi 5 network adapter, 2.5 Gbps PCIe NIC, PoE+ powered Pi, USB-C 25 W output, IEEE 802.3at injector, Link-speed, LEDs, GPIO pass-through, Single-cable networking, Realtek 2.5 GbE controller