GitHub - mattdeeds/pico-10base-t-rs: Bit-banged 10BASE-T Ethernet + Wi-Fi router in Rust on the Raspberry Pi Pico 2 W

Software 10BASE-T Ethernet (PIO bit-bang TX and RX) and wireless router on the Raspberry Pi Pico 2 W. Uses the dual Hazard3 RISC-V cores with pure Rust (no_std). A ~$5 micro talks 10 Mbit Ethernet to a real network with PIO, DMA, a RS-485 transceiver, and magnetics.

Rust port of C project, which extended kingyoPiyo/Pico-10BASE-T (the original C/PIO Manchester TX-only design) with a RX path — Manchester decode over an RS-485 transceiver. This Rust rewrite runs on rp235x-hal, exposes the NIC as a smoltcp phy::Device, then grows into a NAPT router with a cyw43 Wi-Fi AP.

Two builds

The build features give you either layer with no code changes:

• A standalone software 10BASE-T NIC (default build): the bit-bang PHY + smoltcp. A static-IP host that does ARP / ICMP / UDP / a tiny HTTP server.
• A wireless router (--features router): the same 10BASE-T as the WAN, a cyw43 2.4 GHz AP as the LAN, with L3 forwarding + NAPT between them, a DHCP server, and a status page.

What to expect (performance)

Full detail + method in docs/performance.md. Headlines (measured on real hardware):

It's a fun software-PHY NIC and a working router, not a fast router. The bit-bang TX is near line rate; RX bulk runs ~310 KB/s (the long-suspected "decode/PHY ceiling" turned out to be a fixable DMA-starvation bug — see docs/rx-bulk-ceiling.md §10). Latency is great; ideal for low-rate / IoT-scale traffic.

Hardware

• Raspberry Pi Pico 2 W (RP2350). The plain 10BASE-T NIC build also runs on a non-W Pico 2; the Wi-Fi/router builds need the W (cyw43).
• External 10BASE-T front end: an ISL3177E transceiver + HR911105A RJ45 magnetics. KiCad board design + gerbers/BOM are in hardware/.

Toolchain

• Rust ≥ 1.82, target riscv32imac-unknown-none-elf (rustup target add riscv32imac-unknown-none-elf).
• Flashing: picotool (USB), or OpenOCD over SWD: openocd -f interface/cmsis-dap.cfg -f target/rp2350-riscv.cfg -c "program <elf> verify reset exit".

Build & flash

# Standalone 10BASE-T NIC (static IP 192.168.37.24) — the default build
cargo build --release
cargo run   --release            # flashes via the .cargo/config.toml runner

# Other variants
cargo build --release --features wan-dhcp    # NIC as a DHCP client (WAN-style)
cargo build --release --features wireless    # cyw43 AP only (no wired side)
cargo build --release --features router      # WAN(10BT) + LAN(Wi-Fi) + NAPT router

The device logs status over USB CDC (assert DTR to read it): [R2b] heartbeat, [Rx] decode stats, and on the router build [Cyw43] / [Wan] / [Fwd] / [Nat] / [Perf] lines.

Wired host setup (10BASE-T peer)

The device emits Normal Link Pulses only (no auto-negotiation), so force the peer NIC to 10 Mbit half-duplex:

sudo ethtool -s <iface> speed 10 duplex half autoneg off
sudo ip addr add 192.168.37.19/24 dev <iface>

Router credentials

The cyw43 AP SSID/passphrase are compile-time placeholders in src/wireless.rs (AP_SSID / AP_PASSPHRASE = "change-me-please"). They should be changed.

How it works

• PIO0 drives the 10BASE-T PHY: SM0 = 20 MHz Manchester TX (256-entry lookup table → single-ended on GP14), SM1 = 60 MHz RX sampler (in pins, 1, 3 samples/half-bit), SM2 = a carrier-detect SM for the half-duplex CSMA/CA TX gate.
• DMA ferries the RX sampler into a double-buffer; core 1 owns the DMA_IRQ_0 handler running an edge-tracking DPLL Manchester decoder + FCS (re-anchors to each mid-bit transition to cancel clock drift).
• core 0 runs smoltcp (the control plane) and, on the router build, an embassy executor hosting the cyw43 Runner, the LAN/WAN net tasks, and the custom L3 forwarding + NAPT data path. PIO1 is a custom gSPI transport to the cyw43 radio.
• An RP2350 hardware watchdog auto-reboots + recovers the device if the loop ever wedges (a known intermittent hang under sustained full-MTU inbound).

Repo layout

The package is a library + a binary: the transport core is a reusable library crate that other projects can take as a Cargo dependency (e.g. pico-remote-probe, a network-attached SWD debug probe, uses it as its NIC); the router application in src/main.rs is the in-tree consumer.

• src/lib.rs — the library: eth_tx, eth_rx, eth_rx_dpll, eth_mac, manchester, crc (the 10BASE-T bit-bang NIC, PHY + MAC), plus multicore_riscv (Hazard3 core-1 launch), pico_reset (picotool USB reset), pio_util, and — behind the cyw43-phy feature — cyw43_phy (a smoltcp phy::Device over the cyw43 radio, no executor required).
• src/main.rs, src/wireless.rs, src/forward.rs, src/conntrack.rs, src/dhcp_server.rs, src/wan.rs — the router (cyw43 + forwarding + NAPT).
• docs/ — a thorough engineering log (how this was built + characterized). Start with docs/README.md.
• tools/ — host-side measurement scripts.

Limitations

Half-duplex (by MAC policy; the transceiver is FD-capable but FD only helps contended traffic); no auto-negotiation; RX bulk ~310 KB/s (next bounds: decode CPU time and the DMA half-fill ACK-latency floor — see docs/rx-bulk-ceiling.md §10). A hardware watchdog guards against hangs (the old full-MTU-inbound wedge stopped reproducing after the 2026-06 RX restructure, but the watchdog stays). Just an educational project, please don't replace your home router with this.

Credits

• kingyoPiyo/Pico-10BASE-T — the original C/PIO 10BASE-T TX design (MIT, Copyright © 2022 kingyo). This project is a Rust port of the author's own C project, which extended kingyoPiyo's work with the RX path (Manchester decode over an RS-485 transceiver).
• Niccle — a reference for the Manchester RX decode approach and circuit design.
• embassy cyw43 driver + firmware blobs (Infineon permissive binary license — see cyw43-firmware/).
• smoltcp, rp235x-hal.

License

Dual-licensed under either MIT (LICENSE-MIT) or Apache-2.0 (LICENSE-APACHE), at your option. The cyw43 firmware blobs in cyw43-firmware/ carry their own (Infineon) permissive license.