ArtNetDMX — Pico W Art-Net → Dual DMX

Firmware for Raspberry Pi Pico W that receives Art-Net over Wi‑Fi and outputs two DMX512 universes through RS‑485, using PIO + DMA at 40 Hz. A web UI configures Wi‑Fi (STA / AP) and shows / sets all 512 channels per universe.

Hardware

Signal	Pico W	RS‑485 module
DMX A data	GP0	DI (universe A)
DMX B data	GP1	DI (universe B)
GND	GND	GND
Power	3V3 or 5V	VCC (many MAX485 boards want 5V)

TX‑only: tie DE and /RE high (to VCC) on each module. XLR pinout is typically 1=GND, 2=Data− (B), 3=Data+ (A) — match your module labels.

Pins are defined in include/board.h.

Pico W GP0 ──► MAX485 A DI
Pico W GP1 ──► MAX485 B DI
Pico W GND ──► both module GND
VCC     ──► both module VCC
DE,/RE ──► VCC (TX enable)
A/B    ──► XLR / DMX cable

Build

Requires Pico SDK and an ARM GCC toolchain.

export PICO_SDK_PATH=/path/to/pico-sdk
mkdir -p build && cd build
cmake -DPICO_BOARD=pico_w ..
make -j$(nproc)

Flash with BOOTSEL + drag-and-drop, or:

picotool load -f build/artnetdmx.uf2

USB serial (115200) prints boot status, Wi‑Fi mode, and IP addresses.

Do not cp the UF2 onto a path that is not the mounted RPI-RP2 volume (a failed copy can leave a plain file instead of flashing).

First boot (AP)

1. Join Wi‑Fi ArtNetDMX / password artnetdmx
2. Open http://192.168.4.1/ (or http://artnetdmx.local/ once mDNS is up)
3. WiFi page: choose mode, credentials, Art‑Net universe numbers, mDNS hostname
4. Save — device reboots

Wi‑Fi modes

Mode	Behaviour
Access Point	SoftAP only (default ArtNetDMX / artnetdmx @ 192.168.4.1)
Station	Joins your LAN only. If join fails, SoftAP starts for recovery

There is no concurrent AP+STA mode (legacy “AP+Station” configs are treated as Station). SoftAP is paused while STA obtains DHCP, then left off if join succeeds.

mDNS hostname defaults to artnetdmx → http://artnetdmx.local/ (configurable on the WiFi page).

Art-Net

• UDP port 6454
• Replies to ArtPoll / sends ArtPollReply (QLC+ and similar discovery)
• Maps configured universes to physical ports A (GP0) and B (GP1)
• Defaults: universe 0 → A, universe 1 → B

SoftAP vs Station (important)

Mode	Art-Net transport
SoftAP	Controller joins the Pico’s AP. Broadcast ArtDmx usually works.
Station	Pico and controller share a home/office AP. Many APs drop Wi‑Fi broadcast, so ArtDmx broadcast never arrives. Use unicast to the Pico’s STA IP.

Unicast ArtDmx on STA has been verified end-to-end; subnet broadcast often is not delivered by the upstream AP.

QLC+ setup

1. Put the Pico in Station mode and note its IP (web UI, serial, or mDNS).
2. Inputs/Outputs → Art-Net plugin.
3. You will typically see two nodes: QLC+ itself and ArtNetDMX. Select ArtNetDMX (not the QLC+ loopback node).
4. Set output to unicast → Pico STA IP (e.g. 10.1.1.190), not broadcast and not 192.168.4.1 unless you are on SoftAP.
5. Enable the Art-Net output line (icon lit).
6. Map universes: 0 → DMX A, 1 → DMX B (or match the WiFi page).
7. Patch fixtures to those universes.

Confirm on http://<pico-ip>/ (Channels): Art-Net packet count should rise and channel values should follow faders. If the web UI updates but fixtures do not, check RS‑485 wiring / DE·/RE / cabling.

Web UI

• Channels — tabs for universe A/B; all 512 values; edit live; Clear / All 255
• WiFi — AP or Station, credentials, Art‑Net universes, mDNS hostname, live debug line
• Status strip: mode, IP, Art‑Net packet count, age since last packet per port

Manual channel edits drive the same buffers as Art‑Net; new Art‑Net packets overwrite those channels.

Embedded pages live in src/http_server.c. The www/ tree is a reference copy of the HTML structure.

Project layout

Path	Role
src/main.c	Boot, DMX timer, poll loops
src/wifi_mgr.c	SoftAP / STA, DHCP, mDNS hooks
src/artnet.c	ArtDmx + ArtPoll/ArtPollReply
src/dmx_out.c + .pio	PIO + DMA DMX TX
src/http_server.c	Web UI + JSON API
src/config.c	Flash config (CRC, versioned)
lwipopts.h	lwIP tuning (UDP PCBs, SoftAP DHCP, broadcast)

License notes

DMX PIO timing is adapted from jostlowe/Pico-DMX (BSD‑3‑Clause). DHCP server is from MicroPython / pico‑examples (MIT).