Pico W firmware creates driverless USB WiFi bridge (Layer-2)

pico-usb-wifi is an open-source firmware project that converts the Raspberry Pi Pico W into a driverless USB WiFi adapter that works with Windows, Linux, macOS, and other operating systems with USB CDC-NCM support. The Infineon CYW43439 chip found in the SBC can’t be used directly as a USB to WiFi bridge, and instead, the firmware implements a transparent Layer-2 bridge between the Pico W’s wireless module and USB interfaces. It basically works as an Ethernet to WiFi gateway/bridge, which exposes an Ethernet connection through USB (aka USB gadget mode) used to route Wi-Fi packets from the network.

pico-usb-wifi highlights:

• Transparent Layer-2 Bridging between the Pico W’s wireless and USB interfaces
• Exposed as a USB CDC-NCM device
• IPv4 and IPv6 with no NAT, no private subnet, and no port-forwarding to configure
• Out-of-band management and debug consoles over CDC-ACM serial
• WPA2-PSK and WPA3-SAE authentication (and open networks)
• Throughput - Average 4.75 Mbits/sec; mostly limited by the 12 Mbps USB 1.1 interface

Considering a low-end WiFi USB dongle costs $2-$3 and up, and the limited performance of the solution, it’s mostly useful for an emergency when you need WiFi connectivity and have a spare Raspberry Pi Pico W lying around. I don’t think it’s possible to significantly improve the performance over the native USB port, but as noted by the developer (白一百, baiyibai), leveraging the programmable I/Os on the RP2040 might be an option, and the Pico-100BASE-TX project might be a starting point.

Management Console

WiFi credentials and other parameters can be configured through the management console:

picocom /dev/ttyACM0
-- pico-usb-wifi v1.1.0 --
profiles: 0 saved (active: none)
ssid: (unset)
pass: unset
country: (unset)
debug: off
status: associating
host IPv4: (not seen yet)
(set|scan|list|use|save) # scan
[*] scanning...
networks (3):
1 MyNetwork -47 dBm a4:b1:c2:d3:e4:f5
2 CoffeeShop -68 dBm 00:11:22:33:44:55
3 Neighbour -81 dBm 9c:65:ee:ef:27:c7
(back|join|scan|live) # join 1
[*] staged -- set pass then save ...
profiles: 1 saved (active: 1)
ssid: MyNetwork
pass: unset
...
(set|scan|list|use|save) # set pass hunter2
[*] applying -- re-associating ...
(set|scan|list|use|save) # save
[*] saved to flash

Besides the /dev/ttyACM0 management port, the /dev/ttyACM1 port is used for debugging.

While designed for the Pico W board, it might also work for the Pico 2 W by compiling for the latter (TBC). The project has been designed with Claude Code (around one million tokens used), and the source code (C, based on the PicoSDK), explanations on how it all works, and instructions to build the firmware from source can be found on GitLab. Alternatively, you can download and install the pico-usb-wifi.uf2 binary directly on your board.

Via Adafruit

Jean-Luc started CNX Software in 2010 as a part-time endeavor, before quitting his job as a software engineering manager, and starting to write daily news, and reviews full time later in 2011.

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