buzzrs

Phones as buzzers for the Buzz! quiz games on PS3 and RPCS3.

buzzrs shows a buzzer controller in the phone's browser (no app to install) and turns the presses into an emulated USB Buzz! dongle. The game sees a real "Logitech Buzz(tm) Controller V1" (054c:0002) with 4 wireless buzzers, red lights included.

• No hardware buzzers needed: every phone on the same Wi-Fi is one buzzer. Scan a QR code and you are in.
• Real USB device: works with the unmodified games on a real PS3, and in RPCS3 through USB passthrough.
• Up to 8 players: two dongles, for the Buzz! games that support a second set of buzzers.

Where it runs

buzzrs emulates the dongle with the device-mode side of USB, so the machine that runs it has to be able to act as a USB device:

Setup	Dongle made with	Plugged into	Players
Linux PC	dummy_hcd (a virtual USB cable inside the PC)	RPCS3 on the same PC	8
Linux board with a USB device port (Raspberry Pi Zero 2 W / 4 / 5, Radxa, Orange Pi…)	configfs HID gadget	PS3	4 per board
Rooted Android phone (Magisk)	FunctionFS (no custom kernel needed)	PS3 or a PC with RPCS3	4 per phone

Tested with RPCS3 on Linux and with a Samsung Galaxy J7 2017 (SM-J730F, Android 9, Magisk) plugged into a PS3.

Build

cargo build --release

For an Android phone, build one static binary. No NDK is needed, because .cargo/config.toml links with rust-lld:

rustup target add armv7-unknown-linux-musleabihf
cargo build --release --target armv7-unknown-linux-musleabihf   # 32-bit Android (uname -m: armv7l / armv8l)

rustup target add aarch64-unknown-linux-musl
cargo build --release --target aarch64-unknown-linux-musl       # 64-bit Android (aarch64)

Linux PC + RPCS3

Run target/release/buzzrs without arguments, for example by double-clicking it:

1. If the dongles are not set up yet, the system asks for your password once (pkexec) and buzzrs creates two of them through dummy_hcd.
2. The host page opens in the browser. It shows the QR code and address for the phones, the state of the dongles, every buzzer live (phone connected, buttons, lights) and a Quit button.
3. Start a Buzz! game and open the address on the phones (same Wi-Fi).

The same steps by hand:

sudo ./target/release/buzzrs gadget-up      # two dongles; --sets 1 for one
./target/release/buzzrs serve               # serve the phones (as your user)
sudo ./target/release/buzzrs gadget-down    # remove the dongles

gadget-up loads libcomposite, usb_f_hid and dummy_hcd, creates the gadgets, gives /dev/hidg* and the new USB devices to your user, and frees them from the kernel's HID driver. lsusb then lists 054c:0002 once per dongle.

Linux board + PS3

On a board with a USB device-mode port (Raspberry Pi: dtoverlay=dwc2 in config.txt, modules-load=dwc2 in cmdline.txt), run the same commands. gadget-up picks the board's real device controller instead of dummy_hcd. Plug the board's device port into the PS3; the phones connect to the board over Wi-Fi.

A board has one device port, so one board is one set (4 players).

Rooted Android phone + PS3

The phone itself becomes the dongle: plugged into the PS3 by its USB cable, it shows up as 054c:0002, and it also serves the controller page to the other phones.

1. Copy the static binary (see Build) into Termux's home directory.
2. In Termux:

   pkg install root-repo iw    # once: lets buzzrs turn off Wi-Fi power saving
   chmod +x buzzrs
   termux-wake-lock            # keeps Android from suspending Termux
   su -c ./buzzrs
   

   The host page opens on the phone; the players scan its QR code.
3. Plug the phone into the PS3 and start the game.
4. Stop with the Quit button or Ctrl+C. adb and MTP come back a few seconds later; a reboot also restores everything.

Older Android kernels (for example Samsung's 3.18) have no configfs HID function. buzzrs uses the FunctionFS instance that adbd normally owns (/dev/usb-ffs/adb): it stops adbd, describes a HID interface with the Buzz! report descriptor, switches the gadget to 054c:0002 and answers the host's requests itself. While it runs, adb over USB is not available.

To use the phone-dongle with RPCS3 on a Linux PC, allow your user to open it:

echo 'SUBSYSTEM=="usb", ATTR{idVendor}=="054c", ATTR{idProduct}=="0002", MODE="0666"' | sudo tee /etc/udev/rules.d/51-buzz.rules
sudo udevadm control --reload

Playing

• Controller page (http://<address>:8000/): each phone takes the first free buzzer and shows its number at the top. ?p=3 in the address asks for buzzer 3, and a refreshed page keeps its buzzer. Multi-touch works (hold one colour and press another). On a PC, Space is the buzzer and 1–4 are blue, orange, green and yellow.
• Host page (/host): the QR code, the dongles and every buzzer live.
• Test page (/test): all buzzers in one browser window, to try the game without phones.

With two dongles on one machine, buzzers 1–4 are the first set and 5–8 the second. With two separate dongles (for example a PC dongle and a phone-dongle, or two phones), each one runs its own server: start the second one with --set 2 (su -c "./buzzrs --set 2" on a phone) so its buzzers are numbered 5–8. The game decides which dongle is its first set, so if the numbers come out the other way round, swap the --set values.

Troubleshooting

RPCS3 does not see the buzzers. Check that Buzz emulated controller is set to Null. If the log shows libusb couldn't open USB device … errno=13, your user cannot open the USB device: for the PC dongles run gadget-up again, for a phone add the udev rule above.

RPCS3 sees only one of two dongles. RPCS3 tells USB devices apart by port and address only, not by bus, and every dummy_hcd bus puts its device on port 1, address 2. gadget-up detects the clash and plugs the second dongle in again until it gets another address.

Presses arrive late or get lost. This is phone Wi-Fi power saving: a dozing phone holds packets for up to about two seconds. On the dongle phone, buzzrs turns power saving off with iw and keeps it off. On the players' phones, the controller page sends a small packet every 250 ms to keep the Wi-Fi awake, and the ping shown in the corner is the median of the last ones. If a player's phone still lags, turn off its battery saver or Wi-Fi power saving mode.

The double-clicked app does not start. buzzrs uses port 8000, or the next free one if something else has it. Double-clicking while it runs just opens its page. Errors show as a desktop notification.

A phone-dongle disappears from the host. Samsung's kernel takes a USB bus suspend for an unplugged cable and switches the gadget off. buzzrs notices that the cable is still in and switches the dongle on again within a couple of seconds.

A phone lost adb. buzzrs gives USB back when it stops. If it was killed hard, reboot the phone.

How it works

The dongle (src/report.rs) has the same layout as RPCS3's usb_device_buzz:

• Input report (5 bytes, interrupt IN): two axes fixed at 0x7f, then 20 button bits. Buzzer i uses bits 5i … 5i+4, in the order red, yellow, green, orange, blue. The last 4 bits are vendor bits and are always set (0xf0).
• Output report (7 bytes, SET_REPORT on the control endpoint): bytes 1–4 are the four red lights.

The games refresh the lights by sending "all off" and, a few milliseconds later, the real state. buzzrs ignores an "off" that is followed by another report within 40 ms, so the lights on the phones do not flicker.

Backends:

• gadget (src/gadget.rs): Linux configfs with the hid function and no_out_endpoint.
• ffs (src/ffs.rs): Android FunctionFS. The control endpoint is polled instead of blocked on, because a blocking read on Samsung's 3.18 kernel sometimes misses the wake-up and the host's requests stall.
• none: only logs the reports, to try the pages.

Command line

buzzrs [--set N]                                 app mode: set up, serve, open the host page
sudo buzzrs gadget-up [--sets N] [--owner USER]  create N Linux gadget dongles (default 2)
sudo buzzrs gadget-down                          remove them
buzzrs serve [--port 8000] [--backend gadget|ffs|none] [--set N] [--open]

RUST_LOG=debug logs every light change and USB event.

License

MIT, see LICENSE.

Buzz! is a trademark of Sony Interactive Entertainment. This project is not affiliated with Sony or Logitech.