HR Display - Windows setup

Standalone ANT+ heart rate display for the second PC. Plugs into its own ANT+ dongle, pairs with the HR strap (wildcard - no pairing step needed), and shows a big BPM number full-screen in a browser on that PC's monitor.

1. Swap the USB driver (one-time, Zadig)

Windows will auto-attach its default driver to the ANT USB2 stick, which openant/libusb can't use. Fix once:

1. Plug in the second ANT+ dongle (not the one going to the Pi).
2. Download Zadig: https://zadig.akeo.ie/
3. Run Zadig, then in Options -> List All Devices, enable that view.
4. Select the ANT USB stick (0fcf:1008, usually shows as "Dynastream ANT USB Stick" or similar).
5. In the driver dropdown, choose libusb-win32 (or WinUSB).
6. Click Replace Driver / Install Driver.

If Device Manager later shows the stick under "libusb-win32 devices" (or "Universal Serial Bus devices" as WinUSB), the swap worked.

Note: the driver swap alone isn't enough - Windows still needs the actual libusb-1.0.dll runtime, which Zadig doesn't install. ant_rx.py handles this automatically via the libusb-package dependency below, so you shouldn't need to manually download or place any DLL yourself. If you still see usb.core.NoBackendError: No backend available after installing requirements, double check libusb-package installed correctly (see Troubleshooting below).

2. Install Python deps

From this folder in PowerShell:

python -m venv venv
venv\Scripts\activate
pip install -r requirements.txt

3. Run it

venv\Scripts\activate
uvicorn server:app --host 0.0.0.0 --port 8000

Then open http://localhost:8000 in a browser on this PC and go full-screen (F11). The page shows "searching for HR strap..." until it locks onto the strap, then switches to the live BPM number.

If the dongle isn't plugged in or the driver swap didn't take, the page will show "ANT+ dongle not found - retrying" and keep retrying every 5 seconds - no need to restart the server once you plug it in / fix the driver.

Files

• ant_rx.py - ANT+ HR receiver (openant), runs on a background thread
• server.py - FastAPI app: serves the page, bridges HR updates to connected browsers over WebSocket
• static/index.html - the display itself
• requirements.txt - Python deps

Troubleshooting

usb.core.NoBackendError: No backend available - this is different from "dongle not found." It means pyusb can't locate the libusb-1.0.dll runtime at all (Zadig only binds the driver, it doesn't install this). ant_rx.py patches pyusb to fall back to the DLL bundled by the libusb-package pip package, so this should be resolved automatically as long as pip install -r requirements.txt succeeded. If it still happens:

• Confirm libusb-package actually installed: pip show libusb-package
• Try pip install --force-reinstall libusb-package
• As a last resort, manually download libusb-1.0.dll (64-bit) from https://github.com/libusb/libusb/releases and copy it to C:\Windows\System32

ANT+ dongle not found - retrying (a DriverNotFound message, not NoBackendError) - this means the backend loaded fine but no ANT USB stick was detected at all. Check it's plugged in and Device Manager shows it under libusb-win32/WinUSB as described in step 1.

Notes

• Pairing is wildcard (device_id=0), so it locks onto whichever ANT+ HR strap it hears first. If you're ever running two straps near each other, that's worth knowing.
• The page dims the number and shows "signal lost" if no update has come in for 6 seconds - useful for telling a dropped/poor strap contact apart from a genuinely low reading.
• To run this automatically on boot, the simplest option is a shortcut to a .bat file (activate venv + run uvicorn) in the Windows Startup folder - happy to put that together if you want it to launch unattended.