More attempts at getting this usb dectalk working.

docs/user.md

@@ -340,18 +340,24 @@ status formats, which change too frequently to support reliably.
 - **speechdDriver** - Speech-dispatcher (recommended)
 - **genericDriver** - Command-line TTS (espeak, etc.)
 - **dectalkDriver** - Serial DECtalk-compatible hardware speech
+- **dectalkUsbDriver** - Native Access Solutions DECtalk USB (`0dd0:2001`)
 - **litetalkDriver** - Serial LiteTalk-compatible hardware speech
 - **doubletalkDriver** - Serial DoubleTalk LT-compatible hardware speech
 - **tripletalkDriver** - Serial TripleTalk-compatible hardware speech
 
-For hardware speech, set `speech#hardware_device` to an explicit serial path.
+For serial hardware speech, set `speech#hardware_device` to an explicit path.
 RPITalk gadget mode usually appears as `/dev/ttyACM0`; USB serial adapters
 usually appear as `/dev/ttyUSB0`; built-in serial ports may be `/dev/ttyS0`.
 The default baud rate is `9600`. `doubletalkDriver` targets
 DoubleTalk LT-style serial devices, not the internal DoubleTalk PC ISA card.
-USB TripleTalk devices work only if Linux exposes them as a serial tty such as
-`/dev/ttyACM0` or `/dev/ttyUSB0`; USB-only models with no tty device need a
-separate driver.
+The `dectalkUsbDriver` autodetects the native Access Solutions DECtalk USB and
+ignores both serial settings. It requires PyUSB and a libusb backend. From a
+source checkout, install them with
+`python3 -m pip install '.[dectalk_usb]'`. A non-root Fenrir process also needs
+a local udev rule granting its account read/write access to USB ID
+`0dd0:2001`; do not make the device world-writable. USB TripleTalk devices work
+only if Linux exposes them as a serial tty such as `/dev/ttyACM0` or
+`/dev/ttyUSB0`.
 
 ### Sound Drivers  
 - **genericDriver** - Sox-based (default)