More attempts at getting this usb dectalk working.

docs/fenrir.adoc

@@ -1551,9 +1551,11 @@ enabled=True
 Values: on=`+True+`, off=`+False+`
 
 # Select speech driver, options are speechdDriver (default),
-genericDriver, dectalkDriver, litetalkDriver, doubletalkDriver or tripletalkDriver: driver=speechdDriver
+genericDriver, dectalkDriver, dectalkUsbDriver, litetalkDriver,
+doubletalkDriver or tripletalkDriver: driver=speechdDriver
 #driver=genericDriver
 #driver=dectalkDriver
+#driver=dectalkUsbDriver
 #driver=litetalkDriver
 #driver=doubletalkDriver
 #driver=tripletalkDriver
@@ -1684,7 +1686,7 @@ the pico module:
 language=de-DE
 ....
 
-Hardware speech drivers use a serial device. Set an explicit path.
+Serial hardware speech drivers use a serial device. Set an explicit path.
 
 ....
 hardware_device=/dev/ttyACM0
@@ -1700,9 +1702,14 @@ hardware_baud_rate=9600
 
 The `+doubletalkDriver+` targets DoubleTalk LT-style serial devices. It does
 not support the internal DoubleTalk PC ISA card.
-USB hardware speech synthesizers are supported only when Linux exposes them as
-a serial tty such as `+/dev/ttyACM0+` or `+/dev/ttyUSB0+`. USB-only TripleTalk
-models with no tty device need a separate driver.
+The `+dectalkUsbDriver+` autodetects the native Access Solutions DECtalk USB,
+USB ID `+0dd0:2001+`. It requires PyUSB and a libusb backend and ignores the
+serial device and baud-rate settings. From a source checkout, install the USB
+dependencies with `+python3 -m pip install '.[dectalk_usb]'+`. A non-root
+Fenrir process needs a local udev rule granting its account read/write access
+to `+0dd0:2001+`; do not make the device world-writable. Other USB hardware
+speech synthesizers are supported only when Linux exposes them as a serial tty
+such as `+/dev/ttyACM0+` or `+/dev/ttyUSB0+`.
 
 Read new text as it occurs auto_read_incoming=True Values: on=`+True+`,
 off=`+False+`