New hardware synth support added. Untested, so consider this experimental.

docs/fenrir.adoc

@@ -1548,8 +1548,12 @@ enabled=True
 Values: on=`+True+`, off=`+False+`
 
 # Select speech driver, options are speechdDriver (default),
-genericDriver or espeakDriver: driver=speechdDriver #driver=espeakDriver
+genericDriver, dectalkDriver, litetalkDriver, doubletalkDriver or tripletalkDriver: driver=speechdDriver
 #driver=genericDriver
+#driver=dectalkDriver
+#driver=litetalkDriver
+#driver=doubletalkDriver
+#driver=tripletalkDriver
 
 This Selects the driver used to generate speech output.
 
@@ -1677,6 +1681,29 @@ the pico module:
 language=de-DE
 ....
 
+Hardware speech drivers use a serial device. The default `+auto+` checks
+`+/dev/ttyACM*+` first, then `+/dev/ttyUSB*+`. Set an explicit path for
+stable systems.
+
+....
+hardware_device=auto
+hardware_device=/dev/ttyACM0
+hardware_device=/dev/ttyUSB0
+hardware_device=/dev/ttyS0
+....
+
+Hardware speech drivers use 9600 baud by default.
+
+....
+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.
+
 Read new text as it occurs auto_read_incoming=True Values: on=`+True+`,
 off=`+False+`