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

docs/user.txt

@@ -878,10 +878,13 @@ Turn speech on or off:
   enabled=True
 Values: on=''True'', off=''False''
 
-# Select speech driver, options are speechdDriver (default), genericDriver or espeakDriver:
+# Select speech driver, options are speechdDriver (default), genericDriver, dectalkDriver, litetalkDriver, doubletalkDriver or tripletalkDriver:
 driver=speechdDriver
-#driver=espeakDriver
 #driver=genericDriver
+#driver=dectalkDriver
+#driver=litetalkDriver
+#driver=doubletalkDriver
+#driver=tripletalkDriver
 
 Select the driver used to generate speech output.
 
@@ -890,7 +893,10 @@ Select the driver used to generate speech output.
 Available Drivers:
   * ''genericDriver'' using the generic driver, for Fenrir <1.5 this is not available
   * ''speechdDriver'' using speech-dispatcher, for Fenrir <1.5 just use ''speechd''
-  * ''espeakDriver'' using the espeak directly, for Fenrir <1.5 just use ''espeak''
+  * ''dectalkDriver'' using DECtalk-compatible serial hardware or RPITalk
+  * ''litetalkDriver'' using LiteTalk-compatible serial hardware or RPITalk
+  * ''doubletalkDriver'' using DoubleTalk LT-compatible serial hardware
+  * ''tripletalkDriver'' using TripleTalk-compatible serial hardware
 
 The rate selects how fast Fenrir will speak. 
   rate=0.65
@@ -921,6 +927,18 @@ Select the language you want Fenrir to use.
   language=english-us
 Values: Text, see your TTS synths documentation what is available.
 
+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''