Hi Karen, I have checked the web regarding Dectalk USB:
https://www.tegakari.net/en/2017/10/dectalk_usb/ shows an image of a
small device indeed having both USB and serial port connectors, as well
as a 6 volt power connector. you can also run it for 1 hour from a 9
volt battery.
However, somebody on Linuxquestions.org complains about a 4 second delay
when using the device in RS232 mode with Linux a few years ago.
https://archive.org/details/dectalk-usb-user-manual
comes as a single text file, which mentions that RS232 mode is Dectalk
Express compatible, made by axsol access solutions, running Fonix
Dectalk on a Dragonball cpu with 16 mb of flash and 32 mb of ram. rs232
speed is not given, but USB speed is 12 mbps, so the manual recommends
to use USB.
You can find an open source version of the Dectalk engine on github now:
https://github.com/dectalk/dectalk
This probably allows you to use it for software speech output on Linux.
If you use any embedded controller with a serial, but no USB port built
in, you always have 2 choices to connect USB: Add a bridge chip to your
circuit or use an USB to serial cable which has the bridge chip built
into it.
Either way, a modern operating system will see an USB-based serial port
and then let apps use that just like a serial port, but with a wider
variety of speed choices. In DOS, you would first have to load an USB
and bridge driver before you can access that not-physically-RS232 port
at all. Running DOS in an emulator is another option, letting you use
the drivers of the host operating system instead of needing DOS drivers.
I would assume that quite a few software speech synths and screen
readers are available for Linux, but I do not know which of them are how
good.
Anyway, we now know that Dectalk USB can be switched to RS232 mode,
which lets you use it with actual RS232 ports. You can also use it in
RS232 mode with USB to serial cables if no physical RS232 port exists
ini the PC, or if you hope to improve transfer speed by using USB.
Both will offer some degree of Dectalk Express compatibility, which is
good in case the native USB mode of Dectalk USB differs too much from
what DOS Dectalk drivers expect.
Regards, Eric
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