[X4U] Problem with prolific2303 usbserial driver

[Stroller]

Hi again, Cheryl,

:D

On 6 Jul 2006, at 09:52, Cheryl Homiak wrote:

> I am trying to hook up a braille display to my mac mini using a  
> usbserial cable. The cable uses the prolific pl2303 driver and I  
> have the latest version;

I'm guessing you mean you're using something like this: http:// 
tinyurl.com/qlhre
?

> echo "I am very frustrated with usbserial" > /dev/cu.usbserial
> gets that repeated--this macine has speech as well as braille.  
> however, after that first response, unless I either reboot or  
> unplug the cable from the usb port and replug it, I get no further  
> responses. If I do unplug and replug the usb connector, I then get  
> another successful response--but only one.
> There is nothing defective in the serial cable or the usbserial  
> adaptor as they load and work perfectly and consistently on my  
> linux laptop.

I don't know that you're going to be TOO lucky here, I'm afraid. :(
Most of the discussion here is usually about getting printing working  
across a network and about PDFs & stuff like that. You *might* have  
more lucky on the x-unix at listserver.themacintoshguy.com list, but I'd  
hope the manufacturer (or Prolific) would be most responsive. After  
all, characters in & out is ENTIRELY what this product & chipset is  
about.

My only guess is that maybe OS X is adding some spurious character to  
the end of the data stream which the braille reader is unable to  
interpret. Is it possible to connect the usbserial cable to your Mac  
and its output to the serial port of a Linux box? And then read  
what's coming out the Mac & into the Linux box?

`echo "I am very frustrated with usbserial" > /dev/cu.usbserial`  
SHOULDN'T add any characters like this - it should be very simple. So  
I am kinda pulling at straws to think what's wrong. Could it be your  
terminal program? Have you tried writing a 3-line Bash script to do  
the same thing? If the terminal is the problem then a Bash script  
will run an truer environment & running it repeatedly should work.

Finally, try a different version of the driver. If a PPC driver will  
run under Rosetta then I might be inclined to give that a go. It is  
possible that a later driver has introduced a bug. Ideally Prolific's  
tech support will give you a debug version of the driver & get their  
coders involved - such a use of their products is critical to you,  
and a good company will recognise the value to their reputation of  
supporting their products in this way.

Stroller.