serial port problems

[Larry Walker]

I am trying to read data from a "serial port" (using a USB-serial  
adaptor).

I am on a MacBook Pro running 10.5.8, using LiveCode 4.5, and Prolific  
model 2303 USB-serial adaptor.

The following code does not work:

on mouseUp
    put "modem:" into usbSerial
    put empty into field "Field"

    open driver usbSerial for text read
    read from driver usbSerial for 5 chars
    put it after field "field"

    close driver usbSerial
end mouseUp

Setting a breakpoint on the "read from" shows that the "open" does not  
appear to fail. Single-stepping through the read does not wait for any  
input from the connected terminal, it returns immediately. "It" is  
empty afterward.

By reading for N chars I believe I am side-stepping any line - 
terminator issues.

I have confirmed that the USB-serial adaptor and the terminal can talk  
to each other properly, using the command-line invocation: 'screen / 
dev/tty.usbserial'. I have confirmed that the serialControlString  
matches the terminal's settings.

This fail whether I use "open file" or "open driver".
This fails whether I use "modem" or "printer" as the device.

If I use /dev/tty.usbserial", the IDE hangs and I have to Force-Quit it.

I have tried using the SerialTest.rev stack (http://www.troz.net/rev/stacks/SerialTest.rev 
) as well: identical results.

I have read Phil Worthington's paper on serial communication (http://www.pdslabs.net/usb/rev-usb1.pdf 
); I believe I'm doing just as he suggests (except for the no-name  
adaptor I bought), but no luck. I did notice that "the DeviceNames"  
seems to now return its results in a format different from the one  
Phil describes, for whatever that might be worth (LC4.5 changes?).

Has anything changed in LC4.5 regarding serial communication? Can  
others run the serialTest.rev script properly under LC4.5?

Any suggestions welcome!


Larry Walker

Walker Energy Systems LLC
Madison, WI  USA

Strategies & Technologies

www.walkerenergysystems.com