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serial port input control

Posted by TimT (TimT), 20 September 2004
Similar to the last posting -
I am setting up a serial port and sending data in a defined format to a device. The device responds in a defined format. But if the initial output format is wrong, there is no reponse or an undefined one.

Using the commands in the last posting:

set rsport [open /dev/ttyUSB0 w+]
fconfigure $rsport -blocking 1 -buffering none
set bytin [read $rsport 1]

it would lock in the last line if no input is received and an exit button would not be able to used to exit the program.
How can I check there is a input or not without having to read it?

Posted by admin (Graham Ellis), 21 September 2004
The -blocking 1 option that you have specified causes the channel to block while awaiting input. If you replace it by -blocking 0 then it will not block. You will then need to check the return from the read to see if you've got the one byte requested or nothing at all.

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