Hello

Description:
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in reference to another posting of mine "self written usb driver: received data is retransmitted", I discovered that received character are kept in a buffer. There may be a significant delay until a received character is actually dumped on the tty (around 100 characters)

Setup:
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I have 2 serial devices connected. On one of them, I am doing a 'cat /dev/ttySx'. On the other device, I am sending data via 'echo "12345" > /dev/ttyUSBy'. After sending bigger amounts of data to the receiving serial device (a couple of 100 characters) at once, I observe a buffering behavior, i.e. characters sent are not immediatly dump onto the receiving terminal. Instead data previously sent and not yet displayed is dumped.

Question:
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I wonder how I can tell the tty to flush all data in its receive buffer (preferable via stty) ?

Remark: I am logged in via ssh which means that I am working on pty. Not sure if that makes a difference.

Thanks
Tilman

Serial ports and devices have considerable underlying configuration that is obscured from ordinary shell commands. For this reason, I consider the shell to be a very clumsy vehicle for performing serial communications. Neverthless, stty implements a shell interface to the termios API to fine tune the behavior of the serial port. I suggest that you study the following online tomes:
Serial-Howto
Serial Programming Howto
Serial Programming Guide for POSIX OS's

From that, you should be able to divine that the VMIN & VTIME settings will probably address your read delay issues. In stty-speak, these seem to correspond to the 'min' and 'time' options.
I'm not sure how to reduce the buffering of output data. Perhaps simply using raw mode will suffice.

--- rod.