johnfulgor

Hello,
I'm implementing a simple protocol to communicate to a device via serial port.
My program should:
1)Write a packet
2)Wait till a timer is expired, or exactly N characters are read

In other words a complete packet should arrive within a certain time, or the read fails.

I've read about termios config (VMIN & VTIME), as well as about open system call flags, but I'm a bit confused and need some clarification.
Thanks!
John

matsp

VMIN and VTIME is a bit tricky to get right.

I think, if you have a set packet size, then you can set VMIN to the number of characters, and VTIME to the timeout value.

If you have a variable packet size, then you will need to use a different technique - the best way is to set it up so that you have a short timeout, and then use a different mechanism (such as a timer) to detect overall timeouts.

--
Mats

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