Hi.
Thanks for the answer.
I tried "setserial /dev/ttyS1 low_latency" before launching my program,
but I didn't notice any difference.
I still have at least 20 ms latency before AND after transmission.
Is the syntax correct? Am I using the command correctly? Am I supposed
to add something to my program in order to benefit from the low latency ?
Regards,
Erwin Authried a écrit :
normally, there is a latency of ~5-10msec before characters are
processed. This can be reduced with setserial, with the low_latency
parameter.
The maximum of 250msec that you mentioned seems very slow, however. Have
you made sure that your serial driver uses interrupts, otherwise it may
fall back to polling.
-Erwin
Am Donnerstag, den 28.05.2009, 09:27 +0200 schrieb Emmanuel Viollet:
Hi.
I'm running uclinux 2.6.24.2-uc0 on an Olimex LPC2468 evaluation board
and have an issue with serial ports.
I'm using the standard Linux serial functions (open(), write(), etc.),
and have discovered (after analysis with an oscilloscope) that the delay
between the write() function and the actual ouput on the serial port
varies between 20 and 250 ms.
I find this delay quite long. Is there anything I can do to force the
serial output as soon as I've put the data in the output buffer?
Also, the tcdrain() function returns approx. 20ms AFTER the data has
finished being sent by the UART. Is there any way to reduce this delay?
In advance, thanks.
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