Hi. Thanks to the really good post on this forum I was able to write a script on Linux Shell for send and read data to a serial port.

But I’m facing a problem now. And I hope some one can give me a hand on this.

If by any mean I send to de device anything else than the predefined strings, stated by the manufacturer, the device ceases to respond. The only way I found its to turn off and then turn on the thing again. Which its very impractical.

Its there any way to "reset de UART chip on the device" or send some string based on the RS232 standard that clean the device buffer?

Not really but it depends on how the device operates on bad commands. Need more information on this device like make/model and its predefined strings.

It might be that all you need to do is send a carriage return character. Does your device use ASCII or binary commands? If your device uses ASCII commands you can try experimenting using minicom and see what happens.

Hi michaelk.
Finally a could resolve the problem. I read somewhere that sending a zero string cleans the buffer on the UART chip. According to the web site this its a standard of the RS232 protocol.

After several tries I discover that sending a string whit zero, in hexadecimal format, twice deletes the buffer and allow me to send more commands.

echo -e -n "\x00" > /dev/ttyS0
echo -e -n "\x00" > /dev/ttyS0

What i never understand its why do I need to send Two strings. But it works, so I'm not going to question it(too much jeje).