Am 20.05.2015 um 10:35 schrieb [email protected]: > Thanks Nikolaus, tonight I will give it a try. > > But where do I place the echo? Without an echo to write some character there > is nothing to read. > > for ((x=0;x<100;x++)); do > echo -en '\xAA' > /dev/ttyO4 > read -n 1 -t 1 < /dev/ttyO4
remove the < /dev/ttyO4 here or you have it twice > done < /dev/ttyO4 > > Something like this? Just add the "< /dev/ttyO4" at the bottom to hold the > file descriptor open? you can also move the > /dev/ttyO4 to the end of the do. Basically this tells the shell to redirect for all commands inside the loop. > > Op maandag 18 mei 2015 17:18:00 UTC+2 schreef Dr. H. Nikolaus Schaller: > read </dev/ttyO4 opens the file and after the command is done it is closed. > The UART throws away characters received while the tty is closed. > > What you can do is > for … do > read > done </dev/ttyO4 > > Am 18.05.2015 um 15:18 schrieb [email protected]: > >> I have a problem with ttyO4. It looks like something is emptying the uarts >> buffer. >> >> When is run two bash scripts at the same time I can send characters and >> receive characters at the same time. The two files running parallel look >> like this (simplified): >> >> 1: >> for ((x=0;x<100;x++)); do >> echo -en '\xAA' > /dev/ttyO4 >> done >> >> 2: >> for ((x=0;x<100;x++)); do >> read -n 1 -t 1 < /dev/ttyO4 >> done >> >> Number 1 is sending and I receive the 0xAA at number 2. >> >> Now I try to combine these two files: >> >> for ((x=0;x<100;x++)); do >> echo -en '\xAA' > /dev/ttyO4 >> read -n 1 -t 1 < /dev/ttyO4 >> done >> >> This does not work. So I write one byte and I am to late to receive this >> byte. When I use the bash script reading parallel it works again. >> >> The 0xAA received at the RX, where does it go? Why isn't it in the >> Beaglebones (hardware) buffer? Is there some linux process reading these >> bytes before my own read (from the bash file) is ready to read? >> >> -- >> For more options, visit http://beagleboard.org/discuss >> --- >> You received this message because you are subscribed to the Google Groups >> "BeagleBoard" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to [email protected]. >> For more options, visit https://groups.google.com/d/optout. > -- For more options, visit http://beagleboard.org/discuss --- You received this message because you are subscribed to the Google Groups "BeagleBoard" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. For more options, visit https://groups.google.com/d/optout.
