Thanks Nikolaus. Using /dev/ttyUSB0, the code from your link also produces spurious communications, receiving some characters but not others.
I should point out my posted code was for illustration only. On Wednesday, 24 September 2014 14:34:03 UTC+1, Dr. H. Nikolaus Schaller wrote: > > > Am 24.09.2014 um 13:42 schrieb Julian Gold <[email protected] > <javascript:>>: > > So I have been trying to write code to read data asynchronously from a > serial port. I have tried it with /dev/ttyO1 (using UART1), and also with > /dev/ttyUSB0 (using an FTDI USB cable in the USB port). > > Here is a snippet of code. This fails on both serial ports, but in > different manners: > > > > void readSerial( int fd ) > { > fd_set readfs; > FD_ZERO( &readfs ); > FD_SET( fd, &readfs ); > while( 1 ) > { > select( fd+1, &readfs, 0, 0, 0 ); > if (FD_ISSET( fd, &readfs )) > { > char buffer[32]; > int n = read( fd, buffer, 32 ); > printf( buffer ); fflush( stdout ); > } > } > } > > > On /dev/ttyO1, the select() call blocks permanently, with no input being > acknowledged. On /dev/ttyUSB0, the function prints EVERY OTHER character, > so if I type "connect" into my PC terminal program, I will get either > "cnet" or "onc" depending on what came before. Either way, it appears > select() is broken because if I replace this with > > while((n= read(fd,buffer,32)) > 0) > { > printf(buffer); fflush(stdout); > } > > Then I get "connect" as expected on /dev/ttyUSB0 (untried as yet on > /dev/ttyO1). This seems like a fundamental problem with the Angstrom kernel? > > > No. With your program logic. You do not process the return value of the > read() system call which might be 1..32. > And, printf(buffer) is very dangerous. What would happen if you receive > the string "%s“? > > Try this code: > > > http://git.goldelico.com/?p=gta04-rootfs.git;a=blob;f=config/root/femtocom.c;h=7f15df363f384786fad084c1217d05d00a6746e3;hb=HEAD > > — hns > -- 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.
