Hi Karl, Thanks for suggestion.
My problem in the code seems to be more specific to pthread, because if I have the read( ) in a while loop, then the UART receive is running normally. Data arrived at the receive buffer are able to be pick up. However, the problem begin when I create UART Rx thread that just continuously reading the UART buffer. Regina On Wednesday, July 20, 2016 at 3:21:44 PM UTC+8, Karl Karpfen wrote: > > Serial interface initialisation on Linux systems is a mess and it is easy > to forget something. That's why I would recommend to use a library which > does all the work for you like liboapc from > https://sourceforge.net/p/oapc/code/ci/master/tree/liboapc/ > > Am Mittwoch, 20. Juli 2016 08:56:50 UTC+2 schrieb Regina Choi: >> >> >> Hi, >> >> I have programmed (in C) UART4 read in thread with blocking read, the >> code as below: I confirmed that the UART receive port does have data >> through oscilloscope, but somehow there is no data in read( ), the return >> count always zero ? >> >> The strange thing is if minicom is open on the Uart4, then the read( ) in >> receive thread started to run as normal. However, the regular file write >> become weird. The string won't be able to be written into file ?! >> >> Btw, my BBB version is 3.8.13-bone47 >> >> >> #include<stdio.h> >> #include<stdlib.h> // required for fopen, exit() >> #include<fcntl.h> >> #include<termios.h> >> //#include<string.h> >> #include<unistd.h> >> #include<pthread.h> >> #include "readerComm.h" >> >> >> pthread_t uartRxT , uartTxT; >> int file, file2; >> >> int main (int argc, char* argv[]) >> { >> int count; >> >> pthread_attr_t attr; >> void *status; >> FILE *fdata; >> >> >> if(argc != 2) >> { >> >> printf("Invalid number of arguments, exiting!"); >> return -2; >> >> } >> >> if((file = open("/dev/ttyO4", O_RDWR | O_NOCTTY | O_NDELAY ))< 0) >> { >> perror("UART: Failed to open the file"); >> return -1; >> } >> >> fcntl(file, F_SETFL, 0); // blocking read >> struct termios options; //oriopt >> tcgetattr(file, &options); >> options.c_cflag = B9600 | CS8 | CREAD | CLOCAL; >> options.c_iflag = IGNPAR | ICRNL; >> >> options.c_iflag &= ~IGNBRK; >> options.c_iflag &= ~(IXON | IXOFF | IXANY); // shut off xon/xoff ctrl >> >> options.c_cc[VMIN] = 2; // Non Canonical input mode (as we didnt >> set ICANON for c_lflag) >> options.c_cc[VTIME] = 10; // 1 sec timeout >> >> >> tcflush(file, TCIFLUSH); >> >> tcsetattr(file, TCSANOW, &options); >> >> >> unsigned char cmd[] = {0x11, 0x00, 0x32}; //"Tx From Beaglebone "; >> >> if ((count = write(file, (char*)cmd, 3))<0){ >> perror("Failed to write to the output\n"); >> return -1; >> }else{ >> printf("Byte sent: %d \n", count); >> } >> >> fdata = fopen("capture.dat", "w"); >> if (fdata == NULL) { >> printf("I couldn't open capture.dat for writing.\n"); >> exit(0); >> } >> >> // save in file ( cannot print to file ??) >> fprintf(fdata, "%s", "test"); >> perror("UART: Test comment"); >> >> >> pthread_attr_init(&attr); >> pthread_attr_setdetachstate(& >> attr, PTHREAD_CREATE_JOINABLE); >> >> // Create UArt Tx thread >> if(pthread_create(&uartTxT, &attr, &uartTxWait, NULL)){ >> perror("GPIO: Failed to create the tx thread"); >> >> return -1; >> } >> >> // Create Uart Rx thread >> if(pthread_create(&uartRxT, &attr, &uartRxWait, NULL)){ >> perror("GPIO: Failed to create the rx thread"); >> >> return -1; >> } >> >> pthread_attr_destroy(&attr); >> pthread_join(uartRxT,&status); >> pthread_join(uartTxT,&status); >> >> close(file); // close first file descriptor >> >> // capture.dat file close >> fclose(fdata); >> >> return 0; >> >> } >> >> // UART RX thread >> void* uartRxWait(void *param){ >> >> unsigned char receive[100]; >> int count, n; >> fd_set input; >> struct timeval timeout; >> >> //initialize input set >> FD_ZERO(&input); >> FD_SET(file, &input); >> >> timeout.tv_sec=0; >> timeout.tv_usec=0; >> >> while(1){ >> >> if ((count = read(file, (void *)receive, 100))<0) >> { >> perror("Failed to read from input \n"); >> printf("count = %d\n", count); >> }else{ >> >> if(receive[2]==0x32){ >> printf("Header received \n"); >> } >> printf("Byte received [%d] \n", count); >> printf("Value of Pi = 0x%.2x\n", receive[0]); >> >> } >> >> } >> >> pthread_exit(0); >> } >> >> >> void* uartTxWait(void *param){ >> >> usleep(1000000); >> pthread_exit(0); >> } >> > -- 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 beagleboard+unsubscr...@googlegroups.com. To view this discussion on the web visit https://groups.google.com/d/msgid/beagleboard/25f8dbc3-6b82-4ce0-8c2e-2c8fa4666710%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
