Tool/software:
Dear experts
I used a TDA4VEN board, and when I use the select function to poll whether the current serial port is readable, it keeps returning -1.
code snap:
fd = open("/dev/ttyS2", O_RDWR | O_NONBLOCK);
ret = pthread_create(&uart_read_thread,NULL,uart_read_thread_fun,&data);
void *uart_read_thread_fun (void *data)
{
int ThreadFd = fd;
struct timeval WaitTime;
fd_set fds;
int ReadResult=0;
FD_ZERO(&fds);
FD_SET(ThreadFd,&fds);
WaitTime.tv_sec = 0;
WaitTime.tv_usec = 100000;
printf("in read thread\n");
while(1)
{
if(select(ThreadFd+1,&fds,0,0,&WaitTime) > 0)
{
ReadResult = read(ThreadFd,BufForRead,sizeof(BufForRead));
if(ReadResult > 0)
{
readCount++;
printf("data=%s,ret=%d,read count=%ld\n",BufForRead,ReadResult,readCount);
}
}
else
{
printf("read select error\n");
}
}
}
If don't use the select function and just read, it can read the data.
fd = open("/dev/ttyS2", O_RDWR);
ret = pthread_create(&uart_read_thread,NULL,uart_read_thread_fun,&data);
void *uart_read_thread_fun (void *data)
{
int ThreadFd = fd;
struct timeval WaitTime;
fd_set fds;
int ReadResult=0;
FD_ZERO(&fds);
FD_SET(ThreadFd,&fds);
WaitTime.tv_sec = 0;
WaitTime.tv_usec = 100000;
printf("in read thread\n");
while(1)
{
//if(select(ThreadFd+1,&fds,0,0,&WaitTime) > 0)
//{
ReadResult = read(ThreadFd,BufForRead,sizeof(BufForRead));
if(ReadResult > 0)
{
readCount++;
printf("data=%s,ret=%d,read count=%ld\n",BufForRead,ReadResult,readCount);
}
// }
//else
//{
// printf("read select error\n");
//}
}
}
So the UART port does not support non blocking access.
Is this because the kernel driver does not support it? Is there a way to make corrections.
sdk version:
ti-processor-sdk-linux-adas-j722s-evm-10_00_00_08-Linux-x86-Install.bin
Thanks.
