CODEWITHSUNDEEP
clinuxserial-portbyte
user2081328
user2081328

Reputation: 169

Can't read more than eight bytes from serial port

I'm working in c programming language under Linux, trying to create a communication application with serial port. The program is sending data to a serial port and reading received data from a microcontroller. The received data could reach any number of bytes between 10 and 64 but no more and no less. I use the following code to read and write data:

unsigned char send_bytes[] = { 0x1, 0x6, 0x2, 0xAA, 0x2, 0x3, 0xB8, 0x4 };

int w = write(fd, send_bytes, sizeof(send_bytes)); // send

char buffer[64];

int r = read(fd, buffer, sizeof(buffer)); //read data

My problem is that r never gets more than 8 bytes of data. Does anyone know why is this the case?

Thanks in advance.

Upvotes: 0

Views: 1647

Answers (1)

unwind
unwind

Reputation: 399803

Perhaps your operating system is only providing 8 bytes of serial port buffering, so it "favors" to deliver incoming data in chunks of 8 bytes.

Repeat the read for as long as it has data available. You can use select() for this on systems where it's available.

Also, since the other end is a microcontroller which might be slower than your workstation by a large margin, perhaps the data simply isn't available yet when you do the read(). That's another reason to try again, of course.

Upvotes: 1

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