Re: [Ftdi-usb-sio-devel] 62 bytes... comes from where?

[Kentaro F. <fu...@is...>]

Hello,

Some addition to my previous mail.

Our code works well with FTDI's driver for Windows.

I have read the driver code and realized the meaning of 62 bytes.
I modified driver to dump some debug messages. We had got a lot of
TTY_OVERRUN when the baud rate was 700Kbps. I can't belive that
our machine is not fast enough to receive 700Kbps data (Pentium4 1.7GHz).

Here is a test code to receive data from usbserial.

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <fcntl.h>
#include <unistd.h>
#include <termios.h>
#include <errno.h>
#include <linux/serial.h>
#include <asm/ioctls.h>
#include <sys/time.h>

#define DATA_LENGTH 769
int fd;

int device_open(char *filename)
{
	struct termios tty;

	fd = open(filename, O_RDWR);
	if(fd < 0) return -1;

	tcgetattr(fd, &tty);
	tty.c_cflag = CS8|CREAD|CLOCAL|B38400;
	tty.c_iflag = IGNBRK;
	tty.c_oflag = 0;
	tty.c_lflag = 0;
	tty.c_line = 0;
	tty.c_cc[VTIME] = 0;
	tty.c_cc[VMIN] = 1;

	tcsetattr(fd, TCSAFLUSH, &tty);

	return 0;
}

int main(int argc, char **argv)
{
	struct serial_struct serinfo;
	unsigned char buf[800];
	int ret;
	int x, y, ymax;
	int p;
	struct timeval t1, t2;
	int total_byte = 0;
	int ttt;
	int i, j;

	if(argc != 2) {
		puts("missing device file name");
		exit(1);
	}
	if(device_open(argv[1])) {
		perror("failed to open device: ");
		exit(1);
	}

	serinfo.reserved_char[0] = 0;
	if(ioctl(fd, TIOCGSERIAL, &serinfo) < 0) {
		perror("failed to get serial info");
		exit(1);
	}
	printf("Baud_base: %d, divisor: %d\n",
			serinfo.baud_base, serinfo.custom_divisor);
	serinfo.custom_divisor=34;
	serinfo.flags |= ASYNC_SPD_CUST;
	if(ioctl(fd, TIOCSSERIAL, &serinfo) < 0) {
		perror("failed to set serial info");
		exit(1);
	}
	while(1) {
		gettimeofday(&t1, NULL);
		for(i=0; i<100; i++) {
			buf[0] = 0xff;
			ret = write(fd, buf, 1);
			if(ret != 1) {
				puts("w?");
			}
			total_byte = 0;
			while(total_byte < DATA_LENGTH) {
				ret = read(fd, buf, DATA_LENGTH-total_byte);
				printf("ret %d\n", ret);
				if(ret < 0) {
					if(errno != EAGAIN) {
						perror("");
					}
				} else {
					total_byte += ret;
				}
			}
		}
		gettimeofday(&t2, NULL);
		ttt = (t2.tv_sec - t1.tv_sec)*1000000 + t2.tv_usec - t1.tv_usec;
		printf("bps = %f\n", (float)DATA_LENGTH * 800 * 1000000/ ttt);
	}
	return 0;
}


Any suggestion are welcome.

Kentaro Fukuchi