问题描述
我正在尝试在 FPGA 板上读写数据.该板本身带有一个驱动程序,该驱动程序在插入该板时创建一个名为 ttyUSB0 的终端设备.在 FPGA 上,实现了异步接收器和发送器,它们似乎可以工作.
I'm attempting to read and write data from and to an FPGA board. The board itself came with a driver that create a terminal device called ttyUSB0 whenever the board is plugged in. On the FPGA, an asynchronous receiver and transmitter were implemented, and they seem to work.
但是,C 方面似乎存在问题.我一直在使用一些测试向量来测试 FPGA 是否输出了正确的信息.我注意到了一些事情:
However, there seems to be an issue on C side of things. I've been using some test vectors to test if the FPGA is outputting the proper information. I've noticed a few things things:
- 设备有时无法正确打开
- 有时无法检索或设置终端属性.
- 读取有时是非阻塞的,不会检索到正确的值.
以下是我如何设置终端和文件描述符选项.大部分内容来自这里:http://slackware.osuosl.org/slackware-3.3/docs/mini/串口编程
Below is how I set up terminal and file descriptor options. Much of it was taken from here: http://slackware.osuosl.org/slackware-3.3/docs/mini/Serial-Port-Programming
任何关于程序失败原因的建议或评论都会非常有帮助.
Any advice or comments as to why the program may be failing would be greatly helpful.
#include <stdio.h> // Standard input/output definitions
#include <string.h> // String function definitions
#include <unistd.h> // UNIX standard function definitions
#include <fcntl.h> // File control definitions
#include <errno.h> // Error number definitions
#include <termios.h> // POSIX terminal control definitions
int open_port(void){
int fd; // File descriptor for the port
fd = open("/dev/ttyUSB0", O_RDWR | O_NOCTTY);
if (fd == -1){
fprintf(stderr, "open_port: Unable to open /dev/ttyUSB0 %s
",strerror(errno));
exit(EXIT_FAILURE);
}
return (fd);
}
int main(void){
int fd = 0; // File descriptor
struct termios options; // Terminal options
fd = open_port(); // Open tty device for RD and WR
fcntl(fd, F_SETFL); // Configure port reading
tcgetattr(fd, &options); // Get the current options for the port
cfsetispeed(&options, B230400); // Set the baud rates to 230400
cfsetospeed(&options, B230400);
options.c_cflag |= (CLOCAL | CREAD); // Enable the receiver and set local mode
options.c_cflag &= ~PARENB; // No parity bit
options.c_cflag &= ~CSTOPB; // 1 stop bit
options.c_cflag &= ~CSIZE; // Mask data size
options.c_cflag |= CS8; // Select 8 data bits
options.c_cflag &= ~CRTSCTS; // Disable hardware flow control
// Enable data to be processed as raw input
options.c_lflag &= ~(ICANON | ECHO | ISIG);
// Set the new attributes
tcsetattr(fd, TCSANOW, &options);
////////////////////////////////////
// Simple read and write code here//
////////////////////////////////////
// Close file descriptor & exit
close(fd)
return EXIT_SUCCESS
}
更新我已经根据第一个答案修改了我的代码.这就是我现在拥有的:
UPDATEI've modified my code based on the first answer. This is what I have now:
#include <errno.h> // Error number definitions
#include <stdint.h> // C99 fixed data types
#include <stdio.h> // Standard input/output definitions
#include <stdlib.h> // C standard library
#include <string.h> // String function definitions
#include <unistd.h> // UNIX standard function definitions
#include <fcntl.h> // File control definitions
#include <termios.h> // POSIX terminal control definitions
// Open usb-serial port for reading & writing
int open_port(void){
int fd; // File descriptor for the port
fd = open("/dev/ttyUSB0", O_RDWR | O_NOCTTY);
if (fd == -1){
fprintf(stderr, "open_port: Unable to open /dev/ttyUSB0 %s
",strerror(errno));
exit(EXIT_FAILURE);
}
return fd;
}
int main(void){
int fd = 0; // File descriptor
struct termios options; // Terminal options
int rc; // Return value
fd = open_port(); // Open tty device for RD and WR
// Get the current options for the port
if((rc = tcgetattr(fd, &options)) < 0){
fprintf(stderr, "failed to get attr: %d, %s
", fd, strerror(errno));
exit(EXIT_FAILURE);
}
// Set the baud rates to 230400
cfsetispeed(&options, B230400);
// Set the baud rates to 230400
cfsetospeed(&options, B230400);
cfmakeraw(&options);
options.c_cflag |= (CLOCAL | CREAD); // Enable the receiver and set local mode
options.c_cflag &= ~CSTOPB; // 1 stop bit
options.c_cflag &= ~CRTSCTS; // Disable hardware flow control
options.c_cc[VMIN] = 1;
options.c_cc[VTIME] = 2;
// Set the new attributes
if((rc = tcsetattr(fd, TCSANOW, &options)) < 0){
fprintf(stderr, "failed to set attr: %d, %s
", fd, strerror(errno));
exit(EXIT_FAILURE);
}
////////////////////////////////
// Simple Read/Write Code Here//
////////////////////////////////
// Close file descriptor & exit
close(fd);
return EXIT_SUCCESS;
}
澄清一下,接收器和发送器使用 8 个数据位,1 个停止位,并且没有奇偶校验位.
Just to clarify, the receiver and transmitter use 8 data bits, 1 stop bit, and no parity bit.
推荐答案
我更喜欢 SerialPOSIX 操作系统编程指南.
您应该删除 fcntl(mainfd, F_SETFL)
语句,因为它不是必需的并且执行不正确(F_GETFL 之前没有完成并且缺少第三个参数).
You should delete the fcntl(mainfd, F_SETFL)
statement, since it's not required and incorrectly implemented (F_GETFL not done prior and missing third argument).
尝试使用 cfmakeraw 设置非规范模式,因为您的初始化代码不完整:
Try using cfmakeraw to setup non-canonical mode, since your initialization code is incomplete:
options->c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP
| INLCR | IGNCR | ICRNL | IXON);
options->c_oflag &= ~OPOST;
对于非规范模式,还需要定义
For non-canonical mode, you also need to define
options.c_cc[VMIN] = 1;
options.c_cc[VTIME] = 2;
1 和 2 只是建议值.
1 and 2 are just suggested values.
在所有系统调用之后添加返回状态测试.
Add testing of return status after all system calls.
rc = tcgetattr(mainfd, &options);
if (rc < 0) {
printf("failed to get attr: %d, %s
", mainfd, strerror(errno));
exit (-3);
}
尝试使用较慢的波特率(例如 115200 甚至 9600)进行测试.
Try testing with slower baudrates (e.g. 115200 or even 9600).
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