У меня есть программа на C:
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <time.h> // clock_gettime
#include <signal.h> // obsluha signalu
// Linux headers
#include <fcntl.h> // Contains file controls like O_RDWR
#include <errno.h> // Error integer and strerror() function
#include <termios.h> // Contains POSIX terminal control definitions
#include <unistd.h> // write(), read(), close()
// Global variable
int ser_1; // Serial port
bool cykl=true; // Podmínka trvani nekonecneho cyklu
void init_serial_1()
{
// Nastaví sériový port ttyS1
// 8bit
// None parita
// 1 start
// 1 stop
// 9600
// Open the serial port. Change device path as needed (currently set to an standard FTDI USB-UART cable type device)
ser_1 = open("/dev/ttyS1", O_RDWR);
// Create new termios struc, we call it 'tty' for convention
struct termios tty;
memset(&tty, 0, sizeof tty);
// Read in existing settings, and handle any error
if(tcgetattr(ser_1, &tty) != 0) {
printf("Error %i from tcgetattr: %s\n", errno, strerror(errno));
}
tty.c_cflag &= ~PARENB; // Clear parity bit, disable parity
tty.c_cflag &= ~CSTOPB; // Clear stop field, only one stop bit used in communication (most common)
tty.c_cflag |= CS8; // 8 bits per byte (most common)
tty.c_cflag &= ~CRTSCTS; // Disable RTS/CTS hardware flow control (most common)
tty.c_cflag |= CREAD | CLOCAL; // Turn on READ & ignore ctrl lines (CLOCAL = 1)
tty.c_lflag &= ~ICANON;
tty.c_lflag &= ~ECHO; // Disable echo
tty.c_lflag &= ~ECHOE; // Disable erasure
tty.c_lflag &= ~ECHONL; // Disable new-line echo
tty.c_lflag &= ~ISIG; // Disable interpretation of INTR, QUIT and SUSP
tty.c_iflag &= ~(IXON | IXOFF | IXANY); // Turn off s/w flow ctrl
tty.c_iflag &= ~(IGNBRK|BRKINT|PARMRK|ISTRIP|INLCR|IGNCR|ICRNL); // Disable any special handling of received bytes
tty.c_oflag &= ~OPOST; // Prevent special interpretation of output bytes (e.g. newline chars)
tty.c_oflag &= ~ONLCR; // Prevent conversion of newline to carriage return/line feed
// tty.c_oflag &= ~OXTABS; // Prevent conversion of tabs to spaces (NOT PRESENT ON LINUX)
// tty.c_oflag &= ~ONOEOT; // Prevent removal of C-d chars (0x004) in output (NOT PRESENT ON LINUX)
tty.c_cc[VTIME] = 10; // Wait for up to 1s (10 deciseconds), returning as soon as any data is received.
tty.c_cc[VMIN] = 0;
// Set in/out baud rate to be 9600
cfsetispeed(&tty, B9600);
cfsetospeed(&tty, B9600);
// Save tty settings, also checking for error
if (tcsetattr(ser_1, TCSANOW, &tty) != 0) {
printf("Error %i from tcsetattr: %s\n", errno, strerror(errno));
}
/*
// Write to serial port
unsigned char msg[] = { 'H', 'e', 'l', 'l', 'o', '\r' };
write(ser_1, "Hello, world!", 13);
// Allocate memory for read buffer, set size according to your needs
char read_buf [256];
memset(&read_buf, '\0', sizeof(read_buf));
// Read bytes. The behaviour of read() (e.g. does it block?,
// how long does it block for?) depends on the configuration
// settings above, specifically VMIN and VTIME
int num_bytes = read(ser_1, &read_buf, sizeof(read_buf));
// n is the number of bytes read. n may be 0 if no bytes were received, and can also be -1 to signal an error.
if (num_bytes < 0) {
printf("Error reading: %s", strerror(errno));
}
// Here we assume we received ASCII data, but you might be sending raw bytes (in that case, don't try and
// print it to the screen like this!)
printf("Read %i bytes. Received message: %s", num_bytes, read_buf);
close(ser_1);*/
}
// Obsluha signálu
void sigint_handler(int sugnum)
{
cykl=false;
}
float difftimespec(struct timespec *ts1, struct timespec *ts2)
{
return difftime(ts1->tv_sec,ts2->tv_sec) + (ts1->tv_nsec - ts2->tv_nsec)*1e-9;
}
// Hlavní program
int main()
{
// Mereni casu, zacatek
struct timespec time_start, time_actual;
clock_gettime(CLOCK_MONOTONIC, &time_start);
// Inicializace obsluhy signalu
signal(SIGINT, sigint_handler);
// Inicializace serioveho portu
init_serial_1();
// Buffer pro cteni
char read_buf [256];
memset(&read_buf, '\0', sizeof(read_buf));
int num_bytes; // Nuber of read charakters
// Otevreni souboru pro data
FILE *file;
file=fopen("data.txt","a+t"); //apend, read, write, text
// Cyklicky se opakujíci cast
while(cykl)
{
// Get actual time
clock_gettime(CLOCK_MONOTONIC, &time_actual);
fprintf(file, "Start: %.9f\n",difftimespec(&time_start,&time_actual));
printf("Dalsi kolo: %.9f\n", difftimespec(&time_start,&time_actual));
write(ser_1,"Ra\0",3); // write to serial command
clock_gettime(CLOCK_MONOTONIC, &time_actual);
fprintf(file, "-----: %.9f\n",difftimespec(&time_start,&time_actual));
num_bytes = read(ser_1, &read_buf, sizeof(read_buf));
clock_gettime(CLOCK_MONOTONIC, &time_actual);
printf("Vymena dat: %.9f\n", difftimespec(&time_start,&time_actual));
printf("ReadMessage:%s %d\n", read_buf, num_bytes);
fprintf(file, "After: %.9f %s\n",difftimespec(&time_start,&time_actual),read_buf);
}
close(ser_1);
fclose(file);
printf("\n\n Konec ...\n");
}
Программа связывается с процессором AVR. Программа работает на одноплатной плате P C. Время связи здесь: Время связи
- Почему задержка между приемом и передачей?
- Проблема в
read(ser_1, &read_buf, sizeof(read_buf)); Эта команда заканчивается через 4 мс после последний персонаж Почему? - Неправильная настройка порта?