I've got a strange situation with my C code for linux (ubuntu 19.04), I'm an FPGA developer, mainly I know only HDLs languages, now I've decided to focus on C coding, I have very poor background with C, and would like to write programs that can comunicate with my FPGA. I'm using for this a Basys3 board. I've got a basic UART module, (on FPGA) that on windows works perfectly with TERA TERM. FPGA does this: all what comes from UART goes to a buffer (8 bytes wide), when the first 4 bytes are the binary value of ASCII "data" it saves the remaining 4 bytes into the memory. When I press a button the 4 bytes from the memory are sent to UART Tx. I'm sure that it's sending data: without shutting off the board I load win10 and check on tera term. On ubuntu it just works sometimes. for example: turning on PC, loading bitstream to the FPGA, running C program for sending 8 bytes "data1234", running C uart receiver and pressing the button I get "1234123412341234". shutting off PC, rebooting, doing exactly the same things, can't read anything from UART (pc side).
the previous version of the FPGA bitstream was easier: what comes from UART goes to memory and when I press the button is sent to UART Tx. This works everytime, sending unknown characters, but at least it works, and makes me think that I need some kind of response from UART to enable receiving (pc side), but honestly I don't know..
this is the code that I'm using from an online tutorial and modded. I added some features in some version, but now I'm back to a nearly untouched version.
#include <stdio.h>
#include <fcntl.h> /* File Control Definitions */
#include <termios.h> /* POSIX Terminal Control Definitions */
#include <unistd.h> /* UNIX Standard Definitions */
#include <errno.h> /* ERROR Number Definitions */
void main(void)
{
int fd;/*File Descriptor*/
printf("\n +----------------------------------+");
printf("\n | Serial Port Read |");
printf("\n +----------------------------------+");
/*------------------------------- Opening the Serial Port -------------------------------*/
/* Change /dev/ttyUSB1 to the one corresponding to your system */
fd = open("/dev/ttyUSB1",O_RDWR | O_NOCTTY ); /* ttyUSB0 is the FT232 based USB2SERIAL Converter */
/* O_RDWR - Read/Write access to serial port */
/* O_NOCTTY - No terminal will control the process */
/* Open in blocking mode,read will wait */
if(fd == -1) /* Error Checking */
printf("\n Error! in Opening ttyUSB1 ");
else
printf("\n ttyUSB1 Opened Successfully ");
/*---------- Setting the Attributes of the serial port using termios structure --------- */
struct termios SerialPortSettings ; /* Create the structure */
tcgetattr(fd, &SerialPortSettings); /* Get the current attributes of the Serial port */
/* Setting the Baud rate */
cfsetispeed(&SerialPortSettings,B9600); /* Set Read Speed as 9600 */
cfsetospeed(&SerialPortSettings,B9600); /* Set Write Speed as 9600 */
/* 8N1 Mode */
SerialPortSettings.c_cflag &= ~PARENB; /* Disables the Parity Enable bit(PARENB),So No Parity */
SerialPortSettings.c_cflag &= ~CSTOPB; /* CSTOPB = 2 Stop bits,here it is cleared so 1 Stop bit */
SerialPortSettings.c_cflag &= ~CSIZE; /* Clears the mask for setting the data size */
SerialPortSettings.c_cflag |= CS8; /* Set the data bits = 8 */
SerialPortSettings.c_cflag &= ~CRTSCTS; /* No Hardware flow Control */
SerialPortSettings.c_cflag |= CREAD | CLOCAL; /* Enable receiver,Ignore Modem Control lines */
SerialPortSettings.c_iflag &= ~(IXON | IXOFF | IXANY); /* Disable XON/XOFF flow control both i/p and o/p */
SerialPortSettings.c_iflag &= ~(ICANON | ECHO | ECHOE | ISIG); /* Non Cannonical mode */
SerialPortSettings.c_oflag &= ~OPOST;/*No Output Processing*/
/* Setting Time outs */
SerialPortSettings.c_cc[VMIN] = 32; /* Read at least 10 characters */
SerialPortSettings.c_cc[VTIME] = 5; /* Wait indefinetly */
if((tcsetattr(fd,TCSANOW,&SerialPortSettings)) != 0) /* Set the attributes to the termios structure*/
printf("\n ERROR ! in Setting attributes");
else
printf("\n BaudRate = 9600 \n StopBits = 1 \n Parity = none");
/*------------------------------- Read data from serial port -----------------------------*/
tcflush(fd, TCIFLUSH); /* Discards old data in the rx buffer */
char read_buffer[32]; /* Buffer to store the data received */
int bytes_read = 0; /* Number of bytes read by the read() system call */
int i = 0;
bytes_read = read(fd,&read_buffer,32); /* Read the data */
printf("\n\n Bytes Rxed -%d", bytes_read); /* Print the number of bytes read */
printf("\n\n ");
for(i=0;i<bytes_read;i++) /*printing only the received characters*/
printf("%c",read_buffer[i]);
printf("\n +----------------------------------+\n\n\n");
close(fd); /* Close the serial port */
}
if you can help me finding what is wrong I will love you forever
Thanks
