c-code for parallax rfid reader on raspberry pi - c

Question

I've searched for quite some time now for a solution to my problem.
I'd like to read RFID tags on my Raspberry, but I want to do it in C-code, as the rest of my project is written in C.
I have a few questions to the following C-code I found here on stackoverflow.com:
What .h includes do I need for the code below?
Where is the interface setup, that I'm using? (/dev/ttyAMA0)
Please help me to get this code snippet working right, as it's been holding me up for a few days already.
char read_rfid(char* rfid_num) {
fd_set input_fdset;
ssize_t length;
int done;
for(done=0; done < 14; ) {
FD_ZERO(&input_fdset);
FD_SET(fd,&input_fdset);
if(select(fd+1 ,&input_fdset, NULL,NULL,NULL) == -1) {
if (errno == EAGAIN) continue;
perror("Terminal select() failed");
return -1;
}
if(FD_ISSET(fd,&input_fdset)) {
if((length = read(fd,rfid_num+done,14-done)) == -1) {
if (errno == EAGAIN) continue;
perror("Terminal: read() failed");
return -1;
}
write(STDOUT_FILENO,rfid_num+done,length);
done += length;
}
}
return 0;
}
int setupRS232()
{
struct termios term_attr;
if((fd = open(RFID,O_RDWR)) == -1)
{
perror("Can't open Device");
return(1);
}
if(tcgetattr(fd,&term_attr) != 0)
{
perror("terminal: tcgetattr() failed");
return(1);
}
term_attr.c_cflag = BAUD|CS8|CRTSCTS|CLOCAL|CREAD;
term_attr.c_iflag = 0;
term_attr.c_oflag = 0;
term_attr.c_lflag = 0;
if(tcsetattr(fd,TCSAFLUSH,&term_attr) != 0)
{
perror("terminal: tcsetattr() failed");
return(1);
}
}
int main(int argc, char** argv)
{
char rfid_num[14];
int i;
if(setupRS232() == 1)
return(1);
puts("Waiting for transponder...");
read_rfid(rfid_num);
for(i=0;i<20;i++)
{
printf("%x\n",rfid_num[i]);
}
}

Answer 1

#include <unistd.h> // for read & write functions
#include <sys/select.h> // fd_set functions
#include <stdio.h> // for perror & printf family
#include <sys/types.h> // for open related function
#include <sys/stat.h> // for open related function
#include <fcntl.h> // for open related function
#include <termios.h> // for terminal functions
#include <errno.h> // for error code
#define RFID "path_to_rfid" // FIXME <- you should set this properly
char read_rfid(char* rfid_num, int fd)
{
fd_set input_fdset;
ssize_t length;
int done;
for(done=0; done < 14; ) {
FD_ZERO(&input_fdset);
FD_SET(fd,&input_fdset);
if(select(fd+1 ,&input_fdset, NULL,NULL,NULL) == -1) {
perror("Terminal select() failed");
return -1;
}
if(FD_ISSET(fd,&input_fdset)) {
if((length = read(fd,rfid_num+done,14-done)) == -1) {
perror("Terminal: read() failed");
return -1;
}
write(STDOUT_FILENO,rfid_num+done,length);
done += length;
}
}
return 0;
}
int setupRS232()
{
struct termios term_attr;
int fd = 0;
if((fd = open(RFID,O_RDWR)) == -1) {
perror("Can't open Device");
return(-1);
}
if(tcgetattr(fd,&term_attr) != 0)
{
perror("terminal: tcgetattr() failed");
close(fd);
return(-1);
}
term_attr.c_cflag = CBAUD|CS8|CRTSCTS|CLOCAL|CREAD;
term_attr.c_iflag = 0;
term_attr.c_oflag = 0;
term_attr.c_lflag = 0;
if(tcsetattr(fd,TCSAFLUSH,&term_attr) != 0) {
perror("terminal: tcsetattr() failed");
close(fd);
return(-1);
}
return (fd);
}
int main(int argc, char** argv)
{
char rfid_num[14];
int i;
int fd;
if((fd = setupRS232()) == -1) {
return(-1);
}
puts("Waiting for transponder...");
read_rfid(rfid_num, fd);
for(i=0;i<20;i++) {
printf("%x\n",rfid_num[i]);
}
return 0;
}
Now your code is ready to be compiled, at least in my machine I could compile with no errors.