Really high IRQ values???

scrawny_1 · 12-01-2008, 05:57 PM

I decided to place this question in the newbie section as it's probably a no-brainer.

I have attached a serial PCI card to my RHEL4 linux machine and the IRQ assigned to it is 209. Which seems rather high. The IO is 0x2440. Is this right? I thought interrupts only went so far. Also it's not in the IRQ table in /proc/interrupts.

dmesg | grep tty gives this:
ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
ttyS4 at I/O 0x2440 (irq = 209) is a 16550A

The new device is ttyS4. I need it to talk to an old allen bradley box but it's not working. How do I know if it's "installed" correctly?

Have tried assigning a lower IRQ and IO with 'setserial' which has produced erroneous results.

Please help.

-Scrawny

norobro · 12-03-2008, 10:12 AM

Let me start off by saying that I know very little about this.

I have a Davis Vantage Pro II weather station plugged into com1 and it just worked. I communicate with it using C++ programs that I have written.

What are you using to communicate with your A-B box?

To troubleshoot, can you unplug whatever you have hooked to com1 and try your A-B box there?

scrawny_1 · 12-08-2008, 10:27 PM

Hi! I use some C code to open and read the port. It's falling over at a read statement:
status = read(iodevfdes,&c,1);
According to the 'read' function in unistd.h '-1' is 'errors'.

Here's the code:

*/
/*
** openpd open protocol handler device port
**
*/

#define IOSECS 8 /* seconds to wait for IO completion */

#include "/u/t35/include/global.h"
#include "/u/t35/include/config.h"
#include <sys/ioctl.h>
#include <stdio.h>
#include <signal.h>
#include <fcntl.h>
#include <termio.h>
#include <unistd.h>

/*
** global variables describing the device
*/
extern char *iodevname; /* device name (see configure) */
extern uint iodevioctl; /* required ioctl parameters (see configure) */
extern int iodevfdes; /* device file descriptor */
extern char evstr[];

void onint();

openpd()
{
extern void exit();
struct termio iob;

/*
* open the device as indicated in the config table
* and setup the file descriptor
*/

if ((iodevfdes=open(iodevname,O_RDWR|O_NONBLOCK)) == BAD_OPEN) {
sprintf(&evstr[0],"AMGR: Openpd : can't open %s\n",iodevname);
frrlog(&evstr[0]);
exit(-1);
}

sprintf(&evstr[0],"AMGR: Openpd: iodevname <%s>\n",iodevname);
frrlog(&evstr[0]);
sprintf(&evstr[0],"AMGR: Openpd: iodevioctl <%ld>\n",iodevioctl)
;
frrlog(&evstr[0]);
sprintf(&evstr[0],"AMGR: Openpd: iodevfdes <%ld>\n",iodevfdes);
frrlog(&evstr[0]);
/*
* set up the opened port for RAW i/o
*/

if (ioctl(iodevfdes,TCGETA,&iob) == ERROR) {
sprintf(&evstr[0],"AMGR: Openpd: can't ioctl %s\n",iodevname);
frrlog(&evstr[0]);
exit(-1);
}

iob.c_cflag = iodevioctl; /* tty control word */

iob.c_iflag &= ~IGNPAR; /* ignore parity errors */
iob.c_iflag &= ~INPCK; /* disable parity check */
iob.c_iflag &= ~BRKINT; /* ignore line breaks */
iob.c_iflag &= ~ISTRIP; /* don't strip bit 8 */

iob.c_oflag &= ~OPOST; /* no post process on o/p*/

iob.c_lflag = 0 ;
iob.c_cc[4] = (char)1; /* MIN number of characters */
iob.c_cc[5] = (char)50; /* Time out .3 secs */

if (ioctl(iodevfdes,TCSETA,&iob) == ERROR) {
sprintf(&evstr[0],"AMGR: Openpd: can't ioctl %s", iodevname);
frrlog(&evstr[0]);
exit(-1);
}

(void)ioctl(iodevfdes,TCFLSH,0);

}

/***********************************************************************
*
* getcpd - gets a character from the handler's protocol device
*
**********************************************************************/

getcpd()
{
extern int status;
char c;
long time();
uint alarm();

#define DLEN 120
static char dbuf[DLEN];
static char *dp = &dbuf[0];
static char *dop;
static int dcnt;
char df, dc;

try_again:
(void)signal(SIGALRM,onint); /* set alarm signal for trap by onint*/
(void)alarm(IOSECS);

status = read(iodevfdes,&c,1);

(void)alarm(0);
(void)signal(SIGALRM,SIG_IGN);

if (status == -1) {
sprintf(&evstr[0],"AMGR: Getcpd (amgr): -1 status\n");
frrlog(&evstr[0]);
return (IO_TIMEOUT);
} else if (status == 0) {
sprintf(&evstr[0],"AMGR: Getcpd (amgr): 0 status\n");
frrlog(&evstr[0]);
sleep(1);
goto try_again;
} else {
return (c & 0377);
}
}

norobro · 12-10-2008, 10:54 AM

I'm not clear whether your program is making it to this line:

Code:

if (status == -1)

or not. If it is, could the following be your problem?

Quote:

From here:

"If a non-blocking instruction tries to read a port, if no data is available, it will normally return an error or status indicator and allow the program to continue."

scrawny_1 · 12-15-2008, 05:50 AM

Hmmmm... interesting point. The code does get to that point. I have inserted a couple of debug statements and the code:

Code:

sprintf(&evstr[0],"AMGR: Getcpd (amgr): -1 status\n");
frrlog(&evstr[0]);

writes the string to an error dump file.

I keep thinking it might be the hardware...

Would the BAUD rate or the error checking or the XON/XOFF have anything to do with it?

norobro · 12-15-2008, 09:45 AM

Could be the hardware. As I stated above I'm no expert, but ...

My serial device does not send data unless I send it a command. If the port is opened O_NONBLOCK, reading from it without sending a command (no data available) returns "-1". If I open and read from it without the O_NONBLOCK flag it returns "0"

Seems to me you need to either remove the O_NONBLOCK from the open statement or change the code in the getcpd function to something like

Code:

while ( x < 60 ) // a counter for how long you wait for data
{
status = read(iodevfdes,&c,1);

if (status == -1 ) sleep(1);
   else return (c & 0377);
x++;
}
return (IO_TIMEOUT);