getting data from a sensor

[cj5cowboy]

Hi,

I have a seismic sensor that I need to hook up to a serial port and start reading data from.
(I don't have much documentation other than a datasheet of the AD converter I found on the net)

Here is what I am trying to do.

The AD converter can be set in a 'mode' (4 different ones single step conversion and continuous conversion combined with a resolution).
There is no response if you set a mode.

Than there are a few commands one can use; status, get a digit pair(a byte) (there are 3 different digit pairs.
The sensor doesn't send any data over the serial link when not asked for it.

Anyway, I am trying to send one byte commands and try to retriven one byte responses but I seem to get a lot of 'Resource temporarily unavailable' messages when I try to read the data.

what would be the best way to talk to that sensor so that I don't get those EAGAIN 'Resource temporarily unavailable' erros ?

thanks,

Ron

Oh I am using C btw.

[oneofmany]

what programming language are you using? how have you configured the port and how are you accessing it?

[cj5cowboy]

I am using C (I think I mentioned that).

I disassembled the sensor to look at it, it only uses pin 2,3 and 5 (so there is no handshakes or flow control) The data is binary, so xon/xoff won't work either.

here is how I open the port:
int OpenSeismoPort(char *dev)
{
char sPortName[64];

sprintf(sPortName, "/dev/%s", dev);
#ifdef DEBUG
printf("sPortName=%s\n", sPortName);
#endif

fd = open(sPortName, O_RDWR | O_NOCTTY | O_NDELAY );
if (fd < 0) {
printf("open error:%s %d %s\n", sPortName, errno, strerror(errno));
}
else
{
struct termios options;

// Get the current options for the port...
tcgetattr(fd, &options);

// Set the baud rates to 19200...
cfsetispeed(&options, B19200);
cfsetospeed(&options, B19200);

// Enable the receiver and set local mode...
options.c_cflag = B19200 | CLOCAL | CREAD | CS8 | PARENB;

options.c_cflag &= ~CSTOPB; // one stop bit

options.c_lflag &= ~ICANON; // binary data non canonical

options.c_cc[VTIME] = 0; // we're not using the inter character timer
options.c_cc[VMIN] = 1; // blocking read until 1 character arrives


tcflush(fd, TCIFLUSH);
// Set the new options for the port...
tcsetattr(fd, TCSANOW, &options);
}
return fd;
}

than reading and writing I just use write and read.
Somebody once got it to work on an msdos/windows95 machine. The sensor is pretty old ('95) and the company that built them is not in business anymore.

The msdos app probably used things like outportb/inportb at the time. (I remember that being kinda popular in those turbo-c days)

Is that something I should use ?, outb_p, inb_p ? Is that 'more direct' ?

thanks for your reply,

Ron

[oneofmany]

its been a while since i used raw c but if i remember correctly, reads and writes are buffered so that's probably not a good option. also, try lowering your baud rate to something like 9600 and seeing if that has any affect. back in the 95 days that was considered "compatibility" speed.

if you still have the original driver/software available you could try using that with a breakout box and seeing what the data flow is like too.

[cj5cowboy]

I did that, I installed it on an old pc and looked at what teh data did. it is what I expected (after reading the data sheet). However .. when I snooped that serial port on a windows machine I didn't see any serial line problems.

I rewrote some stuff to see what is going on. it seems at some point that 'nothing happens'.

What I try and do is close the serial port (with a close(fd)) and than open it again.

It seems that closing the port takes forever (well almost forever.)
that pretty much indicates something must be wrong I think

I tried setting the speed of the port and device to 9600 doesn't make a difference.
(I also tried several different pc's to

[cj5cowboy]

I figured it out, I needed the nodelay option is the tio.c_oflag member of termios too.