Vxworks Serial Port Example
Download Serial Port Reader/Writer for free. Only updated to add downloading of.exe An application in.NET 2.0 that allows reading and writing from or to any serial port on a computer. This is a simple interface that reads lines from a serial port and allows writing single or multiple bytes of data to the serial port.
I am having trouble reading data from the serial port. If I call read, the call is blocked until the number of bytes specified are available. This is fine for terminal-based I/O, which I use in certain circumstances where I'll just read one character at a time (typed by a user on HyperTerm for example). But now I want to read raw data coming from another program over the serial port. The problem I'm having is: A call to ioctl with the FIONREAD command tells me how much data is in the input buffer, which appears to be working just fine.
Now I want to read that data, but calling read just blocks indefintely, never returning the data that's supposed to be in the buffer. Can anyone tell me why this isn't working, and what I must do to make it work correctly? Thanks, Dennis Bruce 00:00. Dennis Jones wrote in message news:37374D47.7A468D34@tektronix.com. I am having trouble reading data from the serial port. If I call read, the call is blocked until the number of bytes specified are available.
This is fine for terminal-based I/O, which I use in certain circumstances where I'll just read one character at a time (typed by a user on HyperTerm for example). But now I want to read raw data coming from another program over the serial port. The problem I'm having is: A call to ioctl with the FIONREAD command tells me how much data is in the input buffer, which appears to be working just fine. Now I want to read that data, but calling read just blocks indefintely, never returning the data that's supposed to be in the buffer.
Can anyone tell me why this isn't working, and what I must do to make it work correctly? ThanksDennis What about something like this: fdset rd; int s; struct timeval t; t.tvsec = t.tvusec = 0; s = fileno(stdin); FDSET(s, &fd); if (select(soc+1, &fd, NULL, NULL, &t) 0) read(.); else /. No data this time! Charlie Grames 00:00.
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Dennis, Is your serial port set up for raw I/O? If not, the driver may be pending for a carriage return. You can use an ioctl to set the serial port for raw I/O after it has been opened: status = ioctl (fd, FIOOPTIONS, OPTRAW); HTH Charlie Grames The Boeing Company (314) 233-1956 Newsgroups: comp.os.vxworks Subject: reading from serial port Date: Mon, 10 May 1999 21:21:20 GMT From: Dennis Jones Organization: Tektronix, Inc. Message-ID: Help! I am having trouble reading data from the serial port.
If I call read, the call is blocked until the number of bytes specified are available. This is fine for terminal-based I/O, which I use in certain circumstances where I'll just read one character at a time (typed by a user on HyperTerm for example). But now I want to read raw data coming from another program over the serial port. The problem I'm having is: A call to ioctl with the FIONREAD command tells me how much data is in the input buffer, which appears to be working just fine. Now I want to read that data, but calling read just blocks indefintely, never returning the data that's supposed to be in the buffer. Can anyone tell me why this isn't working, and what I must do to make it work correctly? Thanks, Dennis Peter 00:00.
Dennis Jones wrote: Help! I am having trouble reading data from the serial port.
If I call read, the call is blocked until the number of bytes specified are available. This is fine for terminal-based I/O, which I use in certain circumstances where I'll just read one character at a time (typed by a user on HyperTerm for example).
But now I want to read raw data coming from another program over the serial port. The problem I'm having is: A call to ioctl with the FIONREAD command tells me how much data is in the input buffer, which appears to be working just fine.
Now I want to read that data, but calling read just blocks indefintely, never returning the data that's supposed to be in the buffer. Can anyone tell me why this isn't working, and what I must do to make it work correctly? Thanks, Dennis What you have decribed here sounds very similar to something that I needed to do. For our application, we are using the console port, and did not want the characters echoed to the terminal, or to be blocked. To accomplish this, I set up the serial port with the following: IStatus = ioctl ( STDIN, FIOSETOPTIONS, OPTTERMINAL & OPTLINE & OPTECHO ); After this initialization, I read the serial port character by character. Char.COMMANDChar;.COMMANDChar = getchar ; The getchar function waits until a character is pressed, but does not 'block' until the EOL.
Hope this helps, - Peter - E-mail: (home) - Jeff Szczepanski 00:00. I agree with Charlie Grames.
I think you really want to be running the serial port in RAW mode using the IOCTL. However, the one problem that you typically have here is that the serial port is too slow relative to the CPU, especially at the lower baud rates. Ie: Every time you do a read, you only get a few characters maximum and moving lots of data can be rather task switch intensive getting the characters as they trickle in on the serial port. A few simple modifications to the serial driver can make the IO very efficient. The basic idea is to setup a watchdog timer in the driver that is setup to expire after a few character receive periods elapse on the serial port at the current baud rate. The watchdog is restarted after each new character comes in, but select is not triggered in the driver until one of two things occurs in the driver: a) The receive ring buffer is nearly full; or b) the watchdog expires.
At the task level you block on select and wait for it to fire off. When you do the read you will always get a full ring buffer full of data or have all the data up to the point in the receive stream where there was an interruption in the transmission. In other words you never have to worry about the received data becoming 'stale', but the data is always moved in as chunky as a fashion as possible. Regards, Jeff Jeffrey R. Szczepanski InSciTek Microsystems, Inc. 635 CrossKeys Office Park Fairport, NY 14450 Phone: 716-421-3850 Bruce wrote in message.
In comp.os.vxworks Dennis Jones wrote: I am having trouble reading data from the serial port. If I call read, the call is blocked until the number of bytes specified are available. This is fine for terminal-based I/O, which I use in certain circumstances where I'll just read one character at a time (typed by a user on HyperTerm for example). But now I want to read raw data coming from another program over the serial port. The problem I'm having is: A call to ioctl with the FIONREAD command tells me how much data is in the input buffer, which appears to be working just fine.
Now I want to read that data, but calling read just blocks indefintely, never returning the data that's supposed to be in the buffer. Can anyone tell me why this isn't working, and what I must do to make it work correctly? It would be a little easier if code was posted. Are you saying that you do an ioctl that returns n bytes available, and when you attempt to read n bytes, it blocks? That is certainly the way I've done it before.
Dennis Jones 00:00. Bruce wrote: In comp.os.vxworks Dennis Jones wrote: I am having trouble reading data from the serial port. If I call read, the call is blocked until the number of bytes specified are available. This is fine for terminal-based I/O, which I use in certain circumstances where I'll just read one character at a time (typed by a user on HyperTerm for example).
Vxworks Serial Port Example Code
But now I want to read raw data coming from another program over the serial port. The problem I'm having is: A call to ioctl with the FIONREAD command tells me how much data is in the input buffer, which appears to be working just fine.
Now I want to read that data, but calling read just blocks indefintely, never returning the data that's supposed to be in the buffer. Can anyone tell me why this isn't working, and what I must do to make it work correctly?
Parallel Port
It would be a little easier if code was posted. Are you saying that you do an ioctl that returns n bytes available, and when you attempt to read n bytes, it blocks? That is certainly the way I've done it before.
That's exactly right. Basically, I do something like this: ioctl( fd, FIONREAD, &n ); read( fd, data, n ); I have tried: ioctl( fd, FIOSETOPTIONS, OPTRAW ) to make sure the port is in RAW mode, but this does not help. If another task has an open file descriptor on the port, would that result in the kind of behavior I'm seeing? Some more background may be in order: I want to have exclusive access to the port while my task is running. I know it is safe to do so, but I think another task already has an open file descriptor for the port. I need to prevent that task from using the port while my task executes.
This necessitates (I think) some way of determining: a) if the port is, in fact, already in use, and b) which task is using it (so I can suspend it temporarily). My task should start out using the port in the normal terminal mode, and should switch to raw mode upon receipt of a special character (which I've defined to be 0x80).
After I'm through with it, it should switch back to terminal mode, at which time I will need to give up the port so other tasks (if any) can use it. Does this make sense, and is it a reasonable process? Thanks for the replies so far. I'm a VxWorks newbie and sure do appreciate your generous responses.
Dennis Jones Tektronix, Inc.