Serial write timeout?

Posted on 2001-08-13
Medium Priority
Last Modified: 2008-02-26

I am trying to send data through the serial port. I'm not having any problems with that, but how can I detect when something goes wrong while writing data to it?

Currently I am writing data to it one byte at a time. If, during a large transmission, I disconnect the serial cable, my program just hangs on the write command. Is there any way to set up a timeout period for the write operation?

I am just using the standard write command with a file descriptor.

Question by:dwagner
Welcome to Experts Exchange

Add your voice to the tech community where 5M+ people just like you are talking about what matters.

  • Help others & share knowledge
  • Earn cash & points
  • Learn & ask questions

Expert Comment

ID: 6383660
I guess this relates to your problem as well...?


and look for:
while (STOP==FALSE) {     /* loop until we have a terminating condition */

Author Comment

ID: 6383825

It is a little different in my case because I am writing rather than waiting for input. As far as I can see there is no way to automatically have a timeout value for writing to a resource.

However, I solved my own problem. I now access the serial port in non-blocking mode (using the O_NONBLOCK flag when opening it) instead of a blocking mode.

I then have a little bit of code that tries to write a byte to the resource for a specified period of time. If it fails because the file is busy it will try sending again. It gives up after an unexpected error or the time I want to retry for has been exceeded.

Kind of simple when I thought of it. I should have waited those 5 minutes longer before posting here :)

Thanks for your help though. I'll leave this question open in case anyone has a better solution.


Expert Comment

ID: 6383834
What about using checksum, after you've sent the data, could you then retrieve it and compare the checksum?

This a just a wild stab in the dark.

Regards Mike
Technology Partners: We Want Your Opinion!

We value your feedback.

Take our survey and automatically be enter to win anyone of the following:
Yeti Cooler, Amazon eGift Card, and Movie eGift Card!


Author Comment

ID: 6384276

That would spot corrupt data but wouldn't help the original problem of having a "write" just hang if transmission was interupted (for example by ripping the serial cable out of the port like I did :).

I'm not too worried if the machine at the other side of the serial cable receives the data OK. It can work that out from a CRC transmitted with the data and then it can decided if it wants to try getting the data again.

CRCs... I still don't fully understand the maths... Good job there is plenty of source code out there that I can use :)

LVL 20

Expert Comment

ID: 9915896
No comment has been added lately, so it's time to clean up this TA.
I will leave the following recommendation for this question in the Cleanup topic area:

PAQ with points refunded

Please leave any comments here within the next seven days.

EE Cleanup Volunteer

Accepted Solution

modulo earned 0 total points
ID: 9963594
PAQed, with points refunded (100)

Community Support Moderator

Featured Post

[Webinar] Lessons on Recovering from Petya

Skyport is working hard to help customers recover from recent attacks, like the Petya worm. This work has brought to light some important lessons. New malware attacks like this can take down your entire environment. Learn from others mistakes on how to prevent Petya like worms.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Have you ever been frustrated by having to click seven times in order to retrieve a small bit of information from the web, always the same seven clicks, scrolling down and down until you reach your target? When you know the benefits of the command l…
The purpose of this article is to fix the unknown display problem in Linux Mint operating system. After installing the OS if you see Display monitor is not recognized then we can install "MESA" utilities to fix this problem or we can install additio…
Monitoring a network: how to monitor network services and why? Michael Kulchisky, MCSE, MCSA, MCP, VTSP, VSP, CCSP outlines the philosophy behind service monitoring and why a handshake validation is critical in network monitoring. Software utilized …
In this video, Percona Solutions Engineer Barrett Chambers discusses some of the basic syntax differences between MySQL and MongoDB. To learn more check out our webinar on MongoDB administration for MySQL DBA: https://www.percona.com/resources/we…
Suggested Courses
Course of the Month8 days, 22 hours left to enroll

764 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question