HP Serial Port Problem

Posted on 2013-11-19
Last Modified: 2013-11-23
I have HP EliteBook 8570p Notebook
The serial port on the laptop has a problem , when i connect any device to configure it on that serial port , the messages that have been output from the device appears normally , but when i tried to write anything via my keyboard it does not response to any key of keyboard ,  so the com port can read but cannot write.

Trouble Shooting:
1. i installed windows again , the same problem.
2. i used another software differ from hyper terminal , such like Tera term , putty , and the same.
3. i tried many routers , switches from different vendors to see if the problem from the device not the serial port of laptop , but the same
4. i've updated the bios and all the drivers to latest version , and the same.
Question by:EngAhmedFaris
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
  • 4
  • 3
LVL 13

Expert Comment

by:Norm Dickinson
ID: 39662167
Serial ports are pretty much the opposite of plug and play. You need to set the communications protocols for the particular device you are plugging into the port for speed, parity, stop bit, etc. and there are a lot of combinations. Both devices need to have the exact same settings for the communication to take place correctly. Here is a link to a basic guideline for setting serial communications:

Author Comment

ID: 39662192
I already verify that the COM port has the same settings on the device need to be configured , but i think if there is mis-configuration it will not read from the device , but in my case the COM port read normally from the device but do not write any thing.
LVL 13

Expert Comment

by:Norm Dickinson
ID: 39662372
Perhaps you need a different cable? Some RS-232 cables do not carry all of the signals from end to end, but rather loop back on the same end to provide false feedback to the port.  See
Independent Software Vendors: 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: 39662694
I changed 3 console cables , and the same problem
LVL 13

Expert Comment

by:Norm Dickinson
ID: 39662819
Again, not all cables are designed for full communications across the cable from one end to the other, so it may not be a "bad" cable but one that is designed for only partial communication. It may be worthwhile to pin out the cable with an ohm-meter to determine whether the necessary pins on one end connect to the pins on the other end. Most inexpensive serial cables shortcut this by assuming there will be a signal, so some pins are not cabled thru, but instead the signal on one end is shorted to a different pin on the same end. It is a little confusing but this may help to explain it a little better.

Author Comment

ID: 39663033
I have usb to serial connector , and i used these cables with that connector and it works perfectly.
LVL 13

Accepted Solution

Norm Dickinson earned 500 total points
ID: 39663464
Have you tested the port with a loopback plug and diagnostic software to see if in fact the hardware is functioning correctly?

Featured Post

Free learning courses: Active Directory Deep Dive

Get a firm grasp on your IT environment when you learn Active Directory best practices with Veeam! Watch all, or choose any amount, of this three-part webinar series to improve your skills. From the basics to virtualization and backup, we got you covered.

Question has a verified solution.

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

Suggested Solutions

Title # Comments Views Activity
Telepresence on backup 3 82
HP 15-D068CA Laptop Repair Manual 5 46
Unable to enable HWIC 2FE 2 31
Router Issue? 9 33
In this article you will get to know about pros and cons of storage drives HDD, SSD and SSHD.
How to set-up an On Demand, IPSec, Site to SIte, VPN from a Draytek Vigor Router to a Cyberoam UTM Appliance. A concise guide to the settings required on both devices
After creating this article (, I decided to make a video (no audio) to show you how to configure the routers and run some trace routes and pings between the 7 sites…
Finding and deleting duplicate (picture) files can be a time consuming task. My wife and I, our three kids and their families all share one dilemma: Managing our pictures. Between desktops, laptops, phones, tablets, and cameras; over the last decade…

752 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