Serial Communications on Modern Laptops
One of the problems technicians face today is having to use modern computers to talk to legacy equipment. Most Radio equipment in use requires serial connections to communicate between the computer and the device. Most new laptops do not include a native serial com port. Technicians can use USB to serial adapters to accomplish this task however this solution comes with its own set of problems.
Some challenges that you may face include:
1.Com ports get hung up by software
2. USB adapters may be assigned a higher number than what the older program can recognize
3. Com ports show up as in use even though there is nothing plugged in
4. Com ports that are in use don’t show up in the device manager.
5. USB adapter drivers may not be installed on the computer.
6. USB adapter chipset is not compatible with the device
Where to go to solve com port issues
To resolve issues with com ports, we need to navigate to the Device manager. In windows 8.1 and above, the easiest way to get to the device manager is to right click on the start menu icon. Then select device manager. Once we get to the device manager we can select Port and we can see the com ports installed in our computer. If the drivers are not installed you may not see the com port listed here.
Resolving com ports that are hung up
Now at times a com port can get hung up with software. This will render the com port unusable. Typically you will see this happen if the com port gets unplugged during communication or if the software gets unexpected errors and can’t deal with them. To resolve this, you can close the software used with the com port such are radio programming software then right click on the com port in the device manager listed under ports. Click on disable. Click yes on the pop up. Once this is done right click on the port and click enable to make the port available again. The port should now be back in normal operation.
High numbers issued to com ports that older programs can’t see.
Older programs were written with the idea that you wouldn’t have more than a handful of serial devices plugged in at once. This was back when computers didn’t multitask as well and in most cases you just didn’t see a need to have more than 4 ports. Many older programs will only look for com port 1 thru 4. This becomes a problem because when you plug in a USB to serial adapter you may be issues Com port number 19 or some higher number that the software can’t see. To Resolve this we can reassign the com port to a lower number. To do this go to the device manager and find the USB adapter that has a high number assigned to it. Right click and go to properties. Under the port settings tab click on the advanced button. You will then see an pick list where you can re-assign the adapter to a lower comm port number that the software can see.
Lower number com ports show as in use
previously we talked about changing the port number on USB adapters. There will be times when you find that the com ports show that they are in use. They may show in use even though there is no software using serial ports at the moment nor is there any other com port adapter plugged in. Computers can remember adapters on usb ports. So the computer holds that port number until the next time the same adapter gets plugged in. Sometimes this is ok but sometimes you have a new adapter you need to get working of you are using a shared laptop with your own adapter. Whatever the case may be, you need to assign your adapter to a com port that shows up as “in use”. If you know that you don’t have any other adapters being used you can select the com port that is in use. Windows will prompt you, saying that this is a bad idea. Go ahead and click ok to assign the com port the lower number. Next what we want t do is disable the com port then re-enable it. We do this to break any association with the old adapter and when we enable to port it will only be associated with the current adapter.
Com ports in use don’t show up in device manager
Sometimes when we go to change a com port number assignment we find that there are many ports listed that we don’t see in the device manager list. If you go to View and select show hidden devices you will be able to see devices that the computer is holding until the device is plugged in again. This will not show all of the devices but will help out in some cases.
USB to Serial adapter drivers
In order for a USB to Serial driver to work well, the correct drivers must be installed on the PC. Windows does a good job at providing many drivers for popular adapters but sometimes this can cause problems. Install any drivers that came with the adapter to ensure best operation. One example of where windows provided drivers can get you in trouble is when you are running windows 8 or above and you have a adapter with a Prolific chipset. Windows will install the latest version drivers and the device won’t work well. A solve for this is to find an older version of the driver. If you install an older version driver, you will need to tell windows that you want to use the older driver. You can do this by going to the device manager, right click on the Serial adapter under ports and choose update drivers. You will get a window asking if you want to search automatically online or Browse your computer. Choose to Browse your computer. Next you will see a path that you can browse and under it you will see a button that says Let me pick from a list of drivers on my computer. Click on the button and at the next window select Ports (COM & LPT). If the drivers were installed correctly you will get a list of drivers for your device. You will be able to choose newer or older versions of your drivers. In the case of the Prolific chipset running on windows 8.1 I have version 126.96.36.199 running.
USB adapter is not compatible with device
There will be times when no matter what you do, you just can’t talk to a device with your USB to serial adapter. This is where having two different adapters with different chipsets come in handy. The two that seem to work well are FTDI and Prolific. If one doesn’t work the other might. One thing to consider when purchasing your adapter is that there are counterfeit products on the market. Try to make sure the adapter you are using has the official chipset.
OLD devices that just won’t die
Sometimes you end up needing to support a device well past its life cycle. Sometimes these devices will have software that was designed for an operating system from 20 years ago and just won’t run on modern OS’s. Sometimes the program will run but the serial connections won’t work. An easy way to deal with this is to try and run an older OS as a Virtual Machine in Vmware or VirtualBox. Many times this solution works great and allows you to support the older device without having to keep a 20 year old laptop. The great thing about Virtual Machines is that when it comes time to upgrade your laptop, all you need to do is transfer the VM file over to the new laptop and you will have the same setup and programs in the VM that you had before.