SiLab Driver Registers With Invalid COM Port Number (COM351)

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alexanlu
 
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SiLab Driver Registers With Invalid COM Port Number (COM351)

Post by alexanlu »

We use Adafruit's Raspberry Pi USB dongle to connect our device to the windows PC, and have installed the CP210X driver from the following product website:

https://learn.adafruit.com/adafruits-ra ... on-windows

Well this works in most cases, we encountered issued in a certification lab where the SiLab driver registers the COM port with number 351, which is not valid (max 256 on windows), and as a result we could not connect to the device through serial applications such as Tera Term, which can not list the device with proper COM setting. In the attached screen shot, you can see the (COM351) under Windows Device Manger at the bottom left, and without a properly configured matching port on Tera Term

Do you know why this might be happening, and could suggest ways to work around it?
CP210_wrong_com_port.jpg
CP210_wrong_com_port.jpg (69.78 KiB) Viewed 82 times

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freddyboomboom
 
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Re: SiLab Driver Registers With Invalid COM Port Number (COM

Post by freddyboomboom »

Windows will keep a running list of each individual serial port (and network port, and...) and increment that number each time it discovers a new one.

You can "show hidden devices" and remove the ones that are not currently connected, including com351, and when it is reconnected, or the devices refreshed, it should give it a lower number.

Or you can reinstall Windows.

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alexanlu
 
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Re: SiLab Driver Registers With Invalid COM Port Number (COM

Post by alexanlu »

The problem is understood. Since the certification lab PC has been testing with hundreds of devices, the COM port registry eventually gets filled up, and going over 256. It seems to be a problem with Windows not clearing or released the COM port for devices that are no longer present. The problem can be fixed by manually deleting Computer\HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\COM Name Arbiter\ComDB through Registry Editor, then reboot the PC.

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