Bad or Unresponsive USB Connection with Potentiostat

Occasionally a Reference or Interface potentiostat will be plugged into a computer’s USB port and will not be detected. Initially this may lead one to believe the USB communications on the instrument may have failed, and a repair is necessary. However, it may be due to a computer setting known as “USB Selective Suspend Feature”, which may be turned on as a power saving setting in Windows. It is recommended to take the following steps to help determine the source of the USB communications failure.

Quick Physical Check

It is not uncommon for a USB port on the computer to become damaged. A simple way to check this is to insert the USB cable into a port and GENTLY wiggle it up and down. If it feels loose compared to a working USB port on the computer, the port is likely physically damaged and should either be replaced or not used.
The next step is to restart the computer and see if that enables the USB port. Ports on the computer can “go to sleep” and a restart will re-enable them, allowing use of the potentiostat.
If the port is not physically damaged, and the restart does not help, continue reading.

Disabling the Selective Suspend Feature

The Selective Suspend Feature stops power from reaching the port in order to save computer power. In most cases when a USB device is plugged in the port will “wake up” and allow use. However, it is not uncommon for the port to not awake when a device is plugged in. A work around for this is to disable the Selective Suspend Feature. Follow these steps to turn this feature off:

1. Open the Registry Editor by clicking on the Start icon and type regedit in the search box and press Enter. This will open the Registry Editor window.
   
   
   

   Figure 1: Type 'regedit' into the Start menu search bar and press enter to open the Registry Editor

   

   Figure 2: The Registry Editor window that will pop-up

    

2. Find the DisableSelectiveSuspend key by clicking on HKEY_LOCAL_MACHINE, then click SYSTEM, CurrentControlSet, Services, and finally USB.
   
   NOTE: Your computer may not have the USB key. If you cannot find it at the location listed above you will need to create it. Follow the instructions below to do this. Otherwise continue to step 3.
   
   If it does not exist, first click the services folder, then click the Edit toolbar and click Edit>New>Key. Name it USB
   
   
   

   Figure 3: If the USB key does not exist under the 'services' folder create it by clicking on the 'services' folder and going to Edit>New>Key. Name this folder 'USB'

   Once the USB folder has been created, select it and right-click in the right hand screen area. Click New, and select DWORD (32-bit) Value. It may be named DWORD Value, depending on your computer. Name this value DisableSelectiveSuspend.
   
   
   

   Figure 4: Once the USB folder is created, right-click in the right hand window and select 'DWORD (32-bit) Value'

   

   Figure 5: Name the new value 'DisableSelectiveSuspend'

3. Once you have found or created the DisbaleSelectiveSuspend key in the USB folder, right click it and select Modify. In the ValueData field enter 1, and click OK.
   
   
   

   Figure 6: After right-clicking the DisableSelectiveSuspend key and clicking modify, enter 1 in the Value Data field. Click OK once this is done

4. The Selective Suspend feature is now disabled! Close out of the Registry Editor and restart your computer. Now try and connect the Gamry potentiostat.
   
   If the instrument still does not connect there may be a hardware issue. Contact Gamry Technical Support at 215-682-9330 or techsupport@gamry.com