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Can not connect to J-Link via USB.

Applies to: uVision Debugger


Information in this knowledgebase article applies to:


I try to debug an ARM7/9 device with uVision Debugger via J-Link. But starting a debug session or a flash download always fails with the following message in the Build Output window:

Can not connect to J-Link via USB.


The J-Link device is probably configured for a J-Link USB ID other than 0. Due to that, it can't be recognized by the uVision J-Link Debugger driver used for ARM7/9 devices.


Configure the J-Link for USB ID 0. This can be done with the J-Link commander tool found in the MDK-ARM installation directory C:\Keil\ARM\Segger\JLink.exe. This will identify the J-Link with ID different than 0 and when connected, provides a command "usbaddr" to change the ID:

SEGGER J-Link Commander V4.36l ('?' for help)
Compiled Dec 2 2011 18:52:52
DLL version V4.40c, compiled Jan 24 2012 09:30:33
Firmware: J-Link ARM V6 compiled Feb 1 2011 14:28:14
Hardware: V6.00
S/N: ********
Feature(s): FlashBP, FlashDL
USB address successfully changed to '0'.
Please unplug the device, then plug it back in.

After reconnecting the J-Link unit to the PC, debugging the ARM7/9 device with J-Link via the uVision Debugger should work.

Please note that also the uVision J-Link Debugger driver used for Cortex-M devices has the ability to use J-Links with different USB ID and the ID can also be changed with J-Link Setup dialog.



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Article last edited on: 2012-08-20 07:45:23

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