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Failed to initialize debug session / Emulation start failed


The error means that the debugger failed to connect to the target CPU. This can be for different reasons. 

When troubleshooting the initial debug connection to the target CPU, it is recommended to use the CPU Reset instead of Download.

Possible problems and solutions

BlueBox is not properly connected to the target debug connector


The necessary voltage is not connected to the target LPD debug connector or JTAG/Nexus debug connector

Refer to Setting debug interface voltage levels (Vref).  

BlueBox hardware can be damaged (Connector on the BlueBox, Debug Adapter, Active Probe)

Try to confirm this with another working BlueBox system. In case you confirm that the BlueBox hardware is damaged, contact technical support


If pins in connectors (in most cases pin 40 on ST1 connector) are bent, possible errors are: Error 250: FP5 Serial Communication error (Renesas RH850), DAP initialization failed (Infineon TriCore), CPU initialization failed (NXP/ST Power Architecture). 

The Target CPU can be damaged or permanently locked (e.g. by programming the wrong UCB data)

Try to test the BlueBox on another target or try to replace the CPU with a new one.

Active Watchdog prevents establishing a debug session

Disable all reset sources during debugging. See further explanation.

Incorrect JTAG Scan speed configuration

Open Hardware | CPU Options | JTAG  and configure the Scan speed.

Arm Cortex-M: Failed to initialize debug session

Infineon TriCore: Failed to initialize debug session / DAP Initialization failed
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