Hi Fish,
Hold down the Reset Button then try to connect the MCU using JLink Commander. Release the Reset Button if you can establish a connection to target.
The KL04 only support SWD, please don't select JTAG.
For the hardware:
The RESET_b pin should have a 100 nF capacitor close to the MCU for transient protection. An external 4.7 kΩ to 10 kΩ pullup is recommended.
The NMI_b pin must not have any capacitance connected to it. An external 4.7 kΩ to 10 kΩ pullup is recommended.
SWD_DIO: an external 4.7 kΩ to 10 kΩ pullup is recommended.
SWD_CLK: float or an external 4.7 kΩ to 10 kΩ pulldown is recommended.
Best Regards,
Robin
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