Unable to identify the nrf5340 chip through the swd interface.

[valerian123]

I made a PCB board, but I couldn't connect to the chip with JLink. I used a lithium battery to power VDDH. I want to test if there is any problem with the hardware. I tried to measure the voltages of several regulators: VDDNRF = 1.8V, DECR = 1.09V, DECD = 1.106V, DECA = 1.245V, DECN = 1.0V. But I don't know what they should be under normal circumstances. I'm not sure if it's a hardware issue.

[Ressa]

Hi, 

You need to provide the debugger with a target voltage reference (VTref/VTG) from the nRF5340’s VDD rail, even when the board is battery-powered. The J-Link will only enable its SWD level shifters when it senses this voltage, and the logic levels must match the target’s VDD. Connect VTref (VTG) on the debugger to the board’s VDD, also ensure common GND. Do not feed 5 V (or battery voltage) into VTref. VTref should reflect the actual SoC VDD (typically ~1.7–3.6 V).

Best regards,
Ressa