(DEV_TARGET_CMD_ERR) when trying to flash custom pcb with STM32WLE5J8I6

[Cvan .7]

Short and simple question: Why am I getting this error? Is there something obviously wrong with the schematic?

Tested all possible configurations when trying to connect. Holding boot, holding reset, nothing works. The error code changes to target not found when the supply is removed from the MCU.

All the voltages around the MCU on the capacitors are right. All capacitors are near the BGA. VDDPA is 1.5V, all VDD pins are 3.3V.

There is one thing which bothers me. The vref+ pin is not connected. The datasheet mentions this Pin to be connected to VDDA or Ground, nothing about a floating state. Is it impossible to flash the device when the vref+ pin is floating? Because this is the only problem i can find at the moment.

Note. I have access to an X-Ray and all the pins seem to be connected properly.

Thanks in advance.

[Cvan .7 · Accepted solution]

Solved

It was indeed the VREF+ pin. Removed the BGA, cut a little trench from VDDA to VREF+, added some conductive pen, put the BGA back on. And long behold, STM32CubeProgrammer can connect!