STLink error (16): AP wait with NUCLEO-L452RE board

Hello,

when I try to flash a NUCLEO-L452RE board with pyOCD i get a
STLink error (16): AP wait
When I compile the same mbed blinky project for an STM32L152 pyOCD flashes a NUCLEO-L152RE Board without a problem.

• Updated the ST-Link Programmer on the NUCLEO-Board to the latest version.
• I can flash both boards with openOCD and mbed cli tools.
• I have the same problem on a Windows 10 machine and a Mac running Big Sur.
• Board is directly connected via USB (no hubs in between).
• I also installed both packs for stm32l152 and stm32l452
• pyOCD reports version number 0.32.3

Command

pyocd flash --target stm32l452retx --erase=chip -0 connect_mode=under-reset mbed-20220208-2.bin

This is the terminal output:

0002880:ERROR:ap:Transfer error while reading AHB-AP#0 ROM table: STLink error (16): AP wait
Traceback (most recent call last):
  File ".../pyocd/coresight/ap.py", line 740, in find_components
    cmpid.read_id_registers()
  File ".../pyocd/coresight/rom_table.py", line 114, in read_id_registers
    regs = self.ap.read_memory_block32(self.top_address + self.IDR_READ_START, self.IDR_READ_COUNT)
  File ".../pyocd/probe/stlink_probe.py", line 270, in read_memory_block32
    return conversion.byte_list_to_u32le_list(self._link.read_mem32(addr, size * 4, self._apsel))
  File ".../pyocd/probe/stlink/stlink.py", line 385, in read_mem32
    return self._read_mem(addr, size, Commands.JTAG_READMEM_32BIT, self.MAXIMUM_TRANSFER_SIZE, apsel)
  File ".../pyocd/probe/stlink/stlink.py", line 345, in _read_mem
    raise self._ERROR_CLASSES[status](error_message)
pyocd.core.exceptions.TransferTimeoutError: STLink error (16): AP wait
0002883:CRITICAL:__main__:No cores were discovered!
Traceback (most recent call last):
  File ".../pyocd/__main__.py", line 150, in run
    status = cmd.invoke()
  File ".../pyocd/subcommands/load_cmd.py", line 96, in invoke
    with session:
  File ".../pyocd/core/session.py", line 341, in __enter__
    self.open()
  File ".../pyocd/core/session.py", line 459, in open
    self._board.init()
  File ".../pyocd/board/board.py", line 99, in init
    self.target.init()
  File ".../pyocd/core/soc_target.py", line 117, in init
    seq.invoke()
  File ".../pyocd/utility/sequencer.py", line 208, in invoke
    resultSequence = call()
  File ".../pyocd/coresight/coresight_target.py", line 247, in check_for_cores
    raise exceptions.DebugError("No cores were discovered!")
pyocd.core.exceptions.DebugError: No cores were discovered!

I also looked at #1147 but a power down problem can not be related to mine. Board is running/idle not power down.

Any pointers to what I could check or test would be appreciated.

Stephen

Reproduce the failure with the reported pyocd flash command and compare it with the working STM32L152 case. Start in pyocd/probe/stlink_probe.py and pyocd/probe/stlink/stlink.py, then trace the AP discovery path through coresight/ap.py and rom_table.py. Done means identifying the cause of the AP wait error and confirming a fix or a documented device limitation.