pi@Lenovo-Linux:~ $ esptool.py --port /dev/ttyUSB0 erase_flash
esptool.py v2.2
Connecting.....
Detecting chip type... ESP32
Chip is ESP32D0WDQ6 (revision 0)
Uploading stub...
Running stub...
Stub running...
Erasing flash (this may take a while)...
Chip erase completed successfully in 4.0s
Hard resetting...
pi@Lenovo-Linux:~ $ esptool.py --chip esp32 --port /dev/ttyUSB0 write_flash -z 0x1000 esp32-20180111-v1.9.3-240-ga275cb0f.bin
esptool.py v2.2
Connecting.....
Chip is ESP32D0WDQ6 (revision 0)
Uploading stub...
Running stub...
Stub running...
Configuring flash size...
Auto-detected Flash size: 4MB
Compressed 935888 bytes to 587153...
Wrote 935888 bytes (587153 compressed) at 0x00001000 in 51.9 seconds (effective 144.4 kbit/s)...
Hash of data verified.

Leaving...
Hard resetting...
pi@Lenovo-Linux:~ $ ampy --help
Usage: ampy [OPTIONS] COMMAND [ARGS]...

  ampy - Adafruit MicroPython Tool

  Ampy is a tool to control MicroPython boards over a serial connection.
  Using ampy you can manipulate files on the board's internal filesystem and
  even run scripts.

Options:
  -p, --port PORT    Name of serial port for connected board.  Can optionally
                     specify with AMPY_PORT environemnt variable.  [required]
  -b, --baud BAUD    Baud rate for the serial connection (default 115200).
                     Can optionally specify with AMPY_BAUD environment
                     variable.
  -d, --delay DELAY  Delay in seconds before entering RAW MODE (default 0).
                     Can optionally specify with AMPY_DELAY environment
                     variable.
  --version          Show the version and exit.
  --help             Show this message and exit.

Commands:
  get    Retrieve a file from the board.
  ls     List contents of a directory on the board.
  mkdir  Create a directory on the board.
  put    Put a file or folder and its contents on the...
  reset  Perform soft reset/reboot of the board.
  rm     Remove a file from the board.
  rmdir  Forcefully remove a folder and all its...
  run    Run a script and print its output.
pi@Lenovo-Linux:~ $ ampy -p /dev/ttyUSB0 ls
b'\x02\x02`\x0e\xeer\xec'
Traceback (most recent call last):
  File "/usr/local/bin/ampy", line 11, in <module>
    sys.exit(cli())
  File "/home/pi/.local/lib/python3.5/site-packages/click/core.py", line 722, in __call__
    return self.main(*args, **kwargs)
  File "/home/pi/.local/lib/python3.5/site-packages/click/core.py", line 697, in main
    rv = self.invoke(ctx)
  File "/home/pi/.local/lib/python3.5/site-packages/click/core.py", line 1066, in invoke
    return _process_result(sub_ctx.command.invoke(sub_ctx))
  File "/home/pi/.local/lib/python3.5/site-packages/click/core.py", line 895, in invoke
    return ctx.invoke(self.callback, **ctx.params)
  File "/home/pi/.local/lib/python3.5/site-packages/click/core.py", line 535, in invoke
    return callback(*args, **kwargs)
  File "/home/pi/.local/lib/python3.5/site-packages/ampy/cli.py", line 147, in ls
    for f in board_files.ls(directory):
  File "/home/pi/.local/lib/python3.5/site-packages/ampy/files.py", line 94, in ls
    self._pyboard.enter_raw_repl()
  File "/home/pi/.local/lib/python3.5/site-packages/ampy/pyboard.py", line 192, in enter_raw_repl
    raise PyboardError('could not enter raw repl')
ampy.pyboard.PyboardError: could not enter raw repl