https://www.rototron.info/raspberry-pi-esp32-micropython-tutorial
https://boneskull.com/micropython-on-esp32-part-1
LoBo's MicroPython for ESP32 with psRAM support

• Ensure venv is installed:
  $ sudo apt-get install python3-venv

• Create a python virtual env for esp32-related work:
  $ python3 -m venv pyvenv_esp32

• Active the venv:
  $ source pyvenv_esp32/bin/activate
  Note: To deactivate it later, type deactivate<enter> at the command prompt.

• Ensure using latest version of pip:
  $ python -m pip install pip --upgrade

• Install ESPTool:
  $ python -m pip install esptool

• Install rshell:
  $ python -m pip install rshell

• Determine serial port:
  $ dmesg --follow
  Watch the dmesg output as you plug in the USB cable. You should see a new device attached, e.g. ttyUSB0.

• Ensure board is working, using the ESPTool flash_id command:
  $ esptool.py --port /dev/ttyUSB0 flash_id
  If get a "Permission denied" error on the port (e.g. /dev/ttyUSB0), then may need to add your user to the group that the device is using.
  $ ls -l /dev/ttyUSB0
  For example, it might show /dev/ttyUSB0 assigned to the "dialout" group.
  Show the groups your user belongs to:
  $ groups userName
  If "dialout" isn't in the list, then add it:
  $ sudo usermod -a -G dialout userName
  Log out and log back in (might actually need to reboot) to see the new group added.

• First erase the flash:
  $ esptool.py --chip esp32 --port /dev/ttyUSB0 erase_flash

• Get the firmware from LoBo's repo.

  • Extract the firmware zip file to a "firmware" folder, which will contain, among other files, the flash.sh utility as well as a subfolder with a MicroPython.bin file (and other bin files).
  • Change your working directory to the folder with the MicroPython.bin file. The flash.sh script should be in its parent folder.

• Flash the firmware, using the flash.sh utility:
  $ ../flash.sh -p <comm_port> -b <baud_rate>
  Note that the -p and -b options are optional. The default port is /dev/ttyUSB0. The default baud rate is 460800.

  • Might need to hard reset the device after flashing.

• Start rshell
  $ rshell --port /dev/ttyUSB0

• Show the connected boards
  > boards

• Enter the python REPL
  > repl

  • Once in the repl, type help() to show intro help for MicroPython.
  • Exit the REPL with Ctrl-X