This flashes Zephyr at 0x1000: that's where the first stage bootloader,
part of the ESP32 ROM, expects to find an "image header".
The second-stage bootloader, part of ESP-IDF, isn't used by the Zephyr
port. However, the bootloader can be used if desired; please refer to
the ESP-IDF documentation on how to set up partitions tables and use
the bootloader.
The following environment variables will affect the ESP32 flashing
process:
Variable Default value
ESP_DEVICE /dev/ttyUSB0
ESP_BAUD_RATE 921600
ESP_FLASH_SIZE detect
ESP_FLASH_FREQ 40m
ESP_FLASH_MODE dio
ESP_TOOL espidf
It's impossible to determine which serial port the ESP32 board is
connected to, as it uses a generic RS232-USB converter. The default of
/dev/ttyUSB0 is provided as that's often the assigned name on a Linux
machine without any other such converters.
The baud rate of 921600bps is recommended. If experiencing issues when
flashing, try halving the value a few times (460800, 230400, 115200,
etc). It might be necessary to change the flash frequency or the flash
mode; please refer to the esptool documentation for guidance on these
settings.
If ${ESP_TOOL} is set to "espidf", the esptool.py script found within
ESP-IDF will be used. Otherwise, this variable is handled as a path to
the tool.
Signed-off-by: Leandro Pereira <leandro.pereira@intel.com>
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