• I realized that I was still using 0018000902-AI03 firmware, so I decided to update it. I made a mistake of doing it on Windows because esptool.py kept timing out. Then I read about --no-stub option and added that to my command. Reading/writing started to work, but got slower and slower and timed out before reaching even 20% of flashing. I finally realized that I could have flashed it through Raspberry Pi 3+, but even there it doesn't work without --no-stub and flashing fails anyways. Whats my options?

    pi@raspberrypi:~ $ python -m esptool -p /dev/ttyACM0 -b 115200 --no-stub read_mac
    esptool.py v2.8
    Serial port /dev/ttyACM0
    Connecting...
    Detecting chip type... ESP8266
    Chip is ESP8266EX
    Features: WiFi
    Crystal is 26MHz
    MAC: 18:fe:34:9d:53:13
    Enabling default SPI flash mode...
    MAC: 18:fe:34:9d:53:13
    Hard resetting via RTS pin...
    
    pi@raspberrypi:~ $ python -m esptool -p /dev/ttyACM0 -b 115200 --no-stub write_flash 0 ESP8266_AT25-SDK112-512k.bin
    esptool.py v2.8
    Serial port /dev/ttyACM0
    Connecting...
    Detecting chip type... ESP8266
    Chip is ESP8266EX
    Features: WiFi
    Crystal is 26MHz
    MAC: 18:fe:34:9d:53:13
    Enabling default SPI flash mode...
    Configuring flash size...
    Auto-detected Flash size: 512KB
    Erasing flash...
    Took 1.05s to erase flash block
    Writing at 0x00000000... (0 %)
    A fatal error occurred: Invalid head of packet (0x13)
    
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