Esp32 serial port online upgrade

[rwj112358]

I wonder whether Esp32 could be upgraded by serial port online.I have learnt the esp-serial-flasher-master routine which finished by serial port offline from MCU.Now I need to finish the serial port online from STM32 to esp32 because the connection of STM32 and esp32 has been limit to two IO(rx and tx).I tried to reverse the OTA example,but it shows the error of "esp_ota_ops: OTA image has invalid magic byte (expected 0xE9, saw 0x00)" when I calls the esp_ota_write().
Following is my questions:
1.Whether the serial port online upgrade of ESP32 could be finished with OTA example?
2.IF there any other way of serial port online upgrade?(Beacuse of official recommand that the SPI flash operation functions:pation spi function should be used)


0;31mE (144899) esp_ota_ops: OTA image has invalid magic byte (expected 0xE9, saw 0x00)[0m

[0;31mE (146737) esp_image: image at 0x110000 has invalid magic byte[0m
[15:19:09.099] [0;33mW (146737) esp_image: image at 0x110000 has invalid SPI mode 255[0m
[15:19:09.099] [0;33mW (146741) esp_image: image at 0x110000 has invalid SPI size 15[0m