As explained previously about what ESC bootloader does, we can use so called “1-wire” interface to flash and configure your ESC firmware settings.

Basically that means you can just plug your ESC signal and ground wire into your USB linker programmer, or Arduino board, and no need to rip apart the heatshrink to access the Atmel chip any more.

If you have SimonK Bootloader on the ESC already (safe to assume so if you already have SimonK Firmware on the ESC), you can use 1-wire flashing for both BLHeli and SimonK. If you have BLHeli Bootloader, you can only use 1-wire with BLHeli firmware.

Flashing ESC directly on the chip, using flash tool.