BLHeli_S configurator in your browser and on Android

BLHeli_S is the firmware that shipped on most 8-bit ESCs for small and mid-size quads: 4-in-1 boards on whoops, toothpicks and many 5-inch builds. It runs on SiLabs EFM8 microcontrollers, the EFM8BB1 and the faster EFM8BB2, and understands DShot as well as older analog protocols. Development ended with version 16.7, so any BLHeli_S ESC you buy today runs 16.7 or an earlier 16.x.

What BLHeli_S never got is bidirectional DShot, the RPM telemetry Betaflight's RPM filter uses. That is why many pilots move these ESCs to Bluejay, which runs on the same hardware. If that is your goal, the Bluejay configurator page walks through it. If you want to keep BLHeli_S and just tune it, this page covers every setting FlySpark changes.

Years ago, configuring BLHeli ESCs meant a separate USB linker clipped onto the signal wire. Today the flight controller does that job: Betaflight and INAV have a passthrough mode, the BLHeli 4-way interface, that bridges the USB port to every ESC's signal pad. FlySpark switches the flight controller into this mode when you open the ESC configurator, reads each ESC, and switches it back when you press Done.

The ESCs only answer when powered, so connect the flight battery after USB. Use DShot or Multishot as the motor protocol, keep the drone disarmed, and leave the CLI before opening the ESC screen. The flight controller pauses its normal MSP connection while you edit; FlySpark reconnects to it automatically afterwards.

Motor timing has five steps from Low to High. Higher timing suits high-KV motors but runs hotter; Medium is the usual starting point. Demag compensation, Off, Low or High, helps prevent desyncs on hard throttle punches, the stutter or sudden motor stop you sometimes hear on aggressive flying. If a motor desyncs, raising demag is one of the first things to try.

Startup power sets how hard the ESC pushes to start the motor, from 0.031 to 1.50. Raise it only if motors stutter on startup. Low RPM power protection limits power at low RPM; the BLHeli_S manual notes it may need to be off to reach full power with low-KV motors on low voltage. Temperature protection cuts power above a threshold from 80 to 140 °C, or can be turned off.

Brake on stop actively holds the motor when the throttle is at zero. Beep strength sets how loud the ESC beeps, beacon strength sets the volume of the lost-model beacon, and beacon delay sets how long the quad must sit still before the beacon starts: 1, 2, 5 or 10 minutes, or never. Motor direction offers normal, reversed, bidirectional (3D) and bidirectional reversed.

BLHeli_S files are published per layout, such as A_H_15_REV16_7.HEX, in the BLHeli repository. FlySpark reads each ESC's layout and fetches the matching file, so a mixed set of ESCs gets the right file each. Flashing works on EFM8BB1 and EFM8BB2 ESCs and never touches the ESC's bootloader. The settings shared by the old and new firmware are written back afterwards.

Reflashing 16.7 is useful after an ESC was flashed with the wrong layout, after a failed flash, or to return from Bluejay. Before it starts, FlySpark writes **FLASH*FAILED** into the ESC's name field and points the reset address at the bootloader, and it erases the settings page last. If the flash is interrupted, the ESC starts in its bootloader, normally still reports its layout, and can be flashed again; the name tells other tools too that the flash did not finish.

Older ESCs ran the original BLHeli, version 14 and earlier. On Atmel ATmega chips it keeps its settings in EEPROM, and FlySpark reads and edits the fields that mean the same in every BLHeli 14 multirotor build: direction (normal, reversed or bidirectional), timing, demag, startup power, temperature protection on or off, low RPM protection, brake on stop and the beep settings. Only the bytes you changed are written.

Old BLHeli on SiLabs F-series chips stores its settings in a place that differs per chip, so those ESCs are identified by chip but not edited. FlySpark does not flash firmware to Atmel or SiLabs F-series ESCs.