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GooSky F4 Mini

GooSky F4 Mini in an S2

A small Rotorflight flight controller, and a drop-in replacement for the stock flight controller in the GooSky S2 Max and S2 Ultra.
Board GOOSKY_F4MINI
MCU STM32F405
Gyro ICM-42688-P
Blackbox 128 MB flash (W25N01G)
Servo outputs 3 (1.25 mm micro JST, Molex PicoBlade compatible)
UARTs UART1 (ELRS / DSMX), UART2 (SBUS), UART5 (ESC telemetry)
Connectors 3-pin SBUS, 4-pin ELRS (1.25 mm), 3-pin DSMX (JST-ZH), 5-pin ESC (JST-PH: power, telemetry, main and tail motor)
Supply 5-16 V
Size, weight 24 × 33 × 9 mm, 12 g

It pairs with the GooSky 3S F421 2-in-1 ESC: two AT32F421 ESCs running AM32, with bidirectional DShot RPM for both motors and BLHeli32-format telemetry (voltage, current, temperature).

Setting up an S2 Max or S2 Ultra

1. Flash the F4 Mini

Flash the latest release with the GOOSKY_F4MINI board and Full chip erase.

2. Configure

Look for an S2 preset on the Presets tab, or set up the helicopter with the Setup Guides. Then:

  1. Calibrate the accelerometer.
  2. Centre the servos.
  3. Check the collective trim and zero pitch.
  4. Set up rates, modes and adjustments for your radio.

The Rotorflight 2.2 S2 tune

The team's S2 tune (headspeeds 4400 / 5100 / 5500 rpm) was made for Rotorflight 2.2: f4mini-s2-diff.txt. Use it for reference rather than loading it onto 2.3 or later, where the governor and rates have changed -- see the Upgrade Notes.

3. Update the ESC firmware

Warning

Follow this carefully. A failed flash can leave the ESC needing special tools to recover.

  1. Download the latest AM32_GOOSKY_3S_F421_<version>.hex from the AM32 releases.
  2. Power up the S2 and connect the F4 Mini by USB. Make sure the Rotorflight Configurator isn't connected.
  3. Open am32.ca/configurator, click Connect, then Read.
  4. Flash firmware → Local tab. The first time, tick Ignore current MCU layout. Choose the hex file and Start flash.

4. Configure the ESCs

ESC 1 drives the main motor, ESC 2 the tail. They need slightly different settings -- the main ESC mustn't brake on spool-down, while the tail ESC uses complementary PWM.

  1. In the AM32 Configurator, Apply config with s2-main-esc-config.bin, with only ESC 1 selected.
  2. Apply config with s2-tail-esc-config.bin, with only ESC 2 selected.
  3. Disconnect and power down.

In 2.4, the ESC Programming tab can also change AM32 settings per ESC.

Editing the tail ESC in the AM32 Configurator

The AM32 Configurator shows ESC 1's settings even when only ESC 2 is selected. To edit the tail ESC there, temporarily expose only the tail ESC from the Rotorflight CLI:

resource MOTOR 1 A08
resource MOTOR 2 NONE
save

and afterwards restore:

resource MOTOR 1 C08
resource MOTOR 2 A08
save

Check everything carefully, then go and fly.