Flight Controller-F405 - Manual

BOTWING Flight Controller-F405 - Manual

About Botwing F405

Meet BotWing F405, the versatile flight controller that powers everything - from FPV racing and cinematic drone shoots to DIY learning projects. Built around the reliable STM32F405 MCU and the precision ICM42688P gyro, BotWing F405 offers smooth, stable flight performance across a wide range of setups. With support for Mission Planner, iNav, and BetaFlight, and a wide power input range (2S–6S LiPo), it’s designed to adapt seamlessly to your needs - whether you’re chasing racing flags or cinematic.

landscapes. The solderless design ensures clean, quick, and hassle- free assembly, making it ideal for builders at every experience level.

It features 4 motor outputs, integrated 32MB Blackbox logging, crisp AT7456E OSD display, plug-and-play DJI Air Unit compatibility, and a full suite of UARTs and LED strip.

Layout

Specification

DimensionsWW	40x40mm
Firmware	Mission Planner, iNav, BetaFlight
Firmware Target Name	BOTWINGF405
Mounting	30.5mm x 30.5mm (4mm hole size)
MicroController(MCU)	STM32F405
Motor Outputs	4 Motors
Gyro (IMU)	ICM42688P
Power Input	2S-6S LiPo
On Screen Display (OSD)	AT7456E
BlackBox	32 MB Winbond Blackbox
Buzzer	BZ+ and BZ- pad used for 5V Buzzer
i2C	i2C Supported SDA & SCL pads on front side. Used for magne-tometer , sonar etc.
ESC Telemetry UART	UART-2
RSSI	Named as RSSI on the front side
Boot Button	Supported, Press and hold BOOT button and power the FC on at the same time, this will force the FC to enter into DFU Mode, This is used for Firmware Flashing
Led Pads for LED STRIP	Led Pads for LED STRIP Sup-ported, 5V, GND, DATA pads are present on the top side.
Firmware Target Name	AM32_AT32PB4_540_F421
Weight	9gms
DJI AIR Unit-6-pin DJI Air Unit Plug	Plug and Play Port
UARTs	UART1(Radio), UART2(ESC), UART3(VTX), UART4(Camera), UART5, UART6(GPS) (6 Sets)
USB Port Type	Type-C
4.5V Pads	4 group of 4.5V pads is used
5V	5V pad 4 group of 5V Pads used in LED Strip, Total 5V Pads = 6
9V Pad	1 Pad is present
3.3V Pads	1 Pad is present
Camera Control Pad	Not Present

Package Include

Connections

Method 1 - Soldering

LED Indication

RED LED	5V and 3.3V
Blue LED	Status LED 1
Green LED	Status LED 2

LED Connection Options:

You can connect LEDs to the F405 flight controller in two ways:

1. Solder Pads: Use the dedicated 5V, GND, and Signal pads on the board.
2. 4-Pin Connector: Use the 4-pin LED connector which includes: 5V, GND, Signal In, and Signal Out.

Daisy Chain Functionality

1. By default, the LED connectors are daisy-chained, allowing each connector to control a separate LED strip independently.
2. If you want all connectors to control standard LEDs in parallel (same signal to all strips), follow these steps:

Parallel LED Setup Instructions

1. Cut the Signal Out wire on all connectors except the first one.
2. Bridge the small pad next to the signal pad on the flight controller for each modified connector.
3. This reroutes all connectors to share the same signal line from the first connector, enabling synchronized LED behavior.

Note: Perform this modification only on three connectors. The first connector already supplies the master signal.

Avoid Sbus or RX use with DJI or Vice versa

When integrating an ExpressLRS (ELRS) receiver with a DJI Air Unit (such as the O3, Link, Vista, or Air Unit V1), it’s crucial to manage the SBUS connections to prevent UART conflicts that can disrupt receiver functionality.

The DJI Air Unit’s 6-pin connector includes an SBUS (or DJI HDL) wire, typically yellow, intended for use with DJI’s own remote controllers. If you’re utilizing an ELRS receiver instead of a DJI remote, this SBUS wire becomes redundant and can interfere with the ELRS receiver’s operation by causing signal conflicts on the flight controller’s UART. (Oscar Liang).

To resolve this, carefully remove the SBUS wire from the DJI Air Unit’s connector. Use a fine tool, like a needle or tweezers, to gently lift the plastic tab securing the wire and slide it out of the connector. Once removed, insulate the exposed end with heat shrink tubing or electrical tape to prevent any potential short circuits. (Oscar Liang)

After disconnecting the SBUS wire, connect your ELRS receiver to an available UART on the flight controller, ensuring proper wiring of the TX and RX lines. In your flight controller’s configuration software (such as Betaflight), enable the corresponding UART for serial RX and set the receiver protocol to CRSF, which is compatible with ELRS.

By removing the unnecessary SBUS connection from the DJI Air Unit, you eliminate potential signal conflicts, allowing your ELRS receiver to function correctly and ensuring reliable control of your drone.