SpeedyBee F405 V4
The SpeedyBee F405 V4 is a 30x30 (30.5 x 30.5 mm, 4 mm holes) STM32F405 flight controller. It is sold on its own and as the SpeedyBee F405 V4 BLS 55A 30x30 Stack together with the SpeedyBee BLS 55A 4-in-1 ESC. It has an onboard Bluetooth chip (for FC/ESC configuration via the SpeedyBee app), a MAX7456-compatible AT7456E analog OSD, a barometer, a microSD-card slot for Blackbox, and a 6-pin plug-and-play connector for DJI air units. The firmware target name is SPEEDYBEEF405V4.
- Specifications
- Wiring Diagrams
- Photos
- Notes
Target:
SPEEDYBEEF405V4
MCU:
STM32F405
IMU:
ICM42688P
OSD:
AT7456E
Baro:
DPS310
Blackbox:
SD Card
Measurements:
Size: 41.6 x 39.4 x 7.8 mm
Mounting: 30.5 x 30.5 mm (4 mm holes)
Weight: 10.5 g
Other Features
- SD Card Slot: Yes — SDSC/SDHC cards up to 32 GB, formatted FAT16/FAT32 (SDXC not supported)
- Onboard Receiver: None
- Hardware Inverter: No
- Bluetooth: Yes (BLE) — used for FC/ESC configuration via the SpeedyBee app; MSP on UART4 at 115200 baud
- WiFi: No
- Onboard RGB LED: None (4 corner WS2812 pads LED1–LED4, plus a status/battery LED array)
Input/Output
- USB Connector: USB Type-C
- Motor Outputs: 8x (M1–M4 via the 8-pin ESC connector / bottom pads, M5–M8 on front-side pads)
- UARTs: 6x (UART4 is dedicated to the onboard Bluetooth chip; UART5 is dedicated to ESC telemetry)
- I2C: Yes (for magnetometer, sonar, etc.)
- SWD: Yes
- SPI: Internal only (gyro on SPI1, OSD on SPI2, SD card on SPI3) — not broken out to user pads
- 3.3V Output: Yes — up to 500 mA (for 3.3V-input receivers)
- 4.5V (VBUS) Output: Yes — up to 1 A; powered even when running from USB (for RX/GPS)
- 5V Output: Yes — 3 A total across 9 groups (4x front 5V pads, BZ+, and 4x LED 5V pads)
- 9V Output: Yes — 3 A total across 2 groups (front 9V pad and the bottom DJI connector)
- Current Sensor: Yes (ESC-supplied) — reads current from the ESC via the 8-pin connector; for the SpeedyBee BLS 55A ESC use scale 400, offset 0
- Analog RSSI Input: Yes (RS pad)
- LED Strip Output: Yes (WS2812, LED pad)
- Buzzer Output: Yes (5V buzzer, BZ+ / BZ- pads)
Pads
UARTs
| Name | Label | Notes |
|---|---|---|
| UART 1 | T1 / R1 | Bottom edge; grouped with the analog VTX pads and used by the DJI 6-pin connector for OSD/air-unit MSP. |
| UART 2 | T2 / R2 | Top edge; also broken out as the SBUS pad (SBUS internally uses UART2). Default serial-RX / receiver UART. |
| UART 3 | T3 / R3 | Top edge. |
| UART 4 | — | No pads; dedicated to the onboard Bluetooth chip (MSP, 115200 baud). |
| UART 5 | R5 (TEL) | Only the RX pad (labelled TEL) is broken out; dedicated to ESC telemetry. The target defines only UART5 RX. |
| UART 6 | T6 / R6 | Bottom edge; grouped with 4V5 / SDA / SCL for GPS + compass. |
Power
| Name | Label | Notes |
|---|---|---|
| Battery Voltage | BAT | 3-6S LiPo input (also supplied via the 8-pin ESC connector). |
| 5V Output | 5V | 5V BEC, 3 A total across 9 groups. |
| 9V Output | 9V / VTX | 9V BEC, 3 A total; the VTX 9V rail is switchable via PINIO (Betaflight USER1). |
| 4.5V Output | 4V5 | 4.5V output, up to 1 A; live even over USB. |
| 3.3V Output | 3V3 | 3.3V output, up to 500 mA. |
Other
| Name | Label | Notes |
|---|---|---|
| Motors (front) | M5 – M8 | Front-side motor output pads (M5–M8). |
| Camera Video In | CAM | Analog FPV camera video input. |
| Camera Control | CC | Betaflight camera control. |
| RSSI | RS | Analog RSSI input. |
| Servo | S9 | Servo / extra PWM output. |
| LED Strip | LED | WS2812 addressable LED data. |
| I2C | SDA / SCL | Magnetometer, sonar, etc. |
| Buzzer | BZ+ / BZ- | 5V buzzer. |
Connectors
8-Pin ESC Connector (SH 1.0 mm)
Connects the FC to the ESC. Either end of the supplied cable can be used. FC-side pad definition (top to bottom):
| Pin | FC Label | ESC Label |
|---|---|---|
| 1 | GND | N/A |
| 2 | BAT | CURRENT |
| 3 | M1 | S4 |
| 4 | M2 | S3 |
| 5 | M3 | S2 |
| 6 | M4 | S1 |
| 7 | CUR | VBAT |
| 8 | TEL | GND |
DJI 6-Pin Air Unit Connector
Plug-and-play with DJI O3 / RunCam Link / Caddx Vista / DJI Air Unit V1. Board-side silkscreen labels:
| Pin | Label | Notes |
|---|---|---|
| 1 | 9V | VTX power (manufacturer cable diagrams label this pin 7.4-26.4V). |
| 2 | G | Ground. |
| 3 | T1 | UART1 TX (air-unit / OSD MSP). |
| 4 | R1 | UART1 RX (air-unit / OSD MSP). |
| 5 | G | Ground. |
| 6 | SBUS (R2) | Receiver SBUS passthrough (UART2 RX). |
- Manufacturer: SpeedyBee (LangTian Technology (Shenzhen) Co.) — speedybee.com.
- Product page: SpeedyBee F405 V4 BLS 55A 30x30 FC & ESC Stack.
- The OSD chip is an AT7456E, a MAX7456-compatible clone (the Betaflight target uses the
USE_MAX7456driver). - UART4 is not broken out to pads — it is wired to the onboard Bluetooth chip. Bluetooth configuration requires MSP enabled on UART4 at 115200 baud (the default).
- When using an SBUS receiver, connect its signal wire to the SBUS pad (UART2). If a DJI air unit is also connected via the 6-pin cable, remove/insulate the SBUS wire from the air-unit harness so the external SBUS receiver is recognised.
- ESC telemetry is on UART5 (RX-only, TEL pad).
- Blackbox: use SDSC or SDHC microSD cards up to 32 GB, formatted FAT16 or FAT32. SDXC cards are not supported.
- The four corner WS2812 pads (LED1–LED4) can be switched between Betaflight control (BF_LED) and SpeedyBee control (SB_LED) using the onboard BOOT button; default is BF_LED.
- To recover a bricked board, hold the BOOT button while plugging in USB to force DFU, then flash the
SPEEDYBEEF405V4target. - Firmware target:
SPEEDYBEEF405V4(Betaflight, INAV).