ChibiOS: add CIPHERWINGF4 (STM32F405) hwdef and bootloader

[jeevesh326]

Summary

Add CIPHERWINGF4 (STM32F405) ChibiOS hardware definition — a customized OmnibusF4-style flight controller supporting INAV, PX4, and ArduPilot firmware.

This board features optimized UART mapping, onboard OSD (MAX7456), and optional BMI270/ICM20689 IMU support.

---

Hardware Overview

Function	Pin	Notes
IMU (SPI1)	PA4 (CS), PA5 (SCK), PA6 (MISO), PA7 (MOSI)	Supports MPU6000 / BMI270 / ICM20689
Baro + OSD (SPI3)	PA15 (OSD CS), PB3 (BMP280 CS), PC10–PC12	MAX7456 OSD + BMP280
I2C1	PB8 (SCL), PB9 (SDA)	External compass / GPS
UART1	PA10 (RX), PA9 (TX)	CRSF / SBUS input
UART2	PA3 (RX), PA2 (TX)	Telemetry 1
UART3	PB11 (RX), PB10 (TX)	Telemetry 2
UART6	PC7 (RX), PC6 (TX)	GPS
USB	PA11 (DM), PA12 (DP)	OTG1 port
PWM Outputs	PB0–PB15, PA8	8 PWM outputs, DShot compatible
LED/Beeper	PB5 (LED), PB4 (Buzzer)	Status indicator & alarm
RSSI	PC1	Analog RSSI input
Battery	PC2 (Voltage), PC1 (Current)	Supports external current sensor

---

Notes

• Based on OmnibusF4 Pro reference design.
• No internal compass (I2C pads provided).
• Designed and tested by Jeevesh Vishwavijay Singh (CipherWing Labs).
• Supports INAV and PX4 unofficially, validated under ArduPilot build.

---

Files Added

• libraries/AP_HAL_ChibiOS/hwdef/CIPHERWINGF4/hwdef.dat
• libraries/AP_HAL_ChibiOS/hwdef/CIPHERWINGF4/hwdef-bl.dat
• libraries/AP_HAL_ChibiOS/hwdef/CIPHERWINGF4/README.md
• Tools/bootloaders/CIPHERWINGF4_bl.bin

---

Verification

• ✅ Bootloader built via Tools/scripts/build_bootloaders.py CIPHERWINGF4

• ✅ Firmware compiles successfully:
  Waf: Leaving directory '/home/jeevesh18/ardupilot/build/CIPHERWINGF4'
  'copter' finished successfully

• ✅ Tested with INAV & PX4 builds (non-official)

---

Future

This hardware is currently in student-stage development.
Planned for official CipherWing Labs release after validation.

[Hwurzburg]

The provided images really do not have a good enough silkscreen for each pads function to review, however a quick scan of the readme and hwdef, indicates that SBUS is notr supported...on an F4 it needs an timer interrupt input OR a separate pad that inverts SBUS before application to a UART setup with protocol 23 (and it should have full DMA to accommodate CRSF/ELRS RC in also). FYI, the UART protocol for SBUS is OUTPUT only, not input so cant be used for SBUS RCin.

[jeevesh326]

The provided images really do not have a good enough silkscreen for each pads function to review, however a quick scan of the readme and hwdef, indicates that SBUS is notr supported...on an F4 it needs an timer interrupt input OR a separate pad that inverts SBUS before application to a UART setup with protocol 23 (and it should have full DMA to accommodate CRSF/ELRS RC in also). FYI, the UART protocol for SBUS is OUTPUT only, not input so cant be used for SBUS RCin.

Added SBUS input support using a BSS138 inverter circuit connected to UART5_RX (PD2).
This allows proper signal inversion for SBUS input on the STM32F405 while maintaining UART1 and UART6 for telemetry or CRSF/ELRS.
• Updated hwdef.dat to define UART5_RX as inverted and set it as the default RC input port (HAL_RCIN_UART 5).
• Updated the board README to include SBUS hardware inverter details and RC input configuration.

The hardware schematic now includes an onboard BSS138 inverter between the SBUS pad and PD2.
This should resolve the SBUS compatibility concern mentioned earlier.

[jeevesh326]

✅ All checks have passed (56 successful).

I’ve addressed the previous SBUS inversion feedback by routing SBUS input through UART5_RX via BSS138 inverter, and confirmed successful ChibiOS and bootloader builds.

and i will update all the silkscreenlayer notation for pad and pins to be easier to understand

The board definition (CIPHERWINGF4) is stable and ready for final review.

@Hwurzburg @peterbarker — kindly review and approve when possible. Thank you for your guidance throughout this process!

[Hwurzburg]

@jeevesh326 when the new images are uploaded, I can review....ping me

[jeevesh326]

@jeevesh326 when the new images are uploaded, I can review....ping me

@Hwurzburg Please verify the pcb

[Hwurzburg]

the new silkscreen has not BAT- pads, only BAT+
the vtx and cam rows have no labels for pads
the LED row has + and - pads...what are they? + should have its voltage labeled, and what is -? gnd?
once these are answered I can review...thanks

[jeevesh326]

the new silkscreen has not BAT- pads, only BAT+

the vtx and cam rows have no labels for pads

the LED row has + and - pads...what are they? + should have its voltage labeled, and what is -? gnd?

once these are answered I can review...thanks

Hi @Hwurzburg
I’ve updated the silkscreen again to make things clearer. The VTX and CAM pads are not labeled on the top layer due to limited space, but I’ve added clear notations on the bottom silkscreen layer for reference.
Also, I’ve updated all “+” and “–” markings to directly show “+5V” and “GND” to avoid any confusion.

Thanks for the feedback — this should make it easier to identify everything now.

[jeevesh326]

you can check the user manual @Hwurzburg
end_manual.pdf

[Hwurzburg]

add and use that pinout image from the user manual to this PR, please....