Board Layout
Form Factor
The 305ap is a 36.5 mm × 36.5 mm board with an M4 mounting hole pattern designed around soft-mount vibration isolation. Each mounting hole accepts a standard M3 rubber vibration isolator (M4 outer diameter, M3 inner bore) so the FC floats on rubber rather than bolting rigidly to the frame. Weight is 11 g with microSD card installed.
Connector Placement
The 305ap connector layout is designed for clean wire routing in a typical FPV stack:
| Connector | Location | Function |
|---|---|---|
| USB-C | Side edge | USB 2.0 FS programming and GCS connection |
| Motors | Bottom | 8× PWM/DSHOT outputs + ESC telemetry + current sense |
| TELEM1 | Side/top | 6-pin JST-GH, UART4 with CTS/RTS |
| TELEM2 | Side/top | 6-pin JST-GH, UART7 with CTS/RTS |
| GPS | Side | 6-pin JST-GH, USART6 + I2C4 |
| CAN1 | Side | 4-pin JST-GH, FDCAN1 |
| CAN2 | Side | 4-pin JST-GH, FDCAN2 |
| RC IN | Side | 3-pin, single-wire (SBUS/CRSF/PPM) |
| VTX | Side | 6-pin JST-GH, 9 V + UART2 + SBUS out |
| External I2C | Side | 4-pin JST-GH |
| External SPI | Side | 7-pin JST-GH |
| microSD | Bottom | Push-push slot, card detect supported |
Top Side
- STM32H743VIH6 MCU (TFBGA100)
- 2× IMU slots (SPI2, SPI3) — ST LSM6DSV or TDK InvenSense ICM-45686, auto-detected at boot
- BMP581 barometer (SPI)
- MMC5983MA magnetometer (I2C, internal)
- SIT1044T CAN transceivers
- Status LEDs (red, green, blue)
- BOOT and RESET buttons
Bottom Side
- Power components (AP63357 buck converters, LM74700-Q1, TPS2116, RT9193 LDO)
- RGB LED
- Motor output connector (U21)
- Voltage/current sense frontend (TLV9002)
- SMAJ30CA TVS, AON7246E FET
- microSD slot
Mounting
The 305ap uses a 36.5 mm × 36.5 mm mounting pattern with M4 mounting holes sized for standard M3 rubber vibration isolators. Each hole accepts one isolator (M4 OD × M3 ID) that the mounting M3 fastener passes through — the FC ends up floating on rubber with no direct metal-to-metal contact between the board and the airframe.
The mounting holes are electrically connected to GND — this is only relevant if the M3 screw contacts the frame directly. When using rubber isolators as intended, the rubber breaks the electrical path.
The board is a single-MCU architecture with no FMU/I/O split. All outputs and peripherals are driven directly by the STM32H743.
Fastener recommendations
- Use M3 screws through the isolators into standoffs on the frame side.
- Tighten M3 fasteners until snug, then back off a quarter turn — over-torquing crushes the isolator and defeats vibration isolation. The FC should have a small amount of visible give under finger pressure.
- Rubber anti-vibration isolators (M3 hardware inside an M4 outer body) are available from Avian Automata as a 12-pack replacement; four are included with each 305ap for a full first-install.
The M4 mounting hole pattern exists specifically to accept M3 rubber vibration isolators. Do not bolt the 305ap directly to the frame with M4 screws through the mounting holes — you lose the vibration isolation the mount was designed for. Every current-generation IMU is only as good as its mount, and hard-mounting transmits motor and airframe vibration straight into the gyro and accelerometer.
Buttons
| Button | Function |
|---|---|
| BOOT | Hold at power-on to enter DFU bootloader mode |
| RESET | Hard reset the MCU |
To enter DFU mode for flashing: hold BOOT, apply power (or press RESET while powered), then release BOOT. The board will enumerate as a DFU device over USB.
LEDs
See Troubleshooting → LED Status for a full LED code reference.
| LED | GPIO | PX4 Function |
|---|---|---|
| Red | PD9 | Errors, boot state |
| Green | PB12 | GPS lock, armed state |
| Blue | PE12 | Flight mode indicator |
| RGB | — | Full status (arming, modes, errors) |
Active-low: GPIO LOW = LED on.