Connectors & Pinout
All board-to-wire connectors use JST-GH style. Pin 1 is marked on the connector housing.
Connector Overview
| Connector | Ref | Pins | Function |
|---|---|---|---|
| Power | CN1 | 6 | Main battery input |
| TELEM 1 | CN2 | 6 | Telemetry / MAVLink with flow control |
| TELEM 2 | CN3 | 6 | Telemetry / companion computer with flow control |
| Basic GPS | CN4 | 6 | GPS UART + I2C compass |
| CAN 1 | U18 | 4 | FDCAN1 bus |
| CAN 2 | U19 | 4 | FDCAN2 bus |
| External I2C | U20 | 4 | I2C expansion |
| External SPI | CN7 | 7 | SPI expansion |
| Motors | U21 | 12 | 8× motor outputs + ESC telemetry + current sense |
| VTX | CN6 | 6 | Video transmitter power and control |
| RC IN | U22 | 3 | RC receiver input |
| USB-C | USBC1 | — | USB 2.0 FS device / power |
The +5V pins on all connectors come from the board's 5 V rail. A load on them that varies substantially in flight (servos, companion computer, video transmitter) can throw off the onboard compass. For systems like that, use an external GPS + compass module. See Magnetometer.
Power — CN1
6-pin JST-GH. Main battery input.
| Pin | Signal |
|---|---|
| 1 | VBAT_IN |
| 2 | VBAT_IN |
| 3 | VBAT_IN |
| 4 | GND |
| 5 | GND |
| 6 | GND |
Pins 1–3 are paralleled for current capacity and lower contact resistance. Pins 4–6 are paralleled ground. This connector feeds the board's protected VBAT input (fuse → TVS → ideal-diode front end).
Input voltage: 2S–6S LiPo / Li-ion (approximately 7–25.2 V).
TELEM 1 — CN2
6-pin JST-GH. Primary telemetry port with hardware flow control.
| Pin | Signal | MCU |
|---|---|---|
| 1 | +5V | — |
| 2 | TM1_UART_TX | UART4 TX (PA0) |
| 3 | TM1_UART_RX | UART4 RX (PA1) |
| 4 | TM1_UART_CTS | UART4 CTS (PB0) |
| 5 | TM1_UART_RTS | UART4 RTS (PB14) |
| 6 | GND | — |
Default function: MAVLink (TEL1). Hardware flow control is supported. Enable via MAV_0_FLOW_CTRL in QGroundControl without a firmware rebuild.
TELEM 2 — CN3
6-pin JST-GH. Secondary telemetry port with hardware flow control.
| Pin | Signal | MCU |
|---|---|---|
| 1 | +5V | — |
| 2 | TM2_UART_TX | UART7 TX (PE8) |
| 3 | TM2_UART_RX | UART7 RX (PE7) |
| 4 | TM2_UART_CTS | UART7 CTS (PE10) |
| 5 | TM2_UART_RTS | UART7 RTS (PE9) |
| 6 | GND | — |
Default function: TEL2. Commonly used for companion computers. Hardware flow control enabled by default.
Basic GPS — CN4
6-pin JST-GH. UART GPS with I2C compass support.
| Pin | Signal | MCU |
|---|---|---|
| 1 | +5V | — |
| 2 | GPS_UART_TX | USART6 TX (PC6) |
| 3 | GPS_UART_RX | USART6 RX (PC7) |
| 4 | GPS_I2C_SCL | I2C4 SCL (PD12) |
| 5 | GPS_I2C_SDA | I2C4 SDA (PD13) |
| 6 | GND | — |
I2C lines are pulled up to 3.3 V on-board. Supports UART GPS modules with an integrated compass (connect compass via I2C4). Compatible with M8N, M9N, F9P, and similar modules using a standard 6-pin GPS cable.
This is a 6-pin port, not the full 10-pin Pixhawk GPS+safety-switch port. GPS modules that include a buzzer, safety switch, or LED typically use the 10-pin format and are not directly compatible.
CAN 1 — U18
4-pin JST-GH. FDCAN1 bus.
| Pin | Signal |
|---|---|
| 1 | +5V |
| 2 | CAN1_H |
| 3 | CAN1_L |
| 4 | GND |
The 305ap includes two 120 Ω termination resistors onboard for this port. The bus is fully terminated at the FC. Do not add any external termination resistors — doing so will lower bus impedance below spec and cause signal integrity issues.
CAN 2 — U19
4-pin JST-GH. FDCAN2 bus.
| Pin | Signal |
|---|---|
| 1 | +5V |
| 2 | CAN2_H |
| 3 | CAN2_L |
| 4 | GND |
Same termination applies: two 120 Ω resistors onboard, bus fully terminated at the FC. Do not add external terminators. See CANBUS for DroneCAN configuration.
External I2C — U20
4-pin JST-GH. General-purpose I2C expansion.
| Pin | Signal | MCU |
|---|---|---|
| 1 | +5V | — |
| 2 | EX_I2C_SCL | I2C2 SCL (PB10) |
| 3 | EX_I2C_SDA | I2C2 SDA (PB11) |
| 4 | GND | — |
Signal lines pulled up to 3.3 V on-board. I2C data is 3.3 V logic. Do not connect 5 V I2C devices without level shifting.
External SPI — CN7
7-pin JST-GH. SPI expansion with two chip selects.
| Pin | Signal | MCU |
|---|---|---|
| 1 | +5V | — |
| 2 | EX_SPI_SCK | SPI4 SCLK (PE2) |
| 3 | EX_SPI_MISO | SPI4 MISO (PE13) |
| 4 | EX_SPI_MOSI | SPI4 MOSI (PE6) |
| 5 | EX_SPI_CS1 | SPI4 CS1 (PC13) |
| 6 | EX_SPI_CS2 | SPI4 CS2 (PC14) |
| 7 | GND | — |
Motors — U21
12-pin connector. 8 motor outputs, ESC telemetry, and current sense.
| Pin | Signal | Notes |
|---|---|---|
| 1 | +5V | ESC logic / signal power |
| 2 | CURRENT_SENSE | Analog current input (0–3.3 V) — connect to ESC or power module current output |
| 3 | MOTOR_TELEM_RX | USART1 RX (PA9) — ESC serial telemetry (BLHeli32 / AM32) |
| 4 | MOTOR1 | TIM1 CH1 (PA8) |
| 5 | MOTOR2 | TIM1 CH2 (PE11) |
| 6 | MOTOR3 | TIM2 CH1 (PA15) |
| 7 | MOTOR4 | TIM2 CH3 (PA2) |
| 8 | MOTOR5 | TIM3 CH2 (PA7) |
| 9 | MOTOR6 | TIM3 CH4 (PB1) |
| 10 | MOTOR7 | TIM4 CH2 (PB7) |
| 11 | MOTOR8 | TIM4 CH3 (PD14) |
| 12 | GND | — |
Motor outputs support PWM, OneShot, and DSHOT. ESC telemetry (pin 3) is single-wire receive-only via USART1 SINGLEWIRE+SWAP mode.
VTX — CN6
6-pin JST-GH. Dedicated video transmitter power and control.
| Pin | Signal | Notes |
|---|---|---|
| 1 | +9V | Regulated from onboard AP63357 9 V buck, independent of 5 V rail |
| 2 | VTX_UART_TX | USART2 TX (PD5) — MSP DisplayPort OSD to VTX/goggles (default) |
| 3 | VTX_UART_RX | USART2 RX (PD6) |
| 4 | GND | — |
| 5 | VTX_SBUS | USART3 TX (PD8) — SBUS out (TX only; PD9 is the red LED) |
| 6 | GND | — |
The 9 V rail is available whenever the board is powered from battery. It is not available from USB power alone.
Stock firmware runs msp_osd on USART2 at 115200 baud (MSP_OSD_CONFIG=103, TELEM 3). Compatible goggles receive an OSD overlay as soon as the FC boots — no additional configuration needed. Note that the on-screen battery reading is average per-cell voltage, not pack voltage (3.7-3.8 V/cell is normal at rest).
RC IN — U22
3-pin. RC receiver input.
| Pin | Signal | Notes |
|---|---|---|
| 1 | +5V | Receiver power |
| 2 | RC_IN | UART5 (PB13) — SBUS, CRSF, PPM, or other single-wire protocol |
| 3 | GND | — |
Single-wire input via UART5 SINGLEWIRE+SWAP. CRSF and uninverted ELRS are fully supported. For SBUS, PX4 uses hardware UART inversion on the STM32H7. For CRSF/ELRS receivers that need a full-duplex UART, connect to TELEM 1 or TELEM 2 and reassign the port function in QGroundControl.
USB-C — USBC1
Standard USB-C receptacle. USB 2.0 Full Speed device.
| Signal | Notes |
|---|---|
| D+ / D− | USB 2.0 FS data (PA12 / PA11) |
| VBUS | Feeds 5 V power mux (TPS2116) — board can run from USB alone |
| CC1 / CC2 | 5.1 kΩ to GND — identifies board as a standard 5 V USB sink |
| GND / Shield | — |
ESD protection via USBLC6-4SC6. No USB Power Delivery. 5 V only. No VBUS detection line in firmware.