USB
Hardware
The 305ap uses a USB-C connector wired as a USB 2.0 Full Speed device.
| Signal | Pin | Notes |
|---|---|---|
| D+ | PA12 | USB OTG FS data+ |
| D− | PA11 | USB OTG FS data− |
| VBUS | 5V_USB_IN | Powers 5 V supply via TPS2116 mux |
| CC1 | — | 5.1 kΩ pulldown to GND |
| CC2 | — | 5.1 kΩ pulldown to GND |
ESD protection is provided by an ST USBLC6-4SC6, a very-low-capacitance protector rated for USB 2.0 high-speed interfaces with ~3 pF typical line capacitance.
USB 2.0 FS Only
This is a USB 2.0 Full Speed (12 Mbps) device port. High-speed (480 Mbps) is not supported. For PX4 ground station connectivity and firmware flashing, FS is entirely sufficient.
There is no USB Power Delivery controller. The 5.1 kΩ CC pulldown resistors identify the board as a USB sink (UFP), telling the host to supply standard 5 V. No PD negotiation occurs.
Power Behavior
VBUS from the USB connector feeds the TPS2116 power mux alongside the onboard 5 V switcher. The mux selects whichever rail is higher and supplies it to the +5V_BOARD net. This means:
- USB only (no battery): the board powers from USB. All sensors and peripherals come up normally. PWM outputs may not reach operating voltage.
- Battery + USB connected: the onboard 5 V switcher typically wins the mux and powers the board. USB VBUS is present but not driving any load.
There is no VBUS detection line. The firmware cannot sense whether USB power is present, so the board behaves identically regardless of USB connection state.
Connecting to QGroundControl
- Connect the 305ap to a host PC via a USB-C cable that supports data (not charge-only)
- QGroundControl will detect the board automatically and show a green link indicator
- On Linux:
sudo usermod -aG dialout $USER(then log out and back in) to allow non-root USB access
Firmware Flashing
USB is used for both DFU (bootloader) and QGC over-the-air firmware flashing. See Flashing for details.
MAVLink over USB
The USB port exposes a serial device (/dev/ttyACM0 on Linux, COM port on Windows) that carries MAVLink. QGC connects to this automatically. The default MAVLink instance on USB is separate from the telemetry radios on UART4/UART7.