mRo Pixracer (FMUv4)

:::warning PX4 does not manufacture this (or any) autopilot. Contact the manufacturer for hardware support or compliance issues. :::

The Pixhawk® XRacer board family is optimized for small racing quads and planes. In contrast to Pixfalcon and Pixhawk it has in-built WiFi, new sensors, convenient full servo headers, CAN and supports 2M flash.

:::tip This autopilot is supported by the PX4 maintenance and test teams. :::

Key Features

• Main System-on-Chip: STM32F427VIT6 rev.3

  • CPU: 180 MHz ARM Cortex® M4 with single-precision FPU

  • RAM: 256 KB SRAM (L1)

• Standard FPV form factor: 36x36 mm with standard 30.5 mm hole pattern

• Invensense® ICM-20608 Accel / Gyro (4 KHz) / MPU9250 Accel / Gyro / Mag (4 KHz)

• HMC5983 magnetometer with temperature compensation

• Measurement Specialties MS5611 barometer

• JST GH connectors

• microSD (logging)

• Futaba S.BUS and S.BUS2 / Spektrum DSM2 and DSMX / Graupner SUMD / PPM input / Yuneec ST24

• FrSky® telemetry port

• OneShot PWM out (configurable)

• Optional: Safety switch and buzzer

Where to Buy

Pixracer is available from the mRobotics.io.

Accessories include:

• Digital airspeed sensor

• Hobbyking® OSD + EU Telemetry (433 MHz)

Kit

The Pixracer is designed to use a separate avionics power supply. This is necessary to avoid current surges from motors or ESCs to flow back to the flight controller and disturb its delicate sensors.

• Power module (with voltage and current sensing)

• I2C splitter (supporting AUAV, Hobbyking and 3DR® peripherals)

• Cable kit for all common peripherals

Wifi (no USB required)

One of the main features of the board is its ability to use Wifi for flashing new firmware, system setup and in-flight telemetry. This frees it of the need of any desktop system.

• ESP8266 Wifi

• Custom ESP8266 MAVLink firmware

:::note Firmware upgrade is not yet enabled over WiFi (it is supported by the default bootloader but not yet enabled). Setup and telemetry are supported. :::

Assembly

See the Pixracer Wiring Quickstart

Wiring Diagrams

Grau setup pixracer top

:::note If using TELEM2 for an external telemetry module you will need to configure it as a MAVLink serial port. For more information see: Pixracer Wiring Quickstart > External Telemetry :::

Grau setup pixracer bottom

setup pixracer GPS

Grau b Pixracer FrSkyS.Port Connection

Grau ACSP4 2 roh

Grau ACSP5 roh

Connectors

All connectors follow the Pixhawk connector standard. Unless noted otherwise all connectors are JST GH.

Pinouts

Pixracer top pinouts

Pixracer bottom pinouts

Pixracer esp

TELEM1, TELEM2+OSD ports

Pin	Signal	Volt
1 (red)	VCC	+5V
2 (blk)	TX (OUT)	+3.3V
3 (blk)	RX (IN)	+3.3V
4 (blk)	CTS (IN)	+3.3V
5 (blk)	RTS (OUT)	+3.3V
6 (blk)	GND	GND

GPS port

Pin	Signal	Volt
1 (red)	VCC	+5V
2 (blk)	TX (OUT)	+3.3V
3 (blk)	RX (IN)	+3.3V
4 (blk)	I2C1 SCL	+3.3V
5 (blk)	I2C1 SDA	+3.3V
6 (blk)	GND	GND

FrSky Telemetry / SERIAL4

Pin	Signal	Volt
1 (red)	VCC	+5V
2 (blk)	TX (OUT)	+3.3V
3 (blk)	RX (IN)	+3.3V
4 (blk)	GND	GND

RC Input (accepts PPM / S.BUS / Spektrum / SUMD / ST24)

Pin	Signal	Volt
1 (red)	VCC	+5V
2 (blk)	RC IN	+3.3V
3 (blk)	RSSI IN	+3.3V
4 (blk)	VDD 3V3	+3.3V
5 (blk)	GND	GND

CAN

Pin	Signal	Volt
1 (red)	VCC	+5V
2 (blk)	CAN_H	+12V
3 (blk)	CAN_L	+12V
4 (blk)	GND	GND

POWER

Pin	Signal	Volt
1 (red)	VCC	+5V
2 (blk)	VCC	+5V
3 (blk)	CURRENT	+3.3V
4 (blk)	VOLTAGE	+3.3V
5 (blk)	GND	GND
6 (blk)	GND	GND

SWITCH

Pin	Signal	Volt
1 (red)	SAFETY	GND
2 (blk)	!IO_LED_SAFETY	GND
3 (blk)	VCC	+3.3V
4 (blk)	BUZZER-	-
5 (blk)	BUZZER+	-

Debug Port

The pinouts and connector comply with the Pixhawk Debug Mini interface defined in the Pixhawk Connector Standard (JST SM06B connector).

Pin	Signal	Volt
1 (red)	VCC TARGET SHIFT	+3.3V
2 (blk)	CONSOLE TX (OUT)	+3.3V
3 (blk)	CONSOLE RX (IN)	+3.3V
4 (blk)	SWDIO	+3.3V
5 (blk)	SWCLK	+3.3V
6 (blk)	GND	GND

For information about using this port see:

• SWD Debug Port

• PX4 System Console (Note, the FMU console maps to UART7).

Serial Port Mapping

UART	Device	Port
UART1	/dev/ttyS0	WiFi (ESP8266)
USART2	/dev/ttyS1	TELEM1 (flow control)
USART3	/dev/ttyS2	TELEM2 (flow control)
UART4
UART7	CONSOLE
UART8	SERIAL4

Schematics

The reference is provided as: Altium Design Files

The following PDF files are provided for convenience only:

• pixracer-rc12-12-06-2015-1330.pdf

• pixracer-r14.pdf - R14 or RC14 is printed next to the SDCard socket

Building Firmware

:::tip Most users will not need to build this firmware! It is pre-built and automatically installed by QGroundControl when appropriate hardware is connected. :::

To build PX4 for this target:

make px4_fmu-v4_default

Configuration

Compass calibration should be done with USB disconnected. This is always recommended, but is necessary on Pixracer because the USB connection produces particularly large levels of magnetic interference.

Configuration is otherwise the same as for other boards.

Credits

This design was created by Nick Arsov and Phillip Kocmoud and architected by Lorenz Meier, David Sidrane and Leonard Hall.