Pixracer¶

The Pixracer is the first autopilot of the FMUv4 Pixhawk generation. It comes with a small Wifi extension board.

Overview¶

The Pixracer is the common name for the FMUv4 generation of Pixhawk autopilots. It has been designed primarily for the demanding requirements of small multicopters, but of course can be used on planes and other vehicles which require no more than 6 pwm outputs for controlling escs and motors. Pixracer is available from the mRobotics

Tip

At time of writing the autopilot is still being evolved/improved. The final version may very slightly from the information provided here.

This video below provides a detailed overview of the board. Additional information can be found on pixhawk.org and the mRobotics.

Specifications¶

Processor:
- MCU - STM32F427VIT6 rev.3
- Ultra low noise LDOs for sensors and FMU
- FRAM - FM25V02-G
Sensors
- Gyro/Accelerometer: Invensense MPU9250 Accel / Gyro / Mag (4 KHz)
- Gyro/Accelerometer: Invensense ICM-20608 Accel / Gyro (4 KHz)
- Barometer: MS5611
- Compass: Honeywell HMC5983 magnetometer with temperature compensation
Power
- 5-5.5VDC from USB or PowerBrick connector. Optional/recommended ACSP4 +5V/+12V Power Supply.
Interfaces/Connectivity
- Wifi: ESP-01 802.11bgn Flashed with MavESP8266
- MicroSD card reader
- Micro USB
- RGB LED
- GPS (serial + I2C)
- TELEM1/TELEM2
- Wifi serial
- FrSky Telemetry serial(see note)
- Debug connector (serial + SWD)
- Connectors: GPS+I2C, RC-IN, PPM-IN, RSSI, SBus-IN, Spektrum-IN, USART3 (TxD, RxD, CTS, RTS), USART2 (TxD, RxD, CTS, RTS), FRSky-IN, FRSky-OUT, CAN, USART8 (TxD, RxD), ESP8266 (full set), SERVO1-SERVO6, USART7 (TxD, RxD), JTAG (SWDIO, SWCLK), POWER-BRICK (VDD, Voltage, Current, GND), BUZZER-LED_BUTTON.
Dimensions
- Weight ?
- 36 x 36mm with 30.5 x 30.5mm hole grid with 3.2mm holes

Note

The FrSky telemetry port is implemented using a 74LVC2G86 NOR gate as a programmable inverter to both the RX and TX lines. See below for use information.

Connector pin assignments¶

Unless noted otherwise all connectors are JST GH

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

This port has built in inverters on the TX and RX lines and shunt resistors which allow them to be tied together and connected to an FrSky receiver’s SPort input for telemetry. It is on by default, and only SERIAL4_PROTOCOL needs to be set to “10” for FrSky passthrough telemetry to be sent to the receiver. See FrSky Telemetry for more information.

The operation of the TX/RX path inverter can be disabled by setting the SERIAL4_OPTIONS parameter to “2” to “invert” the TX , which will turn off the inversion for both the TX and RX pins. This will allow normal UART operation, if desired.

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)	CURRENT	+3.3V
4 (blk)	BUZZER-	-
5 (blk)	BUZZER+	-

Debug port (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

Where to Buy¶

We suggest buying directly from mRobotics.
Whilst PixRacer can be sourced from other retailers, the specific design may differ and not have been tested by the Development Team. Known retailers of 3rd party PixRacer boards are HobbyKing, and Banggood, …