8.2 KiB
Pixracer Flight Controller
The Pixracer flight controller is sold by mRobotics
The full schematics of the board are available here:
https://github.com/ArduPilot/Schematics/tree/master/mRobotics
Features
- STM32F427 microcontroller
- MPU9250 and ICM20608 IMUs
- MS5611 SPI barometer
- builtin HMC5843 and MPU9250 magnetometers
- microSD card slot
- 6 UARTs plus USB
- 6 PWM outputs
- I2C and CAN ports
- Spektrum satellite cable
- External Buzzer
- builtin RGB LEDs
- external safety Switch
- voltage monitoring for Vcc
- dedicated power input port for external power brick
Pinout
UART Mapping
- SERIAL0 -> USB
- SERIAL1 -> UART2 (Telem1)
- SERIAL2 -> UART3 (Telem2)
- SERIAL3 -> UART4 (GPS)
- SERIAL4 -> UART8 (GPS2, FrSky Telem)
- SERIAL5 -> UART1 (spare)
- SERIAL6 -> UART7 (spare, debug port)
The Telem1 and Telem2 ports have RTS/CTS pins, the other UARTs do not have RTS/CTS.
Connectors
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
This UART is inverted by default. You can disable the inverter by setting SERIAL4_OPTIONS=2 if you want to use it with a non-inverted protocol.
| 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 all RC protocols)
| 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)
Note that in ArduPilot the debug UART is available as a general purpose UART.
| 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 |
RC Input
RC input is via a RC input cable. That cable comes in two forms, one for Spektrum satellite receivers and another for all other receiver types.
Both cables support all protocols with ArduPilot, but you need to use the Spektrum cable if you want to be able to bind the receiver using the ArduPilot binding support as only the Spektrum cable gives ArduPilot the ability to control the power on the Spektrum satellite receiver.
FrSky Telemetry
FrSky Telemetry is supported using SERIAL4, on the port marked as FrSky. You need to set the following parameters to enable support for FrSky S.PORT. You also need to cross-connect the TX and RX pins by creating a cable that connects both the TX and RX pins of the FrSky port to the FrSky S.Port pin on your receiver.
- SERIAL4_PROTOCOL 10
- SERIAL4_OPTIONS 0
PWM Output
The Pixracer supports up to 6 PWM outputs. All 6 outputs can support DShot as well as all PWM protocols.
The 6 PWM outputs are in 2 groups:
- PWM 1, 2, 3 and 4 in group1
- PWM 5 and 6 in group2
Channels within the same group need to use the same output rate. If any channel in a group uses DShot then all channels in the group need to use DShot.
Battery Monitoring
The board has a dedicated power monitor port on a 6 pin connector. The correct battery setting parameters are dependent on the type of power brick which is connected.
Compass
The Pixracer has two builtin compasses. One is a HMC5843 and the other is a part of the MPU9250 IMU. Due to potential interference the board is usually used with an external I2C compass as part of a GPS/Compass combination.
GPIOs
The 6 PWM ports can be used as GPIOs (relays, buttons, RPM etc). To use them you need to limit the number of these pins that is used for PWM by setting the BRD_PWM_COUNT to a number less than 6. For example if you set BRD_PWM_COUNT to 4 then PWM5 and PWM6 will be available for use as GPIOs.
The numbering of the GPIOs for PIN variables in ArduPilot is:
- PWM1 50
- PWM2 51
- PWM3 52
- PWM4 53
- PWM5 54
- PWM6 55
Analog inputs
The Pixracer has 4 analog inputs
- ADC Pin2 -> Battery Voltage
- ADC Pin3 -> Battery Current Sensor
- ADC Pin4 -> Vdd 5V supply sense
- ADC Pin11 -> Analog RSSI Input
Loading Firmware
The board comes pre-installed with an ArduPilot compatible bootloader, allowing the loading of *.apj firmware files with any ArduPilot compatible ground station.
Acknowledgements
Thanks to mRobotics and the PX4 project for images