Specifications
Karu has the full sensor set revision 3 (FMU, VMU) of the Pixhawk v6X-RT standard.
Processor and memory
| Part | Specification |
|---|---|
| Processor | NXP i.MX RT1176 : Arm Cortex-M7 at 1 GHz, Cortex-M4 at 400 MHz |
| Memory | 2 MB RAM, 64 MB external flash |
| Secure element | NXP EdgeLock SE052F : CC EAL 6+, IEC 62443-4-2, FIPS 140-3 |
The secure element stores keys and verifies that the firmware is authentic. PX4 reaches it through a driver module.
Sensors
| Sensor | Part |
|---|---|
| IMU | two ICM-45686 , one BMI088 |
| Barometer | two BMP390 |
| Magnetometer | BMM350 |
The three IMUs are in separate domains, each with its own bus and its own power control, so a failed sensor cannot stop the other two. Mechanical isolation inside the module damps the high-frequency vibration that spoils attitude estimation on a noisy airframe.
Running one estimator per IMU is in Sensors and redundancy .
Buses and addresses
The module contains two boards: the FMU board with the processor, and the IMU board on its mechanical isolation. The baseboard has the secure element and the NFC antenna connector. The table lists every onboard device on a sensor bus. I2C addresses are 7-bit.
| Device | Part | Board | Bus | Address or chip select |
|---|---|---|---|---|
| IMU 1 | ICM-45686 | FMU board | SPI1 | CS0, data ready DRDY1 |
| IMU 2 | ICM-45686 | IMU board | SPI2 | CS0, data ready DRDY1 |
| IMU 3, accelerometer | BMI088 | IMU board | SPI3 | CS0 |
| IMU 3, gyroscope | BMI088 | IMU board | SPI3 | CS1, data ready DRDY2 |
| Barometer 1 | BMP390 | FMU board | I2C2 | 0x76 |
| Barometer 2 | BMP390 | IMU board | I2C3 | 0x77 |
| Magnetometer | BMM350 | IMU board | I2C3 | 0x14 |
| Secure element | SE052F | baseboard | I2C6 | 0x48 |
| EEPROM | 24LC64 | IMU board | I2C3 | 0x50 |
| EEPROM | 24LC64 | baseboard | I2C6 | 0x51 |
I2C3 is internal to the module. I2C2 and I2C6 also go to baseboard ports, so an external
device on them must not use an address in this table; the
I2C buses
table lists the ports. PX4 numbers the buses the same way:
-b 3 is I2C3 and -b 1 on an SPI driver is SPI1.
Interfaces
The module meets the Pixhawk Autopilot Bus on the 100-pin and 50-pin connectors to the baseboard. The baseboard brings out the following. Pin tables and bus assignments are in Baseboard ports .
| Interface | Ports | Detail |
|---|---|---|
| Power input | 2 | POWER1 and POWER2, each with its own I2C bus for the power module’s monitor |
| PWM output | 12 | outputs 1 to 8 also do DShot |
| Serial | 4 | TELEM1, TELEM2 and TELEM3 with hardware flow control, TELEM1 on its own 5 V rail; UART & I2C adds I2C6 and a GPIO line for an external NFC reader |
| GNSS | 2 | GPS1 with compass I2C, safety switch and buzzer; GPS2 with compass I2C |
| CAN | 3 | three independent buses |
| Ethernet | 1 | 100BASE-T1 at 100 Mbit/s over one twisted pair, transformerless |
| SPI | 1 | two chip selects, two data-ready lines, sync and reset |
| I2C | 1 | I2C6, the bus the UART & I2C port also uses |
| RC input | 1 | SBUS or PPM on RC IN / AUX position 2, or Spektrum on DSM RC ; position 1 outputs SBUS |
| Analogue and IO | 1 | two analogue inputs, a PWM capture input, bootloader, reset and armed lines |
| Debug | 1 | console and SWD |
| USB | 1 | USB-C, with a header of the same signals beside it |
| NFC | 1 | antenna coil for the secure element |
Electrical
| Input | Range |
|---|---|
| POWER1, POWER2, USB | 4.8 to 5.4 V, 6 V absolute maximum |
| Servo rail | 0 to 10 V |
The 5 V rails that feed the ports have their own limits, see Peripheral rails .