# Specifications

**Mechanical Form Factor:**

* 71 x 49 x 23 mm (with case)
* 45g (with case)
* Standardized microUSB connector location
* Standardized RGB led location
* Standardized connector locations



**System architecture:**

FMUv4-PRO continues the PX4FMU+PX4IO architecture from the previous generation, incorporating the two functional blocks in a single physical module. \
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**I/O ports:**

* 6-14 PWM servo outputs (8 from IO, 6 from FMU).
* R/C inputs for CPPM, Spektrum / DSM and S.Bus.
* Analog / PWM RSSI input.
* S.Bus servo output.
* 6 general purpose serial ports, 2 with full flow control, 1 with separate 1A current limit, 1 with FrSky protocol inverter.
* Two I2C ports.
* Two external SPI ports (unbuffered, for short cables only).
* Two CAN Bus interfaces.
* Analog inputs for voltage / current of two batteries
* On-ground usage piezo buzzer driver.
* Sensor upgrade connector scheme
* High-power RGB LED.
* Safety switch / LED.



**PWM Outputs:**

Eight PWM outputs are connected to IO and can be controlled by IO directly via R/C input and onboard mixing even if FMU is not active (failsafe / manual mode). Multiple update rates can be supported on these outputs in three groups; one group of four and two groups of two. PWM signal rates up to 400Hz can be supported.

Six PWM outputs are connected to FMU and feature reduced update latency. These outputs cannot be controlled by IO in failsafe conditions. Multiple update rates can be supported on these outputs in two groups; one group of four and one group of two. PWM signal rates up to 400Hz can be supported.

All PWM outputs are ESD-protected, and they are designed to survive accidental mis-connection of servos without being damaged. The servo drivers are specified to drive a 50pF servo input load over 2m of 26AWG servo cable. PWM outputs can also be configured as individual GPIOs. Note that these are not high-power outputs – the PWM drivers are designed for driving servos and similar logic inputs only, not relays or LEDs. \
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**Peripheral Ports:**

FMUv4-PRO recommends separate connectors for each of the peripheral ports (with a few exceptions). This avoids the issues many users reported connecting to the 15-pin multi-IO port on the original PX4FMU-PRO and allows single-purpose peripheral cables to be manufactured.

Five serial ports are provided. TELEM 1, 2 and 3 feature full flow control. TELEM4 can be switched into inverted mode by hardware and has no flow control. Serial ports are 3.3V CMOS logic level, 5V tolerant, buffered and ESDprotected.

The SPI ports are not buffered; they should only be used with short cable runs. Signals are 3.3V CMOS logic level, but 5V tolerant.

Two power modules (voltage and current for each module) can be sampled by the main processor.

The RSSI input supports either PWM or analog RSSI. CPPM, S.Bus and DSM/ Spektrum share now a single port and are auto-detected in software.

The CAN ports are standard CAN Bus; termination for one end of the bus is fixed onboard. \
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**Sensors:**

The new **ICM-20602** has been positioned by Invensense as higher-end successor of the MPU-6000 series. The software also supports the MPU-9250, which allows a very cost-effective 9D solution.

Data-ready signals from all sensors (except the MS5611, which does not have one) are routed to separate interrupt and timer capture pins on FMU. This will permit precise time-stamping of sensor data.

The two external SPI buses and six associated chip select lines allow to add additional sensors and SPI-interfaced payload as needed.

**IMU is isolated from vibrations**.
