FlyCore Electrical Integration Guide

This document is an installation, electrical connection, and commissioning guide for the FlyCore integrated control system, intended for OEM manufacturers, industrial UAV integrators, and secondary-development teams.

Safety Precautions and Operator Qualification Requirements (Required Reading)

This guide covers the soldering and measurement of high-voltage propulsion batteries (>24V), high-current circuits (>10A), and precision surface-mount components. Before performing any electrical integration work, the following safety and qualification requirements must be strictly observed.

Required Instruments and Tools

Before starting formal work, prepare and verify the following instruments. Do not perform any electrical connection or soldering if any one of these items is missing:

Non-Negotiable Operator Qualification Requirements

• Unqualified personnel must not perform these operations: Anyone performing electrical soldering, power distribution board wiring, or battery BMS hardware modifications (surface-mount work in Figure 1-3) must have basic analog circuit knowledge (including the ability to identify pull-up and pull-down resistors, voltage-divider principles, and common-ground interference) and practical experience soldering surface-mount components.
• Do not work on energized equipment: Before plugging or unplugging Dupont wires, soldering/removing series resistors, or measuring continuity with the resistance mode of a multimeter, ensure that the entire system is completely powered off (disconnect the propulsion battery and wait for the onboard capacitors of FlyCore-FC to discharge; waiting ≥30 seconds is recommended).
• High-voltage isolation awareness: If ADC battery adaptation mode is selected, the propulsion battery voltage (for example, approximately 25.2V for a 6S battery) must never be connected directly to an MCU pin. The integrator must independently design and verify an external voltage-divider/filter circuit to ensure that the ADC input voltage is ≤3.3V (the standard MCU ADC voltage tolerance). The integrator is responsible for any chip damage caused by direct high-voltage input.

Overview

The objective of the electrical system integration stage is to turn FlyCore from “usable as a standalone board” into “electrically reliable as a complete system.” It is recommended to proceed in the order of the power supply system first, the communication system next, and the sensor and propulsion loops last. This avoids moving directly into flight commissioning when the power supply is unstable or the communication links have not yet been verified.

Figure 1-1: Recommended overall electrical topology for the UAV system. Red lines indicate power flow, and blue lines indicate communication flow.

Power Supply System

Power Supply Requirements

The onboard computers must be isolated using DC-DC converters

Because the downstream side of a UAV system contains many capacitive and inductive loads, a spike far above the input voltage is generated at the instant power is applied and can easily damage the power module. The onboard computers should therefore not be connected directly to the raw propulsion battery voltage.

The recommended architecture is:

Figure 1-2: Isolated power supply topology for the onboard computers.

The DC-DC module does more than step down the voltage. It also isolates voltage spikes from the propulsion system, suppresses ESC switching noise, and reduces the effect of high-current battery fluctuations on the onboard computers and flight controller. During installation, measure the DC-DC output before connecting FlyCore-U and FlyCore-FC.

External Power Output Capacity

The FlyCore platform provides commonly used peripheral power outputs suitable for lightweight mission payloads, sensors, data-link core boards, and debugging accessories. A power budget must be prepared during integration to prevent either a single output or the combined power from exceeding the platform's capacity.

Integration principle: High-power mission payloads should use an independent regulated power supply. Long-term use of the FlyCore onboard external power reserve is not recommended.

Battery Adaptation

The carrier board's battery communication hardware supports three modes: CAN, IIC, and ADC. The 0Ω series resistor for CAN communication is installed by default, while the 0Ω series resistors for IIC communication and ADC acquisition are not installed by default. Components for the three modes must not be installed at the same time. Before using IIC or ADC, first complete the hardware modification for the target mode and confirm that the CAN path is no longer conducting.

Soldering and power-on inspection sequence:

• Power off the complete system, disconnect the propulsion battery, and confirm that no residual external power is supplied to FlyCore-FC.

• Select one of CAN, IIC, or ADC as the battery status mode according to the battery/BMS output method. Exactly one of the three component configurations must be used.

• Refer to Figure 1-3 to locate the 0Ω series-resistor pads inside the corresponding colored box: blue for CAN, yellow for IIC, and red for ADC.

• Install only the 0Ω series resistor corresponding to the target mode. If changing from the default CAN mode to IIC or ADC, confirm that the CAN path has been disconnected.

• After soldering, use a multimeter to verify that the target path is conducting, that the other two mode paths are not conducting, and that there are no short circuits between adjacent pads.

• For the ADC solution, the battery voltage must first be divided and filtered externally. Confirm that the ADC input voltage is within the allowable range of the MCU pin. Never connect the raw propulsion battery voltage directly to the ADC.

• Connect the battery status lines only after confirming that the hardware has been configured for exactly one of the three modes.

• After the hardware passes inspection, open the QGC Power page to calibrate the voltage/current and configure low-voltage protection.

The following three methods for acquiring battery level information are mutually exclusive. Only one component path may be selected in the field.

Figure 1-3: Diagram of the FlyCore-FC power-monitoring soldering locations. The blue box contains the 0Ω series resistor for CAN communication, the yellow box contains the 0Ω series resistor for IIC communication, and the red box contains the 0Ω series resistor for ADC acquisition.

CAN Battery Adaptation

Figure 1-4: CAN battery level information acquisition topology. Retain only the 0Ω series resistor in the blue box; the IIC and ADC paths must not conduct.

Precautions

CAN is suitable for connecting smart batteries, DroneCAN ESCs, or scalable energy management modules. During integration, pay particular attention to the following:

CAN_H/CAN_L must be routed as a pair and kept away from motor phase wires and the main battery cables.

Configure termination resistors at both ends of the bus as required by the devices, and avoid redundant termination at multiple points.

After connecting a smart battery, confirm in the ground station that the flight controller can recognize its voltage, current, remaining capacity, and alarm status.

If the same CAN bus carries both ESC and battery information, confirm that the node IDs and message bandwidth do not conflict.

IIC Battery Adaptation

Figure 1-5: IIC battery level information acquisition topology. Retain only the 0Ω series resistor in the yellow box; the CAN and ADC paths must not conduct.

Precautions

IIC is suitable for short-distance, low-speed status acquisition within or between boards, such as battery metering, temperature, or low-speed sensors. During integration, pay particular attention to the following:

IIC cables should not be routed over long distances across the arms.

SDA/SCL must use matching logic levels and pull-up strategies to avoid multiple modules providing strong pull-ups in parallel.

IIC devices must share a common ground with the flight controller. If cables pass near high-power areas, add shielding or use CAN/UART instead.

ADC Battery Adaptation

Figure 1-6: ADC battery level information acquisition topology. Retain only the 0Ω series resistor in the red box; the CAN and IIC paths must not conduct, and external voltage division/filtering must be implemented before the ADC.

Precautions

ADC is suitable for acquiring the battery voltage, current sensor output, or divided analog signals. During integration, pay particular attention to the following:

The propulsion battery signal must pass through voltage division/filtering before it is connected to the ADC. Never apply high voltage directly to the sampling input.

An isolated Hall-effect sensor or dedicated current-sensing module is recommended for current measurement.

After completing the hardware connection, calibrate the voltage and current scaling in QGC and verify low-voltage protection operation.

After completing the hardware mode configuration and wiring, first confirm in QGC that FlyCore-FC can correctly read the battery level information. Then, follow the flight control system user manual to configure multi-level low-voltage protection on the QGC Power page:

Sample Power Distribution Board

The sample power distribution board is a reference design that ROBOSN will release as open source to help users understand the recommended power-supply relationships among FlyCore-U, FlyCore-FC, and the propulsion system. The materials are provided for engineering reference and do not require users to adopt the same power distribution board. Users can redesign the PCB based on their own airframe, payload power consumption, and wiring-harness layout.

The reference power distribution board should cover three types of responsibilities: high-power distribution, low-power voltage regulation, and signal routing.

Figure 1-7: Power supply and protection topology of the ROBOSN open-source sample power distribution board.

When designing a power distribution board, users are advised to focus on the following design boundaries:

Communication System

System Communication Topology

The communication topology in this section is based on the system integration topology in Figure 1-1 and only provides further detail on the communication links, protocol types, and debugging entry points.

Figure 1-8: FlyCore recommended communication system topology

Key IP Addresses and Port Definitions

Connection Between the Onboard Computers and Flight Controller (Connection Between the Brain and Cerebellum)

In the FlyCore architecture:

• Brain: FlyCore-U, which contains the perception and positioning onboard computer and the RK3588 recognition, planning, and control onboard computer. It is responsible for mapping, positioning, recognition, planning, and application logic.

• Cerebellum: The FlyCore-FC flight controller, which is responsible for attitude control, actuator output, remote-control takeover, failsafe protection, and safety strategies.

At least two types of connections must be established between FlyCore-U and FlyCore-FC: a control link and a perception link. The control link is used for upper-level planning, mission control, and status feedback. The perception link delivers pose information such as fused positioning/VIO to FlyCore-FC as a data source for flight-controller-side position estimation and navigation control.

Figure 1-9: Front interfaces of FlyCore-U

Figure 1-10: FlyCore-FC interface diagram

Wiring requirements:

• FlyCore-U and FlyCore-FC must share a reliable common GND.

• The serial port connected on the FlyCore-FC side must be configured through QGC to ensure that its parameters are correct.

• The perception link uses a fixed 8N1@115200 configuration. The control link can be selected according to the user's implementation, but a rate above 921600 is not recommended.

• FlyCore-U Interface ⑩ is used for serial communication between the recognition, planning, and control onboard computer and FlyCore-FC. Verify the TX/RX crossover and pin order during wiring.

• FlyCore-U Interface ⑤ is used for serial communication between the perception and positioning onboard computer and FlyCore-FC. Verify the TX/RX crossover and pin order during wiring.

• Serial wiring should be kept away from the main battery cables, ESC wires, motor phase wires, and high-power copper areas of the PDB. Shielding and strain relief are recommended for long-distance wiring.

Highly Integrated Video and Data Transmission Module

FlyCore-FC provides a reserved BTB interface for video and data transmission. Users can design a video and data transmission module based on this interface to meet the video and data transmission requirements of UAVs in different scenarios. As shown in the figure, this interface is located beneath the flight controller expansion board (TELEM-MODULE_V1.0).

Its interface definition is shown below:

Users can independently design and develop a highly integrated video and data transmission module according to their actual requirements and structural size constraints. ROBOSN will also soon release a highly integrated video and data transmission module based on the LQ-10.