NRA24 CAN Terrain-Following Radar Integration with CUAV X7+ and ArduPilot V4.6.2

27 Aug

NRA24 CAN Terrain-Following Radar Integration with CUAV X7+ and ArduPilot V4.6.2

Introduction

The NRA24 CAN radar is designed for UAV applications such as radar altimetry, terrain following, low-altitude flight, and altitude measurement. To verify its compatibility with modern flight control systems, we conducted an integration test using a CUAV X7+ flight controller running ArduPilot V4.6.2.

This test used a customized/recent NRA24 radar firmware:

Test_NRA24x200_SigPro_F303_DroneCAN_V1.0.4_20250929.hex

The test configuration was designed to verify that the NRA24 CAN radar can operate simultaneously with a CAN-based GPS module and provide rangefinder data to the flight controller.

In the test system, the NEO3 Pro GPS module was connected to CAN1, while the NRA24 CAN terrain-following radar was connected to CAN2.

Important: The CAN parameters in this article are based on the actual integration test performed with the specific NRA24 firmware listed above. They should not be considered universal parameters for every NRA24 firmware version.

1. Test Equipment and Configuration

The main hardware and software used in the integration test were:

Item	Test Configuration
Radar	NRA24 CAN Radar
Radar Application	Terrain Following / Radar Altimeter
Radar Firmware	`Test_NRA24x200_SigPro_F303_DroneCAN_V1.0.4_20250929.hex`
Flight Controller	CUAV X7+
Flight Controller Firmware	ArduPilot V4.6.2
Ground Control Station	Mission Planner
GPS Module	CUAV NEO3 Pro
GPS Interface	CAN1
Radar Interface	CAN2
CAN Bitrate	1 Mbps (1,000,000 bps)
Radar Detection Direction	Downward

The purpose of using CAN2 for the NRA24 radar was practical: the CAN1 interface of the X7+ was already occupied by the NEO3 Pro GPS module.

The resulting system architecture was:

                    NEO3 Pro GPS
                         │
                         │ CAN1
                         ▼
                 ┌─────────────────┐
                 │    CUAV X7+     │
                 │ Flight Controller│
                 │                 │
                 │ CAN1 ← GPS      │
                 │ CAN2 ← NRA24    │
                 └────────┬────────┘
                          │
                          │ CAN2
                          ▼
                   NRA24 CAN Radar
                          │
                          ▼
                Terrain Following /
                  Radar Altimeter

This configuration represents a practical UAV installation where multiple CAN devices need to operate simultaneously.

2. NRA24 CAN Radar Firmware

The NRA24 radar used in this test was loaded with:

Test_NRA24x200_SigPro_F303_DroneCAN_V1.0.4_20250929.hex

This firmware is designed to support CAN-based integration with flight controllers, including ArduPilot and PX4 platforms.

Because CAN communication parameters can vary between firmware versions, the firmware version should always be confirmed before configuring the flight controller.

For this test firmware, the confirmed CAN communication speed is:

CAN Bitrate: 1,000,000 bps

or:

1 Mbps

500 kbps is not applicable to this specific test firmware.

Customers should therefore use the CAN bitrate specified for the corresponding NRA24 firmware version rather than copying parameters from other NRA24 firmware releases or generic online examples.

3. ArduPilot and Mission Planner Configuration

The following configuration was tested with:

CUAV X7+
ArduPilot V4.6.2
Mission Planner
NRA24 V1.0.4
NRA24 connected to CAN2

3.1 CAN2 DroneCAN Configuration

Configure the CAN2 interface as follows:

Parameter	Value	Description
`CAN_D2_PROTOCOL`	1	Select DroneCAN communication protocol
`CAN_P2_DRIVER`	2	Enable/select the CAN driver used by CAN2
`CAN_P2_BITRATE`	1000000	CAN2 bitrate: 1 Mbps
`CAN_SLCAN_SERNUM`	0	Select USB virtual serial port for DroneCAN forwarding
`CAN_SLCAN_TIMEOUT`	2	DroneCAN forwarding-port communication timeout: 2 seconds

The most important CAN configuration is:

CAN_D2_PROTOCOL  = 1
CAN_P2_DRIVER    = 2
CAN_P2_BITRATE   = 1000000

After changing CAN parameters, reboot the flight controller so that the CAN configuration can take effect.

4. Rangefinder Configuration

The NRA24 radar is configured as a rangefinder in ArduPilot.

For the DroneCAN configuration used in this test:

RNGFND1_TYPE = 24

The corresponding parameters are:

Parameter	Value	Description
`RNGFND1_TYPE`	24	Select radar/rangefinder supporting DroneCAN
`RNGFND1_MIN_CM`	Application dependent	Minimum detection distance accepted by the flight controller
`RNGFND1_MAX_CM`	Application dependent	Maximum detection distance accepted by the flight controller

The minimum and maximum values should be selected according to the actual radar operating range and UAV application.

For example, if the radar is used as a downward-facing terrain-following sensor, the configured range should cover the expected operating altitude while remaining within the valid measurement range of the radar.

5. Radar Detection Direction

For terrain-following applications, the NRA24 radar should normally be installed facing downward.

The corresponding ArduPilot orientation parameter used in the test configuration is:

RNGFND1_ORIENT = 25

This configures the rangefinder detection direction as downward.

The physical installation of the radar is equally important. The radar should be securely mounted and aligned with the intended measurement direction.

An incorrect installation angle may cause the measured distance to differ from the actual vertical height above the terrain, especially when the UAV is flying over slopes or uneven terrain.

6. Complete ArduPilot CAN2 Parameter Example

For quick reference, the main test parameters are:

CAN_D2_PROTOCOL  = 1
CAN_P2_DRIVER    = 2
CAN_P2_BITRATE   = 1000000

CAN_SLCAN_SERNUM = 0
CAN_SLCAN_TIMEOUT = 2

RNGFND1_TYPE     = 24
RNGFND1_MIN_CM   = Application dependent
RNGFND1_MAX_CM   = Application dependent

The test system can be summarized as:

CUAV X7+
│
├── CAN1
│    └── NEO3 Pro GPS
│
└── CAN2
     └── NRA24 CAN Radar
          │
          └── 1 Mbps

This configuration allows the GPS and radar to operate through separate CAN interfaces on the same flight controller.

7. Why CAN2 Was Used for the NRA24 Radar

The use of CAN2 in this test was not a limitation of the NRA24 radar.

The reason was that the CAN1 interface was already being used by the NEO3 Pro GPS module.

Therefore, CAN2 was used for the NRA24 radar:

CAN1 → NEO3 Pro GPS

CAN2 → NRA24 CAN Radar

This configuration provides a useful reference for UAV developers who need to integrate several CAN devices into a single flight controller.

In practical UAV systems, CAN interfaces may be shared among GPS modules, rangefinders, airspeed sensors, ESCs, compasses, and other peripherals. Testing the NRA24 on CAN2 therefore provides a more realistic multi-device integration scenario than testing the radar alone.

8. Terrain-Following Application

The NRA24 radar can be used as a downward-looking rangefinder for UAV terrain-following applications.

The basic measurement process is:

             UAV
              │
              │
              ▼
       ┌─────────────┐
       │    NRA24    │
       │    Radar    │
       └──────┬──────┘
              │
              │ Radar measurement
              ▼
       Ground / Terrain

The radar continuously measures the distance between the UAV and the ground.

The flight controller can then use the rangefinder measurement together with other navigation and altitude information.

A typical terrain-following control chain is:

NRA24 Radar
     │
     │ CAN / DroneCAN
     ▼
CUAV X7+
     │
     │ Rangefinder Data
     ▼
ArduPilot
     │
     ├── Altitude Estimation
     ├── Terrain Following
     └── Flight Control

The actual behavior of terrain following depends on the flight controller configuration, flight mode, terrain data, EKF configuration, and other navigation sensors.

9. ArduPilot CAN1 and CAN2 Integration Options

The NRA24 firmware tested in this project can be used in different CAN integration configurations.

For the NanoRadar CAN communication method, the configuration uses:

CAN_Dx_PROTOCOL = 14
RNGFNDx_TYPE    = 39

For the DroneCAN configuration tested on the CUAV X7+, the configuration uses:

CAN_D2_PROTOCOL = 1
RNGFND1_TYPE    = 24

These two configurations should not be mixed.

The correct parameter set depends on the communication protocol being used by the radar and the corresponding flight-controller driver.

10. Firmware Version Is Important

CAN communication parameters should always be associated with the radar firmware version.

For this test:

Radar firmware:

Test_NRA24x200_SigPro_F303_DroneCAN_V1.0.4_20250929.hex

Flight controller:

CUAV X7+

ArduPilot:

V4.6.2

CAN bitrate:

1 Mbps

These parameters represent the actual tested configuration.

Different NRA24 firmware versions may use different CAN communication parameters, message definitions, supported protocols, or default measurement ranges.

Therefore, before performing an integration test, verify:

NRA24 firmware version
CAN communication protocol
CAN bitrate
Radar ID / Node ID
Rangefinder type
Minimum detection range
Maximum detection range
Radar orientation
Flight controller firmware version

11. Troubleshooting

Radar Is Not Detected

Check the following:

Verify that the NRA24 radar is powered correctly.
Confirm CAN-H and CAN-L wiring.
Confirm the CAN termination configuration.
Confirm the CAN bitrate is 1 Mbps for the tested V1.0.4 firmware.
Check CAN_D2_PROTOCOL.
Check CAN_P2_DRIVER.
Check the radar ID / Node ID.
Reboot the flight controller after changing CAN parameters.

Radar Data Is Unstable

Check:

Radar mounting stability
Radar detection direction
CAN wiring quality
Power supply stability
CAN bus termination
Electromagnetic interference
Radar operating environment
Configured minimum and maximum measurement ranges

Radar Measures the Wrong Height

First check the mechanical installation angle.

A terrain-following radar should normally be mounted vertically downward. If the radar is tilted, the measured distance is the slant distance rather than the true vertical distance.

12. ArduPilot Test Configuration Summary

The complete test environment can be summarized as follows:

Category	Configuration
Radar	NRA24 CAN
Radar Firmware	`Test_NRA24x200_SigPro_F303_DroneCAN_V1.0.4_20250929.hex`
Flight Controller	CUAV X7+
ArduPilot	V4.6.2
GCS	Mission Planner
CAN1	NEO3 Pro GPS
CAN2	NRA24 CAN Radar
CAN2 Protocol	DroneCAN
CAN2 Bitrate	1 Mbps
Rangefinder Type	24
Radar Orientation	Downward
Application	Terrain Following / Radar Altimeter

Conclusion

The integration test demonstrates the use of the NRA24 CAN radar with a CUAV X7+ flight controller running ArduPilot V4.6.2.

In this test configuration, the NEO3 Pro GPS occupied CAN1, while the NRA24 terrain-following radar was connected to CAN2. The NRA24 radar operated at a 1 Mbps CAN bitrate using the tested firmware Test_NRA24x200_SigPro_F303_DroneCAN_V1.0.4_20250929.hex.

This configuration provides a practical reference for UAV developers integrating NRA24 radar into ArduPilot-based flight-control systems.

The NRA24 firmware is also intended for integration with PX4-based flight controllers, providing a path for developers who require CAN/DroneCAN radar integration across different UAV autopilot platforms.

Firmware and parameter note: The parameters in this article are based on the actual NRA24 V1.0.4 integration test described above. Do not substitute CAN parameters from other NRA24 firmware versions without verifying firmware compatibility first.