HLK-LD2450: A C++ repository from RBEGamer

LD2450 24Ghz Human Radar

Arduino library for HLK-LD2450 24Ghz Human body Motion Inductive Radar Sensor Module Kit

An Arduino library for the Hi-Link HLK-LD2450 24Ghz FMCW radar sensor. This sensor is a Frequency Modulated Continuous Wave radar, which makes it good for presence detection and has some interesting new features, including precise target location of three objects at the same time.

HARDWARE REQUIREMENTS

The LD2450, as sold for configuration with the common breakout boards shown above communicates over serial at 256000 baud by default. This library allows you to configure and use the sensor over this serial connection. As the LD2450 is a device that uses a high baud rate, a microcontroller with a spare hardware UART for this communication is preferable to bit-banged software serial.

API

    void begin(Stream &radarStream);
    void begin(SoftwareSerial &radarStream, bool already_initialized = false); // compile with #define ENABLE_SOFTWARESERIAL_SUPPORT
    void begin(HardwareSerial &radarStream, bool already_initialized = false); // setup sensor with given Hardware Serial instance such as Serial1
    void setNumberOfTargets(uint16_t _numTargets); // how many targets should be parsed - limit is three on current ld2450 firmware
    RadarTarget getTarget(uint16_t _target_id); // get a target by number from 0 - getSensorSupportedTargetCount()
    uint16_t getSensorSupportedTargetCount();
    String getLastTargetMessage(); // get debug message - see basic example
    uint8_t read(); // handle serial data stream, must be called in loop
    bool waitForSensorMessage(bool wait_forever = false); // checks if the radar sensors sends data, waits for an valid incomming datastream usinf the read function

The RadarTarget struct, contains all raw values returned from the sensor:

    typedef struct RadarTarget
    {
        uint16_t id;             // TARGET ID 1-3
        int16_t x;               // X mm
        int16_t y;               // Y mm
        int16_t speed;           // cm/s
        uint16_t resolution;     // mm
        uint16_t distance;       // mm
        bool valid;              // TRUE IF TARGET DETECTED
    } RadarTarget_t;

In the current sensors firmware state (at least on my board), the LD2450 always returns three targets. The current implementation extracts the valid flag by using the resolution field. If resolution is set to an value except than 0, the target is marked asvalid and detected. For more information about this specific implementation, please refer to ProcessSerialDataIntoRadarData function.

MINIMAL EXAMPLE

WIRING

LD2450	RASPBERRY PI PICO
5V	VBUS
GND	GND
TX	GPIO1 / GP1
RX	GPIO0 / GP0

ARDUINO IDE SETUP

Add the Raspberry Pi Pico board support to the Arduino IDE:

Raspberry Pi Pico/RP2040 by Earle F. Philhower, III

# ADD TO ARDUINO SETTINGS-> ADDITIONAL BOARD MANAGER URLs
https://github.com/earlephilhower/arduino-pico/releases/download/global/package_rp2040_index.json

EXAMPLE CODE

    #include <LD2450.h>
    void setup()
    {
        //SERIAL FOR DEBUG MESSAGES
        Serial.begin(115200);
        // SETUP SENSOR USING HARDWARE SERIAL INTERFACE 1
        ld2450.begin(Serial1, false);  
    }

    void loop()
    {
        if (ld2450.read() > 0)
        {
            Serial.print(ld2450.getLastTargetMessage());
        }
    }

On the first upload attempt you may have to plug in the pico with pressed BOOT button. Please refer to earlephilhower/arduino-pico

The output on the serial monitor should be:

TARGET ID=1 X=-19mm, Y=496mm, SPEED=0cm/s, RESOLUTION=360mm, DISTANCE=496mm, VALID=1
TARGET ID=2 X=-1078mm, Y=1370mm, SPEED=0cm/s, RESOLUTION=360mm, DISTANCE=1743mm, VALID=1
TARGET ID=3 X=0mm, Y=0mm, SPEED=0cm/s, RESOLUTION=0mm, DISTANCE=0mm, VALID=0

For accessing the raw values, please access the RadarTarget struct using the getTarget function.

void loop(){
    const int found_targets = ld2450.read();
    if (found_targets > 0){
        for (int i = 0; i < found_targets; i++){
            const LD2450::RadarTarget valid_target = ld2450.getTarget(i);
            Serial.print("DISTANCE TO TARGET: ");
            Serial.println(valid_target.distance); // see struct RadarTarget
        }
    }
}

Further detailed examples can be found in the example folder.

DISCLAIMER AND NOTES

The library is based on the following projects:

RBEGamer/HLK-LD2450