Help Needed with 24GHz mmWave Sensor on Raspberry Pi 5

Hello everyone,

I’m currently trying to integrate a 24GHz mmWave Radar sensor (Human Micro-Motion Detection, based on S3KM1110 and FMCW technology) with my Raspberry Pi 5, but I’m running into some issues. I’ve followed the connection and setup instructions as per the sensor’s official documentation, but I’m not getting any data output from the sensor. Here’s a quick rundown of my setup:

Wiring Configuration:

  • 3V3 to 3.3V
  • GND to GND
  • TX to RXD (GPIO 14 - pin 8)
  • RX to TXD (GPIO 15 - pin 10)

I have the UART pins configured as follows:

$ pinctrl get 14
14: a4    pn | hi // GPIO14 = TXD0

$ pinctrl get 15
15: a4    pu | hi // GPIO15 = RXD0

Raspberry Pi Configuration:
I followed the steps to disable serial port debugging and enable UART:

$ sudo raspi-config
# Selected Interfacing Options -> Serial -> no -> yes

$ cat /boot/firmware/config.txt  | grep uart

Sample Code Execution:
After setting up the environment and installing dependencies, I ran the provided demo, which only printed empty lines:

mkdir HMMD_mmWave_Sensor && cd HMMD_mmWave_Sensor
python -m venv env
source env/bin/activate
pip install pyserial
cd raspberry && python

To debug, I created a simple script to send hex commands and read the output, but it seems like there’s no data coming through:

import serial
import binascii
import time

def send_hex_string(serial_port, hex_string):
    hex_bytes = binascii.unhexlify(hex_string)
    print(f"Sending hex: {hex_string}")  # Debug: show what is being sent
    print("Data sent successfully.")  # Confirm data was sent

def read_serial_data(serial_port):
    print("Ready to receive data...")
    while True:
        if serial_port.in_waiting > 0:
            data = serial_port.readline().decode('utf-8', errors='ignore').strip()
            if data:
                print(f"Received: {data}")  # Debug: print received data
                print("Received data, but it's empty.")
            print("No data waiting.")
        time.sleep(1)  # Pause briefly, adjust as necessary for your context

if __name__ == "__main__":
        ser = serial.Serial('/dev/ttyAMA0', 115200, timeout=1)
        print("Serial port opened successfully.")
    except Exception as e:
        print(f"Failed to open serial port: {e}")

    hex_to_send = "FDFCFBFA0800120000006400000004030201"
    send_hex_string(ser, hex_to_send)

    except KeyboardInterrupt:
        print("Stopped by User")
        print("Serial port closed.")


Serial port opened successfully.
Sending hex: FDFCFBFA0800120000006400000004030201
Data sent successfully.
Ready to receive data...
No data waiting.
No data waiting.
No data waiting.
No data waiting.

Does anyone have any suggestions or insights into what might be going wrong? Any help or advice would be greatly appreciated.

Thanks in advance!

Is the Pi UART pins correct ? You could try swapping them.



Hey Reza,

I second what Michael has said. Swapping your TX and RX connections is a good starting point. Would you be able to let us know where you have found the documentation to see if it can give us any insight into this issue?

Thanks, Sam.

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Thank you, @Michael99645 and @Samuel.

Indeed, swapping the UART pins worked!

Would you be able to let us know where you have found the documentation to see if it can give us any insight into this issue?

I was using the official Waveshare documentation:

Thank you!

Great, I like things that are simple fixes.

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Awesome, glad this didn’t give you to much trouble.