HLK-LD1125H-Driver

This project provides a software interface for the HLK-LD1125H presence sensor, a hardware component meant to detect human presence in a certain area. You can read about the various aspects of the project below, if you don't care to do that feel free to download the latest release binaries from the GitHub release page in the repo. You wil find an amd64, and arm64 build. If you need to the project build to different specifications, simply build it from the source.

Quick Start

1. Download the release binaries from the GitHub release page.
2. Run the program using the correct binary for your distribution:

./hlk_ld1125h-amd64-0.0.5 /dev/ttyS0 /path/to/presence_data.fifo  # replace /dev/ttyS0 and /path/to/presence_data.fifo with the actual serial port of the sensor and desired path to the FIFO

3. Open another terminal and access the data from the pipe:

cat /path/to/your.fifo  # replace /path/to/your.fifo with the actual path to the FIFO

Project Structure

The project is structured as follows:

• root directory: The top-level directory of the project.
  • impl: Contains various implementations of the project. Currently, there are implementations in C and Kotlin.
  • docs: Contains any data sheets or other relevant information about the part.
  • version: Contains useful scripts and other utilities for auto incrementing the version.

C Implementation

The C implementation designs a Linux service that runs in the background, accessible by other implementations for extracting sensor data.

Overview

The C program is responsible for interfacing with the presence sensor over a serial port. The main functionality of the C program can be summarized as follows:

• It opens and configures a serial port.
• The program continuously reads data from the sensor, parsing this data into a specific format.
• The parsed data, in JSON format, is then written to a named pipe (FIFO) to make it accessible for other programs.
• The service can be stopped by sending a SIGTERM signal.
• The program ensures proper handling of leftover and invalid data samples.

Building and Running the C Program

The C program can be built using the provided Makefile in the repository. Here are the steps to do this from the terminal:

# navigate to the root directory of the project
cd HLK-LD1125H-Driver

# compile the program using the makefile
make

# the compiled output, named 'hlk_ld1125h', will be inside the 'build' directory
# to run the service, navigate to the 'build' directory and execute the following command:
./hlk_ld1125h-amd64-0.0.5 /dev/ttyS0 /path/to/presence_data.fifo  # replace /dev/ttyS0 and /path/to/presence_data.fifo with the actual serial port of the sensor and desired path to the FIFO

Please ensure that the correct serial port name and path to the FIFO are provided as command-line arguments when starting the service.

Stopping the Service

The service can be stopped gracefully by sending a SIGTERM signal to the process. You can do this from the command line using the kill command:

kill -TERM <pid>

Here is the process ID of the running service. You can get this ID by using the ps command or by storing it when starting the service.

Accessing the Sensor Data

Once the C service is up and running, it writes the sensor data to a named pipe (FIFO) as specified in the command line argument while starting the service. This data can be accessed by other services or a command line user by reading from this named pipe. To read the data from the command line, you can use the following command:

cat /path/to/your.fifo  # replace /path/to/your.fifo with the actual path to the FIFO

The data is written to the FIFO in JSON format, with the following structure:

{
  "timestamp": <UNIX timestamp>,
  "field1": "<occ or mov>",
  "field2": "<dis>",
  "distance": "<distance value>"
}

Here, the timestamp field represents the time when the data was written to the pipe. field1 can be either occ or mov depending on the status of the sensor. field2 is always dis, representing distance. The distance field contains the distance value read