Hi-Link - HLK-LD6004 - Pinout & Setup
For a recent project i wanted a MMWave 3.3v sensor that could detect multiple people, the LD6004 fit this use case. When my order arrived i struggled to find any documentation for the pinouts in English but i managed to find the below as part of the product launch blog (translated).
Most other Hi-Link products have a google drive link with the documentation, i cant find one for this yet. Those looking to integrate now, i suggest you refer to the documentation or the HLK-LD6002B. The communication protocol specification should help plus there are a number of existing libraries\tools on GitHub
Test Script
Quick little script to get you going. Grab it from GitHub Here ld6004_monitor.py
Just pass the Serial Port
python3 ld6004_monitor.py /dev/ttyUSB01
Wiring

If you are using their kit and breakout cable the below. the USB to serial Adapter is a CH340

Specifications
- Module: HLK-LD6004
- Chip: ADT6101P (57-64 GHz FMCW, 2T2R AIP antenna, ARM Cortex-M3, 1MB flash)
- Frequency: 60GHz mmWave FMCW
- Detection range: 0-6m (wall-mounted)
- Beam: horizontal/vertical +/-60 degrees
- Multi-target: Up to 3 persons, real-time x, y, z coordinates
- Auxiliary data: Distance and speed (Doppler index)
- Module size: 25 x 31.5 mm
- Power Supply: 3.1-3.5V, 135-600mA
- Interface: UART + GPIO
- Closest sibling: HLK-LD6002B (identical protocol, same chip family)