BLE Service Reference

This page documents the Bluetooth Low Energy GATT services and characteristics exposed by the Huepar S120.

Device Advertisement

Field	Value
Device Name	`LDM-S120 xxxx` (xxxx = last 4 hex of MAC)
Address Type	Random (BLE random address)
Advertised Services	None during scanning
Manufacturer Data	None

GATT Services

Generic Access (0x1800) Standard

Characteristic	UUID	Properties	Value
Device Name	0x2A00	read, write	`LDM-S120 faca`
Appearance	0x2A01	read	`0x0000` (Unknown)

Generic Attribute (0x1801) Standard

Characteristic	UUID	Properties	Purpose
Service Changed	0x2A05	indicate	GATT service change notifications

Custom Laser Meter Service (0xAE30)

This is the primary service for device communication.

Full UUID: 0000ae30-0000-1000-8000-00805f9b34fb

Characteristic	UUID	Handle	Properties	Purpose
Command TX	0xAE01	0x000A	write-without-response	Send commands to device
Data RX	0xAE02	-	notify	Receive measurement data
Status RX	0xAE05	-	indicate	Receive status/errors

Characteristic Details

0xAE01 - Command TX

Direction: App → Device

Used to send all commands to the device. Commands must follow the LDMv1 packet format.

┌────────┬──────────┬──────────┬──────────┐
│ Header │ Command  │ Payload  │ Checksum │
│  0xF1  │  1 byte  │ 0-N bytes│  1 byte  │
└────────┴──────────┴──────────┴──────────┘

Properties:

write-without-response - No ACK from BLE stack
Maximum write size: 20 bytes (BLE default MTU)

Example:

F1 00 00 F1  // Trigger measurement
│  │  │  └── Checksum: (0x00 + 0x00) % 256 = 0x00... wait, this is 0xF1
│  │  └───── Payload: none
│  └──────── Command: CLICK_MEASURE_BUTTON
└─────────── Header

0xAE02 - Data RX (Notify)

Direction: Device → App

Used for measurement data and device information responses. Enable notifications to receive data.

Response format varies by command:

Response Type	Prefix	Description
Measurement	`F1 01`	Distance/area/volume results
MAC Address	`F1 03 00`	Device MAC as ASCII
Version	`F1 03 02`	JSON firmware info
History	`F1 03 01`	Stored measurements

Enabling notifications:

# Python (bleak)
await client.start_notify(
    "0000ae02-0000-1000-8000-00805f9b34fb",
    notification_handler
)

0xAE05 - Status RX (Indicate)

Direction: Device → App

Used for status updates and error reporting. Uses indicate (with ACK) for reliability.

Common responses:

Status	Meaning
`Err 1`	Target too far
`Err 2`	Target too close
`Err 3`	Excessive ambient light
`Err 4`	Out of range

Service UUIDs by Manufacturer

Different manufacturers use different service UUIDs:

Manufacturer	Service UUID	Notes
Longshuo (Huepar S120)	0xAE30	This device
SNDway	0xFFF0	Different protocol variant
Xintong	0x1000	Unknown protocol
Levelsure	0xFFF0	Laser levels
Levelsure 603BT	0xFFA0	Different model
Levelsure DP	0xFFE0	DP series

Connection Requirements

Linux (BlueZ)

# Must trust before connecting
bluetoothctl trust 5B:A6:86:38:FA:CA
bluetoothctl connect 5B:A6:86:38:FA:CA

Android/iOS

Direct connection works without explicit trust step - the OS handles this automatically.

MTU Considerations

Platform	Default MTU	Notes
Android	23 bytes	Can negotiate higher
iOS	185 bytes	Automatic negotiation
Linux	23 bytes	Use `bt_gatt_exchange_mtu`

The S120 commands are all under 20 bytes, so default MTU is sufficient.

Command Reference - All available commands
Response Reference - Response packet formats
Connecting Guide - How to connect to the device