Command Reference

This page documents all known commands for the S120 laser distance meter.

Command Format

All commands follow this structure:

F1 TT SS PP CC
│  │  │  │  └─ Checksum: sum(bytes[1:]) % 256
│  │  │  └──── Parameter byte
│  │  └─────── Sub-type byte
│  └────────── Type byte
└───────────── Frame header (always 0xF1)

Core Commands

Measurement Control

Command	Hex Code	Description
CLICK_MEASURE_BUTTON	`F1 04 01 01 06`	Trigger single measurement
START_CONTINUE_MEASURE	`F1 01 01 02 04`	Start continuous measuring
STOP_CONTINUE_MEASURE	`F1 04 03 00 07`	Stop continuous measuring
RETURN	`F1 04 00 01 05`	Return/cancel operation

Device Information

Command	Hex Code	Description
GET_DEVICE_MAC	`F1 03 02 05`	Get device MAC address
GET_DEVICE_VERSION	`F1 03 03 06`	Get firmware version
GET_DEVICE_BASE_INFO	`F1 02 02 01 05`	Get device information

Angle Reporting

Command	Hex Code	Description
OPEN_ANGLE_REPORT	`F1 02 03 01 06`	Enable inclinometer data
CLOSE_ANGLE_REPORT	`F1 02 03 00 05`	Disable inclinometer data

History

Command	Hex Code	Description
SYNC_HISTORY_DATA	`F1 03 01 14 18`	Request 20 history records

Dynamic Commands

These commands require calculated parameters:

SWITCH_MEASURE_MODE

Changes the active measurement mode.

F1 05 02 MM CC
         │  └─ Checksum
         └──── Mode code (see table below)

SWITCH_MEASURE_UNIT

Changes the measurement unit.

F1 05 02 UU CC
         │  └─ Checksum
         └──── Unit code

SWITCH_MEASURE_DATUM

Changes the measurement reference point.

F1 05 02 DD CC
         │  └─ Checksum
         └──── Datum code (front/middle/rear)

Mode Codes

Code	Mode	Chinese	Description
`01`	Single	单次测量	Single distance measurement
`02`	Continuous	连续测量	Continuous measurement
`03`	Area	面积测量	Area (Length × Width)
`04`	Volume	体积测量	Volume (L × W × H)
`05`	Wall Area	墙面面积测量	Wall surface area
`06`	Camera Area	摄像面积测量	Camera-based area
`07`	Angle+Height	测角测高	Angle and height
`08`	Triangle Height	求直角三角形高	Right triangle height
`09`	Triangle Hypotenuse	求直角三角形斜边	Right triangle hypotenuse
`0A`	Triangle Base Sum	求三角形底边和	Triangle base sum
`0B`	Triangle Aux Height	三角形辅助线高度测量	Triangle auxiliary height
`0C`	Triangle Area	三角形面积测量	Triangle area
`0D`	Trapezoid Area	梯形面积测量	Trapezoid area
`0E`	Cross-Section	断面测量	Cross-section
`0F`	Slope	坡面测量	Slope measurement
`10`	Height Tracking	高度跟踪	Height tracking
`11`	Azimuth	方位角测量	Azimuth angle
`12`	Stakeout	放样测量	Stakeout
`13`	Level Bubble	水平泡测量	Level bubble

Unit Codes

Code	Unit	Format
`00`	Meters	0.000 m
`01`	Feet-Inches	0’00” 0/32
`02`	Inches	0.000 in
`03`	Feet (decimal)	0.000 ft
`04`	Yards	0.000 yd

Code Examples

import asyncio
from bleak import BleakClient

SERVICE_UUID = "0000ae30-0000-1000-8000-00805f9b34fb"
CHAR_TX = "0000ae01-0000-1000-8000-00805f9b34fb"
CHAR_RX = "0000ae02-0000-1000-8000-00805f9b34fb"

def build_command(type_byte, sub_byte, param_byte):
    """Build a command packet with checksum."""
    packet = bytes([0xF1, type_byte, sub_byte, param_byte])
    checksum = sum(packet[1:]) % 256
    return packet + bytes([checksum])

async def trigger_measurement(client):
    """Send CLICK_MEASURE_BUTTON command."""
    cmd = build_command(0x04, 0x01, 0x01)  # F1 04 01 01 06
    await client.write_gatt_char(CHAR_TX, cmd)

async def get_device_version(client):
    """Send GET_DEVICE_VERSION command."""
    cmd = bytes([0xF1, 0x03, 0x03, 0x06])
    await client.write_gatt_char(CHAR_TX, cmd)

const SERVICE_UUID = '0000ae30-0000-1000-8000-00805f9b34fb';
const CHAR_TX = '0000ae01-0000-1000-8000-00805f9b34fb';

function buildCommand(type, sub, param) {
  const packet = new Uint8Array([0xF1, type, sub, param]);
  const checksum = (type + sub + param) % 256;
  return new Uint8Array([...packet, checksum]);
}

async function triggerMeasurement(characteristic) {
  const cmd = buildCommand(0x04, 0x01, 0x01);
  await characteristic.writeValue(cmd);
}

# Using mcbluetooth MCP tools

# Trigger measurement
bt_ble_write --adapter hci0 \
  --address 5B:A6:86:38:FA:CA \
  --char-uuid 0000ae01-0000-1000-8000-00805f9b34fb \
  --value "f104010106" \
  --value-type hex

# Get device version
bt_ble_write --adapter hci0 \
  --address 5B:A6:86:38:FA:CA \
  --char-uuid 0000ae01-0000-1000-8000-00805f9b34fb \
  --value "f1030306" \
  --value-type hex

Response Handling

After sending a command, responses arrive via notifications on 0xAE02 or indications on 0xAE05.

Response Prefix	Type	Description
`F1 01 01`	ACK	Continuous measure started
`F1 02 01`	Data	Single measurement data
`F1 02 04`	Data	Continuous measurement data
`F1 03 00`	Info	MAC address response
`F1 03 01`	Info	History data response
`F1 03 02`	Info	Device version (JSON)
`F1 04 01`	Result	Measurement result
`F1 05 01`	Error	Device error

See Response Reference for detailed response parsing.

Response Reference - Parse response packets
BLE Service Reference - GATT characteristics
Connecting Guide - Connection setup