LRF1200A1 UART protocol and integration

LRF1200A1 905 nm Laser Rangefinder Module

Typical applications: Handheld optics, Industrial ranging, Security optics.

Price and buy on erdilrf.comRequest STEP file

At a glance

Protocol family	Family A (55 AA, polled)
Default baud	115200 bps, 8N1
Frame	8 bytes
Distance unit on the wire	metres x 10
Measurement range (datasheet)	see specification

Specification

Values come from the ERDI datasheet for this model. Where the datasheet gives a condition, it is shown.

Parameter	Value	Condition
Ranging accuracy	±1 m (5–100 m) · ±(1 + L×0.4%) m (>100 m)
Ranging frequency	1–3 Hz
Interface	UART, TTL 3.3 V
Supply voltage	3.3 V ± 0.1 V
Dimensions	Φ23 × 40 mm
Weight	18 g
Protection rating	On request
Laser safety class	Class 1	Per product title, "eye-safe"
Operating temperature	On request
Measuring range	≥5–1,200 m	Building target
Display resolution	0.1 m

Pinout and wiring

The pin table for this exact variant is in the model datasheet (see Resources). The connector and wire specification is in the specification table above.

Cross TX and RX (module TX to host RX), share ground, and power the module from a supply that matches the supply voltage in the specification table. See Wiring and power.

Protocol summary

• Frame: 8 bytes, header 55 AA, then function code, four data bytes, checksum.
• Default baud: 115200 bps, 8 data bits.
• Transmit checksum: lower 8 bits of function code + D1..D4 (the header is not included).
• Reply checksum: lower 8 bits of header H + header L + function code + D1..D4 (the header is included). The two formulas differ on purpose.
• Reply to a ranging command: 55 AA <fn> STA FF DIS_H DIS_L SUM. STA = 1 means the measurement succeeded.
• Distance: DIS_H:DIS_L is the measured value in metres multiplied by 10.

Command	Request frame
Single-shot ranging	55 AA 88 FF FF FF FF 84
Continuous ranging	55 AA 89 FF FF FF FF 85
Stop ranging	55 AA 8E FF FF FF FF 8A
Angle measurement	55 AA 8A FF FF FF FF 86

:::caution Continuous ranging For this model the manual's continuous-ranging request uses function byte 0x89 while the recorded reply uses 0x88. Poll with single-shot (0x88) until ERDI confirms the behaviour for your batch. :::

The full frame description is in Family A protocol. Try it without installing anything in the browser serial monitor.

Code examples

Python

pip install erdi-lrf   # PyPI, MIT
erdi-lrf --port /dev/ttyUSB0 --model LRF1200A1 measure

from erdi_lrf import ErdiLRF

with ErdiLRF("/dev/ttyUSB0", "LRF1200A1") as lrf:   # COM3 on Windows
    r = lrf.measure()                          # single-shot (0x88)
    print(f"{r.metres:.3f} m", "raw", r.raw)

Arduino

#include <ErdiLRF.h>

ErdiLRF lrf(Serial1, ERDI_LRF1200A1);

void setup() {
  Serial.begin(115200);
  Serial1.begin(erdiDefaultBaud(ERDI_LRF1200A1));   // 115200 baud; ESP32: Serial1.begin(baud, SERIAL_8N1, RX_PIN, TX_PIN)
  lrf.setTimeout(1000);
}

void loop() {
  ErdiMeasurement m;
  if (lrf.measure(&m) == ERDI_OK) {
    Serial.println(m.metres, 3);
  }
  delay(200);
}

ESPHome

external_components:
  - source: github://ErdiTech/erdi-lrf-home-assistant
    components: [erdi_lrf]

uart:
  id: lrf_uart
  tx_pin: GPIO17
  rx_pin: GPIO16
  baud_rate: 115200

sensor:
  - platform: erdi_lrf
    uart_id: lrf_uart
    model: LRF1200A1
    name: "Laser distance"
    update_interval: 1s

ROS 2

cd ~/ros2_ws/src && git clone https://github.com/ErdiTech/erdi_lrf_driver.git
cd ~/ros2_ws && rosdep install --from-paths src --ignore-src -y && colcon build --packages-select erdi_lrf_driver
source install/setup.bash
ros2 launch erdi_lrf_driver erdi_lrf.launch.py port:=/dev/ttyUSB0 model:=LRF1200A1 rate:=10.0
ros2 topic echo /range

Platform status

Only rows with evidence say Verified. See the compatibility matrix for what that means and where the evidence is.

Platform	Status	Guide
Python (erdi-lrf)	Untested	Python / Raspberry Pi / Jetson
Arduino / PlatformIO	Untested	Arduino / PlatformIO
ESPHome / Home Assistant	Untested	ESPHome
ROS 2	Untested	ROS 2
ArduPilot (Lua script)	Untested	ArduPilot
ArduPilot native driver	No driver yet	ArduPilot

Known issues

• The datasheet notes that the send and receive checksums are computed over different bytes (see Protocol). Use separate functions for the two directions.
• UART logic level is not stated as a separate field for most models. Supply voltage is not the UART voltage: check the module's TX level against your host before wiring, or ask us.

Resources

• Model page with datasheet download: https://erdilrf.com/models/lrf1200a1/
• Datasheet and specification page: LRF1200A1 datasheet and specs
• Interactive 3D view: LRF1200A1 3D viewer
• STEP model: available on request, Request STEP
• Drivers and protocol notes: ErdiTech/erdi-lrf-drivers
• Questions: tommy@erdimail.com, +86 133 0819 5790