SEN0676 mmWave Liquid Level Sensor Reference: API & Pinout

This article details the UART and Modbus protocol for liquid level detection, including register configurations, API functions, and the principles of FMCW technology.

Communication Protocol Description

Output: UART (Modbus protocol)

Register	Read and Write	Parameter Meaning	Instruct	Remark
0x0001	R/-	Empty Height	01 03 00 01 00 01 D5 CA	Unitmm, filtered data
0x0003	R/-	Water Level	01 03 00 03 00 01 74 0A	Unitmm, filtered data
0x0005	R/W	Installation Height	01 03 00 05 00 01 94 0B / 01 06 00 05 [AA] [BB] [CC] [DD]	Unit: cm Distance from radar to water bottom,water level equal to installation height minus Go high. To read the water level, first set the installation height.
0x03F4	R/W	Device Address	01 03 03 F4 00 01 C5 BC / 01 06 03 F4 [AA] [BB] [CC] [DD]	Range: 0x01 - 0xFD Broadcast support 0xFF
0x03F6	R/W	Baud Rate Adjustment	01 03 03 F6 00 01 64 7C / 01 06 03 F6 [AA] [BB] [CC] [DD]	48 96 144 192 384 560 576 1152 1290 Read, write baud rate, actual baud rate/100
0x07D4	R/W	Range	01 03 07 D4 00 01 C5 46 / 01 06 07 D4 00 [AA] [BB] [CC]	Default: 0X0A, unit mMaximum range is related to product model

API Description

   // Constructor: Initialize RX, TX pins and device address of the sensor
    LiquidLevelDetection(uint8_t rx_pin, uint8_t tx_pin, uint8_t device_addr = 0x01);
    
    // Initialize sensor communication, set baudrate
    bool begin(long baudrate = 115200);
    
    // Get current range (unit: meter)
    float getRange();
    
    // Get empty height (distance from sensor to liquid surface, unit: meter)
    float getEmptyHeight();
    
    // Set installation height (unit: centimeter)
    bool setInstallationHeight(float height_cm);
    
    // Get installation height (return unit: meter)
    float getInstallationHeight();
    
    // Get water level height (unit: meter)
    float getWaterLevel();

Principle

Utilizing Frequency Modulated Continuous Wave (FMCW) technology.

The radar operating frequency band is 80GHz, and the maximum range of 40m is the range of measurement. Depending on the size of the object's RCS, the maximum detection distance will have deviations. The measurement zero point of the millimeter wave module has been calibrated from the antenna surface to the lens end at the factory, and the measurement distance value will be calculated from the top of the lens.