101modbus protocol

This protocol is applicable to HWT101CT-485 and HWT101DT-485

101modbus protocol

Register Table

ADDR (Hex)	ADDR (Dec)	REGISTER NAME	FUNCTION	SERIAL I/F	Bit15	Bit14	Bit13	Bit12	Bit11	Bit10	Bit9	Bit8	Bit7	Bit6	Bit5	Bit4	Bit3	Bit2	Bit1	Bit0
00	00	SAVE	Save/Restart/Restore to Factory Defaults	R/W	SAVE[15:0]
04	04	BAUD	Serial port baud rate	R/W													BAUD[3:0]
1A	26	IICADDR	Device Address	R/W									IICADDR[7:0]
38	56	GY	Angular velocity Y	R	GY[15:0]
39	57	GZ	Angular velocity Z	R	GZ[15:0]
3F	63	Yaw	Heading Angle	R	Yaw[15:0]
41	65	AUTOPTP	Automatically obtain zero bias peak-to-peak value	R/W	AUTOPTP[15:0]
43	67	AUTOT	Automatically obtain zero bias time	R/W	AUTOT[15:0]
44	68	AUTOTH	Automatically obtain zero bias threshold	R/W	AUTOTH[15:0]
48	72	WORKMODE	Working Mode	R/W														WORKMODE[2:0]
4A	74	GYROPTP	Z-axis static peak-to-peak value	R/W	GYROPTP[15:0]
4B	75	GPTPTIME	Z-axis peak-to-peak acquisition time	R/W	GPTPTIME[15:0]
4C	76	GYROBAIS	Z-axis zero offset	R/W	GYROBAIS[15:0]
4D	77	GBAISSTIME	Z-axis zero offset acquisition time	R/W	GYROBAIS[15:0]
4E	78	GSTATICTHRE	Z-axis stationary threshold	R/W	GSTATICTHRE[15:0]
4F	79	GSTATICTIME	Z-axis stabilization time	R/W	GSTATICTIME[15:0]
50	80	PGSCALE	Z-axis calibration factor P	R/W	PGSCALE[15:0]
52	82	GSCALERANGE	Z-axis calibration angle	R/W	GSCALERANGE[15:0]
61	97	GYROCALITHR	Static detection threshold	R/W	GYROCALITHR[15:0]
63	99	GYROCALTIME	Gyroscope automatic calibration time	R/W	GYROCALTIME[15:0]
6A	106	WERROR	Gyroscope change value	R/W	GYROPTP[15:0]
6E	110	WZTIME	Angular velocity continuous stationary time	R/W	WZTIME[15:0]
6F	111	WZSTATIC	Angular velocity integral threshold	R/W	WZSTATIC[15:0]
74	116	MODDELAY	485 data response delay	R/W	MODDELAY[15:0]
76	118	CALIYAW	Z axis angle reset	R/W	CALIYAW[15:0]

Read register format

• The data is sent in hexadecimal format, not ASCII.

• Each register address, register number, and data are represented by two bytes. The high and low bits of the register address are represented by ADDRH and ADDRL, the high and low bits of the register number are represented by LENH and LENL, and the high and low bits of the data are represented by DATA1H and DATA1L.

• The last two digits of the read instruction are standard CRC check bits. You can use the CRC check bit calculation tool to calculate it. CRC online calculation website .

Send command

Modbus Address	Function code	Register high 8 bits	Register lower 8 bits	Read length high 8 bits	Read length lower 8 bits	Check digit high 8 bits	Check digit lower 8 bits
ID	0x03 (Read)	ADDRH[15:8]	ADDRL[7:0]	LENH[15:8]	LENL[7:0]	CRCH[15:8]	CRCL[7:0]

Data return

Modbus Address	Function code	Read length	Data high 8 bits	Data lower 8 bits	Data high 8 bits	Data lower 8 bits	Data high 8 bits	Data lower 8 bits	Check digit high 8 bits	Check digit lower 8 bits
ID	0x03 (Read)	LEN[7:0]	DATA1H[15:8]	DATA1L[7:0]	…	…	DATAnH	DATAnL	CRCH[15:8]	CRCL[7:0]

Note: All the following examples are instructions when the Modbus address is 0x50 (default). If you change the Modbus address, you need to change the address and CRC check bit in the instruction accordingly.

GX~GZ (angular velocity)

Register name: GX~GZ Register address: 56~57 (0x38~0x39) Read/write direction: R Default value: 0x0000 Note: The y-axis angular velocity does not need to be read
Bit	NAME	FUNCTION
15:0	GY[15:0]	Angular velocity Y = GY[15:0]/32768*2000°/s
15:0	GZ[15:0]	Angular velocity Z = GZ[15:0]/32768*2000°/s
Example: Send: 50 03 00 39 00 01 59 86 (read Z-axis angular velocity) Return: 50 03 02 GZH GZL CRCH CRCL GZ[15:0]=((short)GZH <<8)|GZL;

Roll~Yaw (angle)

Register Name: Roll~Yaw Register address: 63 (0x3F) Read/write direction: R Default value: 0x0000
Bit	NAME	FUNCTION
15:0	Yaw[15:0]	Heading angle Z = Yaw[15:0]/32768*180°
Example: Send: 50 03 00 3F 00 01 B9 87 (read Z-axis angle) Return: 50 03 02 YawH YawL CRCH CRCL Yaw[15:0]=((short)YawH <<8)|YawL;

Write register format

• The data is sent in hexadecimal format, not ASCII.

• Each register address and write data are represented by two bytes. The high and low bits of the register address are represented by ADDRH and ADDRL, and the high and low bits of the write data are represented by DATAH and DATAL.

Send command

Modbus Address	Function code	Register high 8 bits	Register lower 8 bits	Data high 8 bits	Data lower 8 bits	Check digit high 8 bits	Check digit lower 8 bits
ID	0x06 (Write)	ADDRH[15:8]	ADDRL[7:0]	DATAH[15:8]	DATAL[7:0]	CRCH[15:8]	CRCL[7:0]

Data return

Modbus Address	Function code	Register high 8 bits	Register lower 8 bits	Data high 8 bits	Data lower 8 bits	Check digit high 8 bits	Check digit lower 8 bits
ID	0x06 (Write)	ADDRH[15:8]	ADDRL[7:0]	DATAH[15:8]	DATAL[7:0]	CRCH[15:8]	CRCL[7:0]

Note: All the following examples are instructions when the Modbus address is 0x50 (default). If you change the Modbus address, you need to change the address and CRC check bit in the instruction accordingly.

CALIYAW (Z-axis angle reset to zero)

Register Name: CALIYAW Register address: 118 (0x76) Read/write direction: R/W
Bit	NAME	FUNCTION
15:0	CALIYAW[15:0]	Set the Z axis to zero: 0(0x00): Z axis reset
Example: Send: 50 06 00 76 00 00 65 91 ( Z-axis angle returns to zero ) Return: 50 06 00 76 00 00 65 91

SAVE (Save/Restart/Restore to Factory)

Register Name: SAVE Register address: 0 (0x00) Read/write direction: R/W Default value: 0x0000
Bit	NAME	FUNCTION
15:0	SAVE[15:0]	Save: 0x0000 Restart: 0x00FF Factory Reset: 0x0001
Example: Send: 50 06 00 00 00 FF C4 0B (restart) Return: 50 06 00 00 00 FF C4 0B

BAUD (serial port baud rate)

Register name: BAUD Register address: 4 (0x04) Read/write direction: R/W Default value: 0x0002
Bit	NAME	FUNCTION
15:4
3:0	BAUD[3:0]	Set the serial port baud rate: 0001(0x01): 4800bps 0010(0x02): 9600bps 0011(0x03): 19200bps 0100(0x04): 38400bps 0101(0x05): 57600bps 0110(0x06): 115200bps 0111(0x07): 230400bps
Example: Send: 50 06 00 04 00 06 45 88 (set serial port baud rate to 115200) Return: 50 06 00 04 00 06 45 88

IICADDR (device address)

Register Name: IICADDR Register address: 26 (0x1A) Read/write direction: R/W Default value: 0x0050
Bit	NAME	FUNCTION
15:8
7:0	IICADDR [7:0]	Set the device address for I2C and Modbus communication 0x01~0x7F
Example: Send: 50 06 00 1A 00 02 24 4D (set the device address to 0x02) Return: 50 06 00 1A 00 02 24 4D

WORKMODE (Z-axis operation mode)

Register Name: WORKMODE Register address: 72 (0x48) Read/write direction: R/W Default value: 0x0000
Bit	NAME	FUNCTION
15:4
3:0	WORKMODE[3:0]	Set the Z-axis operation mode: 0000(0x00): Normal data mode 0001(0x01): Peak-to-peak mode 0010(0x02): Request zero bias mode 0011(0x03): Calculate the scaling factor mode
Example: Send: 50 06 00 48 00 01 C5 9D (automatically obtain zero offset) Return: 50 06 00 48 00 01 C5 9D

GYROPTP (Z-axis static peak-to-peak value)

Register Name: GYROPTP Register address: 74 (0x4A) Read/write direction: R/W Default value: 0x0000
Bit	NAME	FUNCTION
15:0	GYROPTP[15:0]	Parameters used in calculating zero bias, automatically obtained by the sensor without setting
Write 0x01 to the "WORKMODE" register to enter the "Peak-to-Peak Mode". In this mode, the sensor automatically calculates the maximum and minimum Z-axis angular velocity within the time set by "GPTPTIME" and records them in "GYROPTP". This data will be used for zero bias calculation filtering in the "Zero Bias Mode". Z-axis static peak-to-peak value = GYROPTP/1000 (°/s) Example: Send: 50 03 00 4A 00 01 A8 5D (read the peak-to-peak value of the Z axis at rest) Return: 50 03 02 00 4B 05 BF 0x004B=75, Z-axis static peak-to-peak value = 75/1000=0.075 (°/s)

GPTPTIME (Z-axis peak-to-peak acquisition time)

Register Name: GPTPTIME Register address: 75 (0x4B) Read/write direction: R/W Default value: 0x000A
Bit	NAME	FUNCTION
15:0	GPTPTIME[15:0]	Calculate the peak-to-peak time, the default is 10S
Example: Send: 50 06 00 4B 00 0A 74 5A (Set the Z-axis peak-to-peak value acquisition time to 10S) Return: 50 06 00 4B 00 0A 74 5A After entering the "Peak-to-Peak Mode", the difference between the maximum and minimum Z-axis angular velocity within the " GPTPTIME " time is obtained and stored in "GYROPTP". This data will be used for zero bias calculation and filtering in the "Bias Mode " .

GYROBAIS (Z-axis zero bias value)

Register name: GYROBAIS Register address: 76 (0x4C) Read/write direction: R/W Default value: 0x0000
Bit	NAME	FUNCTION
15:0	GYROBAIS[15:0]	Horizontal gyro zero bias value, which can be obtained through "zero bias mode"
The Z-axis horizontal gyroscope has a certain zero bias value when it is stationary, and this zero bias value can be used to eliminate the angular velocity when it is stationary. The zero bias value can be automatically calculated by automatically obtaining the zero bias. Enter the "zero bias calculation mode" to automatically calculate the zero bias value based on the peak-to-peak value of "GYROPTP" and the zero bias acquisition time of "GBAISTIME". Z-axis zero bias value = GYROBAIS/1000 (°/s) Example: Send: 50 03 00 4C 00 01 48 5C (read the peak-to-peak value of the Z axis at rest) Return: 50 03 02 FF A9 C4 06 0x FFA9 = -87, Z-axis static peak-to-peak value = -87/1000 = -0.087 (°/s)

GBAISTIME (Z-axis zero bias acquisition time)

Register name: GBAISTIME Register address: 77 (0x4D) Read/write direction: R/W Default value: 0x000A
Bit	NAME	FUNCTION
15:0	GB A S TIME [15:0]	Time required for horizontal gyro zero bias calculation
Example: Send: 50 06 00 4D 00 0A 94 5B (Set the Z-axis zero offset acquisition time to 10S) Return: 50 06 00 4D 00 0A 94 5B The time required to obtain the Z-axis zero offset is used to obtain the zero offset value based on this time.

GSTATICTHRE (Z-axis static threshold)

Register Name: GSTATICTHRE Register address: 78 (0x4E) Read/write direction: R/W Default value: 0x0032
Bit	NAME	FUNCTION
15:0	GSTATICTHRE [15:0]	the GSTATICTHRE [15:0], the stronger the anti-vibration performance and the larger the error. GSTATICTHRE [15:0] is, the weaker the anti-vibration performance is and the smaller the error is. Default value: 50
The Z-axis horizontal gyroscope has slight data jitter when it is stationary. This parameter can filter out these slight jitters. When the angular velocity is less than the " GSTATICTHRE " setting value and lasts for the " GSTATICTIME" setting time, it is considered stationary and the Z-axis angular velocity is zero. When the scene with jitter causes Z-axis accumulation, this parameter can be appropriately increased. When it is used in a scene with very slow and uniform rotation, this parameter can be appropriately reduced. Z-axis zero offset value = GSTATICTHRE/1000 (°/s) Example: Send: 50 06 00 4E 00 64 E5 B7 (set the Z-axis static threshold to 0.1g) Return: 50 06 00 4E 00 64 E5 B7 0x0064=100，100/10000=0.1 (°)

GSTATICTIME (Z-axis stabilization time)

Register name: GSTATICTIME Register address: 79 (0x4F) Read/write direction: R/W Default value: 0x0064
Bit	NAME	FUNCTION
15:0	GSTATICTIME [15:0]	Z-axis determination of stationary time
Z-axis static judgment time threshold. When the angular velocity is less than the value set by "GSTATICTHRE" and lasts for the time set by "GSTATICTIME", it is considered static. If you have high requirements for stabilization time, you can appropriately reduce this parameter. Reducing this parameter can speed up the stabilization time but may also increase the error. Z-axis stabilization time = GSTATICTIME/1000 (s) Example: Send: 50 06 00 4F 00 64 B4 77 (set Z-axis stabilization time to 0.1s) Return: 50 06 00 4F 00 64 B4 77 0x0064=100, 100/1000=100ms

PGSCALE (Z-axis calibration factor P)

Register name: PGSCALE Register address: 80 (0x50) Read/write direction: R/W default value:
Bit	NAME	FUNCTION
15:0	PGSCALE [15:0]	Range: 0~20000 This parameter is written by the factory using a high-precision turntable. Please do not modify it.
There is an error in the Z-axis gyroscope measurement. This error is measured using a high-precision turntable at the factory and this parameter is written into the sensor. Do not modify this parameter unless necessary. This parameter can be automatically calculated in the "Calculation Factor Mode". After entering the "Calculation Factor Mode", the sensor can be rotated by the angle set by " GSCALERANGE " to calculate the calibration factor. Z-axis calibration factor P = PGSCALE/10000.0 Example: Send: 50 03 00 50 00 01 89 9A (read Z-axis calibration factor P ) Return: 50 03 02 27 3B 1F AB 0x273B = 10043, read the Z-axis calibration factor P = 10043 /10000=1.00430

GSCALERANGE (Z-axis angle calibration range)

Register Name: GSCALERANGE Register address: 82 (0x52) Read/write direction: R/W Default value: 0x02D0
Bit	NAME	FUNCTION
15:0	GSCALERANGE [15:0]	When calibrating factors, it is necessary to calibrate according to this parameter
Example: Send: 50 06 00 52 01 68 25 E4 (set Z-axis calibration angle to 360) Return: 50 06 00 52 01 68 25 E4 0x0168=360 The angle of rotation required in the Z-axis "scaling factor mode" is generally set to an integer multiple of 360°.

GYROCALITHR (gyro stationary threshold)

Register name: GYROCALITHR Register address: 97 (0x61) Read/write direction: R/W Default value: 0x0000
Bit	NAME	FUNCTION
15:0	GYROCALITHR[15:0]	Set the gyroscope inactivity threshold: Gyroscope static threshold = GYROCALITHR[15:0]/1000(°/s)
Example: Send: 50 06 00 61 00 32 54 40 ( set the gyroscope static threshold to 0.05 °/s) Return: 50 06 00 61 00 32 54 40 When the angular velocity changes less than 0.05 °/s and lasts for "GYROCALTIME", the sensor recognizes it as stationary and automatically resets the angular velocity less than 0.05 °/s to zero. The setting rule of the gyroscope static threshold can be determined by reading the value of the "WERROR" register. The general setting rule is: GYROCALITHR=WERROR*1.2, unit: °/s This register needs to be used in conjunction with the GYROCALTIME register.

GYROCALTIME (gyro automatic calibration time)

Register name: GYROCALTIME Register address: 99 (0x63) Read/write direction: R/W Default value: 0x03E8
Bit	NAME	FUNCTION
15:0	GYROCALTIME[15:0]	Set the gyroscope automatic calibration time
Example: Set the gyroscope automatic calibration time to 500ms Send: 50 06 00 63 01 F4 74 42 ( set high level alarm ) Return: 50 06 00 63 01 F4 74 42 When the angular velocity change is less than " GYROCALITHR " and lasts for 500ms, the sensor recognizes it as stationary and automatically resets the angular velocity less than 0.05 °/s to zero. This register needs to be used in conjunction with the GYROCALITHR register.

WERROR (gyroscope change value)

Register Name: WERROR Register address: 106 (0x6A) Read/write direction: R Default value: 0x0000
Bit	NAME	FUNCTION
15:0	WERROR[15:0]	Gyroscope change value = WERROR[15:0]/1000*180/3.1415926(°/s) When the sensor is stationary, the "GYROCALITHR" register can be set by changing this register

WZTIME (angular velocity continuous stationary time)

Register name: WZTIME Register address: 110 (0x6E) Read/write direction: R/W Default value: 0x01F4
Bit	NAME	FUNCTION
15:0	WZTIME[15:0]	Angular velocity continuous stationary time
Example: Send: 50 06 00 6E 01 F4 E5 81 ( set angular velocity continuous static time 500ms ) Return: 50 06 00 6E 01 F4 E5 81 When the angular velocity is less than " WZSTATIC" and lasts for 500ms, the angular velocity output is 0 and the Z-axis heading angle is not integrated. This register needs to be used in conjunction with the "WZSTATIC" register.

WZSTATIC (angular velocity integral threshold)

Register name: WZSTATIC Register address: 111 (0x6F) Read/write direction: R/W Default value: 0x012C
Bit	NAME	FUNCTION
15:0	WZSTATIC[15:0]	Angular velocity integral threshold = WZSTATIC[15:0]/1000(°/s)
Example: Send: 50 06 00 6F 01 F4 E5 81 ( set the angular velocity integral threshold to 0.5 °/s) Return: 50 06 00 6F 01 F4 E5 81 When the angular velocity is greater than 0.5 °/s, the Z-axis heading angle begins to integrate the acceleration When the angular velocity is less than 0.5 °/s and lasts for the time set by the register "WZTIME", the angular velocity output is 0 and the Z-axis heading angle is not integrated. This register needs to be used in conjunction with the "WZTIME" register.

MODDELAY (485 data response delay)

Register Name: MODDELAY Register address: 116 (0x74) Read/write direction: R/W Default value: 0x0BB8
Bit	NAME	FUNCTION
15:0	MODDELAY[15:0]	Set 485 data response delay, default is 3000, unit: us
Example: Send: 50 06 00 74 03 E8 C4 EF ( set 485 data response delay to 1000us) Return: 50 06 00 74 03 E8 C4 EF When the sensor receives the Modbus read command, the sensor delays 1000us and returns the data This register only supports the Modbus version of the sensor