LZ-01 masterCtrlV2.0 Modbus RTU Communication Protocol

Version: V2.2 | Update Date: 2026-03-01

---

1. Communication Parameters

Item	Parameter
Physical Interface	RS-485 Half-Duplex
Baud Rate	115200 bps
Data Bits	8 bits
Parity	None
Stop Bits	1 bit
Protocol Type	Modbus RTU
Default Slave ID	1 (Right Hand) / 2 (Left Hand)
Response Timeout	20ms
Serial Buffer	256 Bytes

2. Supported Function Codes

Function Code	Name	Description
0x03	Read Holding Registers	Read holding registers, supports batch reading
0x06	Write Single Register	Write a single register
0x10	Write Multiple Registers	Write multiple registers, supports batch writing

3. Register Address Overview

Address Range	Area	R/W	Description
0~5	Motor Position Control	RW	Set target position, Read returns actual position (0~1000 ‰)
6~11	Motor Speed Control	RW	Set target speed, Read returns actual speed (0~1000 ‰)
12~17	Motor Torque Control	RW	Set torque limit, Read returns actual torque (‰)
18~30	Pressure Sensors	RO	Pressure measurements (Unit: mN)
31~40	Joint Angles	RO	Joint actual angles (Unit: 0.1°)
41~46	Motor Position Feedback	RO	Actual position feedback (0~1000 ‰)
47~56	Angle Calibration	RW	Encoder calibration parameters
57	System Control	RW	Flash save command
58~63	Error Logs	RO	Error flags / Count / Status
66	Latest Error Code	RO	Most recent error code
67	Error Clear	WO	Write 1 to clear all error counters and flags
70~75	Motor Speed Feedback	RO	Actual speed feedback (0~1000 ‰)
76~81	Motor Torque Feedback	RO	Actual torque feedback (‰)

---

4. Register Detailed Definitions

4.1 Motor Control Registers (Address 0~17, R/W)

Value range: 0~1000 (‰).

Read-Write Reflection Mechanism: For convenience in unified control and monitoring, reading these 18 registers returns real-time measured values instead of set-points:

• Read 0~5: Returns actual motor position
• Read 6~11: Returns actual motor speed
• Read 12~17: Returns actual motor torque

Position Command (Address 0~5)

Address	Name	Description
0	pos_cmd[0]	Thumb rotation motor target position
1	pos_cmd[1]	Thumb pinch motor target position
2~5	pos_cmd[2~5]	Index / Middle / Ring / Little target position

Speed Command (Address 6~11)

Default value: 1000 (Full Speed).

Torque Limit Command (Address 12~17)

Default value: 1000 (Max Torque).

4.2 Pressure Sensor Registers (Address 18~30, Read-Only)

Unit: mN (milli-Newton).

Address	Name	Targeted Part
18~19	pressure[0~1]	Thumb
20~21	pressure[2~3]	Index
22~23	pressure[4~5]	Middle
24~25	pressure[6~7]	Ring
26~27	pressure[8~9]	Little Finger
28~30	pressure[10~12]	Palm

4.3 Joint Angle Registers (Address 31~40, Read-Only)

Unit: 0.1°.

Address	Name	Finger
31~32	angle[0~1]	Thumb (J1/J2)
33~34	angle[2~3]	Index (J1/J2)
35~36	angle[4~5]	Middle (J1/J2)
37~38	angle[6~7]	Ring (J1/J2)
39~40	angle[8~9]	Little Finger (J1/J2)

---

5. Error Code Definitions

last_err_code (Address 66) format: 0xTTII (High Byte=Type, Low Byte=Device ID):

Type Code	Meaning
0x01	Communication Timeout
0x02	Device Connection Failed
0x03	Data Read Failed
0x04	Abnormal Initialization
0x05	Mechanical Homing Timeout

---

6. Communication Examples

6.1 Read All Actual Motor Positions (Address 41~46)

Request: 01 03 00 29 00 06 [CRC16]
Response: 01 03 0C [12-byte data] [CRC16]

6.2 Set Thumb Rotation Position to 50% (500‰)

Request: 01 06 00 00 01 F4 [CRC16]
Response: 01 06 00 00 01 F4 [CRC16]

---

7. Data Flow Diagram

---

8. Precautions

1. Initialization: Check hand_status (Address 62) after power-on. A value of 1 indicates that homing is complete and the system is ready for control.
2. Frequency: Recommended Modbus polling frequency is between 10ms - 50ms.
3. Parameter Saving: After modifying calibration parameters, write 1 to save_cmd (Address 57) to trigger permanent Flash storage.