Modbus Rtu Communication Protocol; Connection Setup; Read Holding Registers (Fc03) - ROBOTIQ 3-Finger Adaptive Robot Gripper Instruction Manual

4.7 MODBUS RTU communication protocol

The Robotiq 3-Finger Gripper can be controlled via RS485 or RS232 by using the Modbus RTU protocol. This section is intended to provide guidelines
for setting up a Modbus scanner that will adequately communicate with the Gripper.
For a general introduction to Modbus RTU and for details regarding the CRC algorithm, the reader is invited to read the Modbus over serial line
specification and implementation guide available at: http://www.modbus.org/docs/Modbus_over_serial_line_V1.pdf.
For debugging purposes, the reader is invited to download one of many free Modbus scanners, such as the CAS Modbus Scanner from Chipkin
Automation Systems, which is available at: http://www.chipkin.com/cas-modbus-scanner.
Caution
The Adaptive Gripper register values are updated at a 100Hz frequency. It is therefore recommended to send commands with a minimum
interval delay of 10ms. Note that the updated frequency may drop under some conditions where the response time would be longer.

4.7.1 Connection setup

The following table describes the connection requirements for controlling the Robotiq 3-Finger Gripper using the Modbus RTU protocol.
Robot Output / Gripper Input First Register
Robot Input / Gripper Output First Register
Each register (word - 16 bits) of the Modbus RTU protocol is composed of 2 registers (bytes – 8 bits) from the Robotiq 3-Finger Gripper. The first
Gripper output Modbus register (0x07D0) is composed from the first 2 Robotiq 3-Finger Adaptive Robot Gripper registers (byte 0 and byte 1).

4.7.2 Read holding registers (FC03)

Function code 03 (FC03) is used for reading the status of the Gripper (robot input). Examples of such data are Gripper Status, Object Status, Finger
Position, etc.
Ex: This message asks for register 0x07D0 (2000) and register 0x07D1 (2001) which contains Gripper Status, Object Detection, Fault Status and
Position Request Echo.
Request is:
where
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PROPRIETY
Physical Interface
Baud Rate
Data Bits
Stop Bit
Parity
Number Notation
Supported Functions
Exception Responses
Slave ID
09 03 07 D0 00 02 C5 CE
3-Finger Adaptive Robot Gripper Instruction Manual
VALUE
RS485-RS232
115,200 bps
8
1
None
Hexadecimal
Read Holding Registers (FC03)
Preset Single Register (FC06)
Preset Multiple Registers (FC16)
Not supported
0x0009 (9)
0x03E8 (1000)
0x07D0 (2000)
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