SDO acyclic exchange using ROS2 services

Service Data Objects (SDO) contain object dictionary entries that can be exchanged acyclically. SDO works as a mailbox sending and buffering received data. This communication is acyclic and is dependent on available bandwidth in the communication cycle. This communication is not deterministic and is best suited for transmitting configuration data.

Services

The EtherCAT Driver ROS2 stack comes with a service server that allows the exchange of data with an EtherCAT slave using ROS2 services through SDO. The following services are available:

Service	Interface	Description
`ethercat_manager/get_sdo`	`ethercat_msgs::srv::GetSdo`	Read data from slave SDO register
`ethercat_manager/set_sdo`	`ethercat_msgs::srv::SetSdo`	Write data to slave SDO register

Interfaces

The interfaces used by the services are defined such that:

ethercat_msgs::srv::GetSdo

ethercat_msgs::srv::SetSdo

Request

int16 master_id
uint16 slave_position
uint16 sdo_index
uint8 sdo_subindex
string sdo_data_type

int16 master_id
int16 slave_position
uint16 sdo_index
uint8 sdo_subindex
string sdo_data_type
string sdo_value

Response

bool success
string sdo_return_message
string sdo_return_value_string
float64 sdo_return_value

bool success
string sdo_return_message

Usage

Build and source the ethercat_manager package and run:

$ ros2 run ethercat_manager ethercat_sdo_srv_server