EVA ICS v4 EAPI

rPLC can be connected to EVA ICS v4 via native BUS/RT and use API to accept actions and synchronize variables with EVA ICS items.

Note

The described functionality requires eva crate feature.

Action pool size

The default action pool size is 1, meaning there can be only a single action running. Despite context actions are atomic (they only set context variables to specified values), the pool can be increased with the top-level field in PLC YAML configuration:

eapi:
  action_pool_size: 4

Block configuration

EAPI I/O should be defined in PLC config YAML as:

io:
- id: someblock # id must be 14 chars as max
  kind: eapi
  input:
    # input block configurations (array)
  output:
    # output block configurations (array)

rPLC process can be connected only to one EVA ICS node so the only one I/O block should be used.

Input blocks

Input blocks (actions) should be defined as:

io:
- id: someblock # id must be 14 chars as max
  kind: eapi
  input:
    - action_map:
      - oid: unit:tests/u1
        value: u1_val
      - oid: unit:tests/u2
        value: u2_val
  output:
    # ....

The variables are set as soon as the PLC process receives an action from the connected EVA ICS node.

Note

Actions do not synchronize variables/items with EVA ICS automatically. To synchronize a variable it must be present in an output block.

Output blocks

Output blocks should be defined as:

io:
- id: someblock # id must be 14 chars as max
  kind: opcua
  config:
    # .....
  input:
    # .....
  output:
    - oid_map:
      - oid: sensor:tests/outvar1
        value: outvar1
      - oid: sensor:tests/outvar2
        value: outvar2
      sync: 500ms
    - oid_map:
      - oid: unit:tests/u1
        value: u1_val
      - oid: unit:tests/u2
        value: u2_val
      sync: 1s
      # shift I/O loop if required
      #shift: 100ms
      cache: 30s

The field sync is mandatory and specifies how frequently the block must be synchronized.

The field cache is optional. If an output variable is cached, its state is not synchronized with EVA ICS node until the cache expires.

Real-time

EAPI threads usually do not require to be set as real-time-ones.

Connecting to EVA ICS node

EVA ICS node connection settings are not compiled into rPLC process as this configuration may be changed in production from time to time.

To connect a process to EVA ICS node, launch it with PLC_EAPI environment variable set:

PLC_EAPI=192.168.1.11:7777 ./myplc

The variable also may contain additional parameters:

# the buf_ttl is in microseconds
PLC_EAPI=192.168.1.11:7777,timeout=5,buf_size=8192,queue_size=8192,buf_ttl=10 ./myplc

EVA ICS node must accept EAPI TCP connections. To allow it, edit eva/config/bus EVA ICS node configuration key, e.g. with eva-shell:

eva edit config/bus

Accessing PLC instance from EVA ICS

Basics

The processes are connected to EVA ICS node bus as:

fieldbus.HOSTNAME.plc.PROCESSNAME

The connected processes can be listed with e.g. eva-shell:

eva broker client.list -x fieldbus

Note

The connected PLC processes are not native EVA ICS services so they are not listed in the node service list.

Unit actions

To use rPLC as an action handler for EVA ICS units, set the unit action handler as:

eva item edit unit:tests/u1

action:
    svc: fieldbus.HOSTNAME.plc.PROCESSNAME

API calls

rPLC internal API methods can be accessed via EAPI as well:

eva svc call fieldbus.mws1.plc.all info