PLC

Topics

PLCs

In ECMC, PLCs are a very powerful tool to handle EtherCAT data in real-time.

Since ecmccfg v7, the PLCs can be instantiated in 3 different ways:

pure text files

The simplest and most generic way to load plc file is by the loadPLCFile.cmd command:

${SCRIPTEXEC} ${ecmccfg_DIR}loadPLCFile.cmd,    "FILE=<filename>, INC=<include_dirs>, SAMPLE_RATE_MS=<rate_ms>, PLC_MACROS='<custom_macros>'"

pure yaml

Backwards compatibility for classic, text based PLCs is assured for yaml based.

yaml is - like python - indentation sensitive!

Indent with 2 spaces.

All keys are mandatory.

  • id: PLC id, unique uint
  • enable: PLC enabled at start
  • rateMilliseconds: execution rate in ms. To execute every cycle, independent of cycle rate, use -1.
  • code: dictionary of code lines.

Line terminator is still a pipe |, this is subject to change!

For more complex PLCs, it is highly advisable to use text based PLC definitions with a yaml header.

plc:
  id: 1
  enable: no
  rateMilliseconds: 10
  code:
    - 'ec0.s2.binaryOutput07:=global.test|'
    - '${PLC_ID}.enable:=plc0.enable|'
    - 'ec0.s2.binaryOutput05:=not(ec0.s2.binaryOutput05)|'
    - 'plc1.error:=12345|'

yaml header

Instead of the code dictionary, the file key can be used to load the PLC from a text file. The syntax of the text PLCs is kept from earlier versions.

All keys are mandatory.

  • id: PLC id, unique uint
  • enable: PLC enabled at start
  • rateMilliseconds: execution rate in ms. To execute every cycle, independent of cycle rate, use -1.
  • file: PLC text file to load.

If the file key is set, all definitions in the code dictionary are overwritten.

yaml header

plc:
  id: 1
  enable: yes
  rateMilliseconds: 10
  file: plc1.plc

PLC file

# this is a comment
println('plc1 from file');
println('plc1 from file # hash with inline comment'); # inline test
static.i:=static.i+1; # counter
println('i = # + - * / ', static.i); # println

iocsh call

${SCRIPTEXEC} "${ECMC_CONFIG_ROOT}loadYamlPlc.cmd" "FILE=./plc1File.yaml, ECMC_TMPDIR=/tmp/"