Reading and writing of string variables

Sample based on Beckhoff Infosys - Sample 04

Task

A .Net application should read a string from the PLC and write a string to the PLC.

Description

The PLC contains the string MAIN.text.

PLC program

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PROGRAM MAIN
VAR
 text : STRING[30] := 'hello';
END_VAR

F# program

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#r "FSharp.Plc.Ads.dll"
//using IEC 61131-3 type aliases for convenience
#r "NuSoft.FSharp.IEC.DataTypes.dll"
open FSharp.Plc.Ads.Experimental
open System
let amsNetId = "192.168.68.132.1.1"
let amsPort = 801
//instantiate builder for specific TwinCAT instance
let plc = createClient amsNetId amsPort

let myInput = "hello PLC world!!!"

plc {
  writeAny "MAIN.text" myInput
}
|> function 
  | Choice1Of3 _ -> ()// handle success
  | Choice2Of3 errMsg -> ()// handle error
  | Choice3Of3 (adsCode,additionalInfo) -> ()// handle ADS error

plc {
  readAny "MAIN.text"
}
|> function 
  | Choice1Of3 (res: string) -> ()// handle success
  | Choice2Of3 errMsg -> ()// handle error
  | Choice3Of3 (adsCode,additionalInfo) -> ()// handle ADS error

namespace Microsoft.FSharp

Multiple items
type ExperimentalAttribute =
  inherit Attribute
  new : message:string -> ExperimentalAttribute
  member Message : string

Full name: Microsoft.FSharp.Core.ExperimentalAttribute

--------------------
new : message:string -> ExperimentalAttribute

namespace System

val amsNetId : string

Full name: Readwritestring.amsNetId

val amsPort : int

Full name: Readwritestring.amsPort

val plc : (obj -> Choice<string,obj,(obj * obj)>)

Full name: Readwritestring.plc

val myInput : string

Full name: Readwritestring.myInput

union case Choice.Choice1Of3: 'T1 -> Choice<'T1,'T2,'T3>

union case Choice.Choice2Of3: 'T2 -> Choice<'T1,'T2,'T3>

val errMsg : obj

union case Choice.Choice3Of3: 'T3 -> Choice<'T1,'T2,'T3>

val adsCode : obj

val additionalInfo : obj

val res : string

Multiple items
val string : value:'T -> string

Full name: Microsoft.FSharp.Core.Operators.string

--------------------
type string = String

Full name: Microsoft.FSharp.Core.string