Open Serial Port with variable - powershell

Question

I want to open a COM port in my powershell script:
function openComPort($number, $baud) {
$port = New-Object System.IO.Ports.SerialPort("COM$number", $baud, "None", 8, "One")
$port.Open()
return $port
}
$myOpenedPort = openComPort(1, 9600)
This fails with
New-Object : Exception calling ".ctor" with "5" argument(s): "Positive number required.
Parameter name: BaudRate"
At line:9 char:20
+ $port = New-Object <<<< System.IO.Ports.SerialPort("COM$number", $baud, "None", 8, "One")
+ CategoryInfo : InvalidOperation: (:) [New-Object], MethodInvocationException
+ FullyQualifiedErrorId : ConstructorInvokedThrowException,Microsoft.PowerShell.Commands.NewObjectCommand
You cannot call a method on a null-valued expression.
At line:11 char:12
+ $port.Open <<<< ()
+ CategoryInfo : InvalidOperation: (Open:String) [], RuntimeException
+ FullyQualifiedErrorId : InvokeMethodOnNull
What am I doing wrong?

Answer 1

You're calling your function wrong, Powershell (unlike other languages) doesn't require brackets when calling a function, see about_functions for further info.
Using them like that groups everything inside the brackets into a single item, this is being sent to the first parameter $number, leaving $baud empty - which is causing your errors.
The correct syntax is:
openComPort 1 9600
EDIT: It's also good practice to have your params into a param() block (this is a step towards using advanced functions.
And to also set a param type to ensure you receive the correct input type. They are both int in this case - as you only want a positive whole number.
This would update your function to:
function openComPort {
Param(
[int]$number,
[int]$baud
)
$port = New-Object System.IO.Ports.SerialPort("COM$number", $baud, 'None', 8, 'One')
$port.Open()
return $port
}
$myOpenedPort = openComPort -number 1 -baud 9600