Call the method listDevices to get all devices from a ccu2 (homematic basis station)

listDevices.ps1

$homematicUrl = 'http://192.168.10.21:2001'
$body = @'
<?xml version="1.0"?>
<methodCall>
  <methodName>listDevices</methodName>
</methodCall>
'@

$response = Invoke-WebRequest -Uri $homematicUrl -Method Post -Body $body

# Pretty Print
$doc= New-Object System.Xml.XmlDataDocument
$doc.LoadXml($response)
$sw= New-Object System.Io.Stringwriter
$writer = New-Object System.Xml.XmlTextWriter($sw)
$writer.Formatting = [System.Xml.Formatting]::Indented
$doc.WriteContentTo($writer)
$sw.ToString()