Query RAID ctrlr version via RESTful API

[PaWeLL]

Hello.

I have many Proliant DL380 g9 servers.

I want to get information about RAID controller FW version form all of them via RESTful API.

I wrote script to do that:

$Address = 'IP'
$cred = Get-Credential
Disable-HPRESTCertificateAuthentication
$session = Connect-HPREST -Address $Address -Credential $cred
$systems = Get-HPRESTDataRaw -Href 'rest/v1/systems/1/smartstorage/arraycontrollers/0' -Session $session

echo $systems

It returns inforamtion abour RAID controller installed, but doesn't return FW version. 

FirmwareVersion                               : @{Current=}

How to return FW version by using this way?