@mitu Hey there - so just a quick update, I've managed to get the stick working - but it took some effort!

Firstly, you have to the stick into PS3 mode before the emulation station interface will recognise it, even then - it won't appear on-screen as a controller (the UI remains blank as if no controller is plugged in)- but if you hold down a button on the stick - it is suddenly recognised as a Brook PS3 controller and then configuration / calibration can start.

Emulation station refuses to recognise the L2 or R2 buttons, but you can configure the rest.

However I have noticed that it is then possible to get these buttons recognised after if you manually configure inputs in RetroArch(?) interace (the one with the green pixellated text that you access from in-game) - then with lots of fiddling around you can finally get the Wireless Brook Board working as a retro pie controller (as a wired PS3 controller)

I will try jstest next

Sorry for not posting details on setup - it's a RP4, with offiical usb-c power supply, (but was testing on RP2 with usb power last night) but will get the rest of the details when I can