Thank you @mitu for all help. I almost finish my image from other posts you helped me to solve. In the case of the game pads I write a solution worked for me, just in case someone is lost and can be useful. This is the solution:
Finally I could make work two 8bitdo SN30 Pro 2 game pads. I used the firmware V1.2 and worked pretty with this same technique. However, I wanted to try with the latest V1.3 firmware to see what happens and I could make work. Fighting with the retro arena setup and also retropie setup both versions in the bluetooth script, it just worked for me the first time and after the first time is impossible, at least for me, to pair again by the horrible error Already exists bluez.org. Something is stored in the cache or somewhere after the first pairing but I could not find information in any place. Most of posts run from a real solution and they mention “my solution was begin with a fresh image and problem solved”. I made that but if you have a mistake, like in my case, is an endless loop over and over again and no solution. Then this is what I did:
First I made a copy, to have safe the original file “/etc/dbus-1/system.d/bluetooth.conf”. Then I replaced that file with this:
https://pastebin.com/LufCYWy9
Then I made this procedure to pair:
1.-sudo service bluetooth restart
2.-agent on
3-power on
4.-scan on
5.-scan off
6.-pair “mac address of the gamepad”
7.-connect “mac address of the gamepad”
At this is step it will pair although and is possible it can says cannot connect. No matter this is not a thing to be afraid. If it doesn’t connect or says fail to connect in specific: Turn OFF if it is ON the game pad. Turn ON again normally the game pad and type again step 7 (connect with the mac address command).
It can says a couple (2 or 3) times is not possible connect but no matter it will do. Simply is turn OFF the game pad and ON again and give the “connect” command again. Once say successfully connected is give this command:
8.-trust “mac address of the gamepad”
9.-Return the original file “/etc/dbus-1/system.d/bluetooth.conf”, deleting the one of pastebin above described. Just in case. I used the pastebin temporary just to pair, after pair there is no sense to keep it.
If in the step 6 of pairing says already exists bluez.org or simply never connected in step 7 then is type first to see the devices paired:
devices
After that is check if i there the game pad. If it’s there then is give now:
remove “mac address of the gamepad”
One is successfully removed is back to step 5.
Once is paired, and connected, because It will pair for sure, also will be detected ALL the buttons by emulation station. I have two gamepads and both were detected including after reboot and latest firmware. I tested this like 10 times to be sure, including making tests downgrading and upgrading firmware in the game pads and always worked at the end. I write this just in case someone has a problem as me and want time and loss time beginning from fresh image and is wanted to save time.