Disable Onboard Bluetooth for RPi4

mickelsn

I am trying to fully disable the onboard Bluetooth for my Raspberry Pi 4 running Batocera 31. I want to have no power going to the built-in Bluetooth radio – I’m using the Retroflag NESPi 4 case which unfortunately has problems with WiFi and Bluetooth interference and it’s causing controller input lag for my 8bitdo SN30 Pro+ controllers. I have an off board USB Bluetooth dongle I plan to use instead.

I found these instructions for disabling Bluetooth on the board, but only the modification to the /boot/config.txt file is possible – the Batocera distribution doesn’t seem to have the systemctl command. Is that really all I need to do?

I’m new to Batocera for a total of 24 hours or so, moving over from being a RetroPie newbie…I really like this distro, and hope you guys can help me with this! My kids will greatly appreciate it… 😁

Atari

The sudo systemctl disable bluetooth.service is for disabling the high-level Bluetooth device management. You know, stuff like showing the devices in the Raspbian OS menu panel. Batocera does not use that to display Bluetooth devices and instead lets EmulationStation (the frontend menu) handle it. Disabling/enabling this would have no effect on your device’s input lag, so no need to worry about it.

You should be able to make the appropriate changes by editing batocera-boot.conf for your device as explained here. There should be a line related to ‘turn on/kill bluetooth’ (I can’t confirm as I don’t have my pi here with me). If it’s still not there, then you can edit the pi-specific boot config in /boot/boot/config.txt (yes that’s a boot folder within a boot folder). That file should contain all the familiar Pi stuff like #hdmi_safe=1 and dtparam=foobar.

You could also use basic user scripting if you just want to run the commands at boot every time. https://wiki.batocera.org/launch_a_script

mickelsn

Thanks, I’ll check that out later today. Just to confirm – editing that batocera-boot.conf file to “kill bluetooth” will only impact the built-in transceiver on the Pi4 board, correct? I still want to use an external Bluetooth USB dongle to work around the problems I’m having.

That said, I’ll also have to check the /boot/boot/config.txt file thing to ensure that motherboard Bluetooth is being disabled…I already did an edit to disable it once in /boot/config.txt.

Atari

That I’m not sure about. In regular Raspbian I just use rfkill disable bluetooth so I’m not truly knowledgeable on how much that actually disables.

mickelsn

OK, looks like things worked as I wanted. I just added dtoverlay=disable-bt to the /boot/config.txt file and it killed the onboard transceiver as expected. Running rfkill at the command line shows only the wireless LAN as active.

One thing to note - the Batocera install (EmulationStation) still acted like it could search for and pair with controllers, but every attempt to do so failed. Would have liked for EmulationStation to recognize that Bluetooth was disabled and not enabled those items in the menu, but whatever.

Then I connected (hot-plugged) an external Bluetooth dongle via USB. Batocera/EmulationStation still wouldn’t recognize Bluetooth and pair to a controller, but once I did a full system reboot everything worked as expected. I haven’t exhaustively tested to confirm the lag issues are gone, but it’s likely that they are given how quickly pairing went with the external dongle…

Atari

mickelsn I believe that is by designed, if it was coded to ‘recognise’ and disable the option in the menu, I’m sure we’d have thousands more support tickets of users complaining about “Where is bluetooth menu?!!?!???!” (whether they would be legitimate or not is up for debate).

Do let me know if that eliminates the lag issue, and if so I’ll compile that information into the wiki.