Janus

what it is

Janus is an Android app that bridges your phone's media to LlizardOS. Named for the Roman god of doorways and transitions - the deity with two faces looking in opposite directions - it serves as the gateway between devices.

It runs a Bluetooth GATT server, exposing media information and accepting control commands. The phone becomes the source, the car thing becomes the display.

how it works

1 Janus starts a GATT server on your phone

2 LlizardOS connects as a GATT client

3 Media metadata flows to the car thing

4 Control commands flow back to the phone

gatt characteristics

track title

0x2001

current track name, read/notify

artist

0x2002

artist name, read/notify

album art

0x2003

compressed image data, read

playback state

0x2004

play/pause/position, read/notify

controls

0x2010

play, pause, skip, write

volume

0x2011

volume level, read/write

built with

kotlin android bluetooth le gatt server media3 room db

view on github →

the other faces

Janus serves LlizardOS through Mercury - the Go BLE client on the CarThing that receives media state and sends back playback commands.

see Mercury → see Llizard → see LlizardOS →