I was looking online and saw something about the tone board able to use a mini lcd screen and and a 8 channel expansion, are the 8 channel expansions good for audio inputs and what kind of expansion or outputs or inputs are possible, and for the screen connector, is it possible to to use a mini 3.5 inch screen as a secondary screen on the vim
You can connect mini LCD screen to the computer you use to play your music, just beside of of the Tone Board. The Tone Board has an OLED connector (see e.g OLED Connector? ), but that is just an extension (pass-trhough) from the VIM GPIO connector, it is not connected to any component on the Tone Board itself. It means it is just the same as connecting it to the VIM independently. (However, Khadas does not currently offer any display ready to connected to the connector.) The VIM/computer can than be programmed to display just anything on the OLED. Of course it can be used as a secondary display to whatever else… but that has nothing to do with the Tone Board - it is just another display connected to the VIM/computer.
I wondered whether an OLED display could be connected and also controlled directly by the Tone Board itself (see Indicating the sample rate and format ). This seems to be possible in theory through the extension connector of the TB, where its I2C bus is available, but it would be necessary to have the source code of the TB firmware available and to extend it by the display driver for your display (which is more difficult than connecting it to the VIM/computer). The TB firmware is not currently available, however. And the TB itself could only indicate sample rate and data format, nothing else. You can do much more by controlling it by the computer, as mentioned above.
The expansion connector offers additional I2S channels output from the XMOS controller used to convert data from the USB (and SPDIF) input to the I2S bus. So, in theory, you can connect 4 more DAC boards (either 4 Tone Boards or 4 other boards) to the extension connector and get up to 8 channels audio output (analog) from the single USB input. However, there is no documentation nor description how to actually do it, Khadas does not currently offer any expansion DAC units itself and nobody else managed to do it yet (as long as reported by this forum).
Maybe Khadas could tell you more…?
Yep, it will works, but absolutely will need some coding work there
Yes, that is why I asked about the possibility to open source your firmware. It would need some coding to drive the OLED, but it would need much much more coding to develop all of your firmware from the scratch again