ESPMUSE Proto Schematic

Is there a schematic available for the ESPMUSE Proto? I am using the board to retrofit a Bluetooth solar-powered speaker-in-a-rock for my front yard. I am removing the Bluetooth control board and replacing with the ESPMUSE Proto. I would like to use the existing solar panel and charger with the ESPMUSE Proto. Understanding the power and charger circuitry will be helpful.

Thank you.