How to update the firmware of BTR13?

Online upgrade：
Set the BTR13 to the BT mode and connect to the mobile phone via Bluetooth. Download the Fiio Control App on your phone and connect the BTR13. On the BTR13 page, click the settings pattern in the upper right corner, find "Firmware Upgrade", find "Online Upgrade" and click it. If BTR13 has available Bluetooth firmware, a pop-up window will prompt you for the new version. Click OK to upgrade.

Local upgrade:
1. Import the "BTR13_Vxxx.bin" firmware into the mobile phone;
2.Set the BTR13 to the BT mode and connect to the mobile phone via Bluetooth. Download the Fiio Control App on your phone and connect the BTR13. On the BTR13 page, click the settings pattern in the upper right corner, find "Firmware Upgrade", find "Local Upgrade", select the firmware imported to the phone, and start upgrading the firmware.
Note: During the firmware upgrade process, please do not leave the upgrade interface, otherwise the upgrade may fail! The upgrade may take a long time, please be patient. If the upgrade fails, you can try again.