Unlocking the amlogic control board to be able to downgrade the stock firmware date and installing the “VNISH” firmware
AMLOGIC control boards running stock firmware released after September 2025, the ability to downgrade firmware via SD card has been disabled. This tutorial describes a method to re-enable that capability. Before starting, make sure you have the following: 
Perform the following steps: Connect the adapter to the computer. Identify the assigned COM port number (in our case, COM7) 
Identify the UART pins on the control board. Connect the USB-to-UART adapter to the control board according to the following wiring scheme: GND → GND, RXD → LINUX_TX, TXD → LINUX_RX
- AML control board and a 12V power supply
- A computer or laptop with Windows installed
- Any USB-to-UART adapter with drivers installed (in our case, Silicon Labs CP2102)
- A terminal program (in our case, PuTTY) to connect to the control board and send commands
Perform the following steps: Connect the adapter to the computer. Identify the assigned COM port number (in our case, COM7) Identify the UART pins on the control board. Connect the USB-to-UART adapter to the control board according to the following wiring scheme: GND → GND, RXD → LINUX_TX, TXD → LINUX_RX 
Open the PuTTY terminal window. Specify the correct COM port number and set the data transfer rate to 115200. Leave all other parameters as default. Click “Open” 
At this stage, you can check that the connections are correct. After powering the control board, the device boot log should appear in the terminal window 
Turn off the control board and short the JP2 jumper using tweezers or a screwdriver. 
Make sure the terminal window is active Power on the control board. As soon as the first boot line appears in the terminal, quickly release the JP2 jumper and press the space bar several times in the active terminal window. After these steps, the ENV loading process should begin. If this does not happen (which is acceptable), perform the following steps: 
Enter the command: setenv bitmain_usb_switch 1 This command enables the USB port, press enter. 
Next, enter: saveenv This command saves the setting, press enter 
Reboot the control board. After this, you can downgrade the current firmware version using an SD image, which will then allow you to install the Vnish firmware. If you cannot unlock the port and see this window, enter the commands in the following order: 
At this stage, you can check that the connections are correct. After powering the control board, the device boot log should appear in the terminal window Turn off the control board and short the JP2 jumper using tweezers or a screwdriver. Make sure the terminal window is active Power on the control board. As soon as the first boot line appears in the terminal, quickly release the JP2 jumper and press the space bar several times in the active terminal window. After these steps, the ENV loading process should begin. If this does not happen (which is acceptable), perform the following steps: - Turn off the control board and turn it back on. Briefly short the JP1 or JP2 jumpers a couple of times. This should force the board into U-Boot boot mode.
Enter the command: setenv bitmain_usb_switch 1 This command enables the USB port, press enter. Next, enter: saveenv This command saves the setting, press enter Reboot the control board. After this, you can downgrade the current firmware version using an SD image, which will then allow you to install the Vnish firmware. If you cannot unlock the port and see this window, enter the commands in the following order: - saveenv
- setenv bitmain_usb_switch 1
- saveenv