I've been patiently trying to upgrade the firmware on this Anet A8 and reached a dead end.
First I installed a bootloader by downloading Audrino software, downloading the board definitions, copying files from the board definitions into the Audrino directory, selected the optibootloader, installed a USBasp driver, made sure to select ATmega1284p, and installed the bootloader.
At this point it seemed to upload well, however, I was no longer able to communicate with the Anet board. Assuming it has now switched to the USB, I've tried connecting it to the USB and I'm unable to see it. Currently it's out of the printer, so maybe it needs power instead of trying to get it from the USB port.
After I went to build Marlin 2.0.9.1 in Visual Studio Code, and, per the tutorial, I need to download Config 2.0.8.2 and copy three files _Statusscreen, Configuration, Configuration_adv, into the Marlin firmware folder.
After following some basic steps in Visual Studio Code, I went to build it, and, unlike the tutorial, I have two environments: sanguino1284p and sanguino1284p_optimized.
I don't know what the difference is, or what they mean, but I chose to build the standard (i.e. no optimized) and got a compiling error that configuration.adv.h is for an old version of Marlin. I then tried the optimized and got the same compiling error.
I'm uncertain why I'm getting this because I'm using the latest and greatest version of Marlin and the latest version of the configuration files.
Also, I don't know why I can't communicate with the board after installing the bootloader (I'm hoping it just needs external power).