I can't find so much information about this controller if it doesn't have an SD card slot then you can maybe flash it through SSH flashing or USB flashing using the provided firmware from Canaan.
I search and try to find some information on Google and found one thread here on the forum related to this controller but it has an SD card slot but he is trying to flash the controller without an SD card.
You can check this thread below and maybe you can get some information on how to flash it without an SD card.
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https://bitcointalk.org/index.php?topic=5115034.0