How to enter FEL on PB618, backup, restore emmc?

[Soupborsh]

I would like to enter FEL mode on Pocketbook 618 but I do not know how. I tried this mutiple times and pressing different buttons but it didn't work, device booted normally.

I am learing about Linux, programming and I would like to use normal GNU/Linux distro on PB618 such as PostmarketOS, Debian and etc. To start experimenting and learn I need to somehow enter FEL mode. Also I want to backup emmc and restore it if I mess with it and device would not boot into OS, I do not know how to do it.

Here is what I tried to enter FEL:

• Turn off while connected to pc, hold button and press power button
• same but hold power button for 2 sec and then quickly click it >3 times
• flash sunxi fel image to external SD card and place it in PB618(I did it from termux and SD card is 128GB, Pocketbook can see it using fdisk -l but cannot mount and does not see in library even with normal fat32 with normal files and no fel image)

Do you know how to enter FEL mode? I can disassemble it if needed.

I added this to soc_info.c in sunxi tools:

Spoiler:

},{
		.soc_id       = 0x1699, /* Allwinner B288 */
		.name         = "B288",
		.scratch_addr = 0x1000,
		.thunk_addr   = 0xA200, .thunk_size = 0x200,
		.swap_buffers = a10_a13_a20_sram_swap_buffers,
		.sid_base     = 0x01C14000,

My PB618 is jailbroken thanks to pbjb.