How can I write some data to eMMC on board without fastboot?
with usb-c
You can write eMMC partition (e.g. /dev/mmcblk0p1) simply with dd (or cat). but the board needs to be booted. Can you clarify why you can not use fastboot?
I know that I can do that when I boot board 
But I am just asking if there is another options without booting board with some other tools
