I'm trying to write a script that boots my device into FEL mode (device boots from USB OTG port). Normally, this is only possible by pushing a physical "flash" button on the PCBA during boot up. Here is the boot flow for the device:
boot-> check fel key pressed (yes)--> FEL mode (boot from USB OTG)
\
(no) \
\-------> 1) try to boot from SMHC0 (SD card)
2) try to boot from SMHC2 (eMMC)
3) try to boot from SPI0 (SPI NOR Flash)
4) FEL mode (boot from USB OTG)
So if the Boot ROM doesn't find any valid boot image, it will automatically enter FEL mode (see more about this here: https://linux-sunxi.org/FEL#Triggering_FEL_mode). My idea is to write a script to intentionally corrupt the bootloader or the boot image so that the Boot ROM will fail and fall through to FEL mode. Then, after a reboot, I should enter FEL mode.
I get that this is probably undesirable in many ways. But is this possible? How would I go about corrupting the bootloader and/or boot image so that the Boot ROM fails?
Note: I don't have access to a serial console and there is no way to use an SD card image.
