Errata

Applies to BL702, BL704 and BL706

Issues with running image loaded by BootROM

For some reason, BOOTROM_RUN_IMAGE (0x1A) command in BootROM, doesn’t work properly, and because of it, eflash_loader have issues with initializing USB (so sometimes in Windows, the UART driver freeze, so it can’t communicate with eflash_loader). (NOTE: This is observation, other issues are not known yet)

To workaround this, there are three registers set, via BOOTROM_WRITE_MEM (0x50) command in BootROM:

0x4000F100 => 0x4E424845 (This sets RSV0 to HBN_STATUS_ENTER_FLAG in Deep Sleep Control (Hibernate) core, in SDK it is used as set STATUS flag. (gamiee: My guess is that BootROM read this after CPU reset?))
0x4000F104 => 0x22010000 (This sets RSV1 register in Hibernate core, in SDK it is used as WakeUp Address, and exactly we write the launch address, where eflash_loader should be) (gamiee: those reserved registers in HBN does nothing at all, just those values are preserved between CPU Resets)
0x40000018 => 0x00000002 (This sets swrst_cfg2 register in Global Control Register, enabling register reg_ctrl_cpu_reset)

You can find this workaround in bflb_mcu_tool in file bflb_mcu_tool/libs/bl702/chiptype_patch.py.