They appear in the NON-OS SDK file eagle.rom.addr.v6.ld:
The functions are: ets_printf, ets_putc, SPIRead, and SPIWrite.
The last two are very important since they are required for bootloader operation. The two "ets_" functions are for exporting debug data during the boot process.
I don't use the NON-OS SDK since I prefer the RTOS version.
To my surprise, those functions don't exist in the RTOS SDK.
Can someone tell me the equivalent function name in the RTOS_SDK?
Why would common low-level functions be in one SDK and not the other?