On Wed, Sep 16, 2020 at 09:40 AM, George Cushing wrote:
Does the BluePill boot from the system memory or the DS3231's flash?. Could the DS3231 be replaced with SD flash?The Bluepill, and all other microcontrollers that OnStep uses, load their program from flash memory.
Never from EEPROM.
Loading from and SD card is possible provided that there are enough pins for it (which the Blue Pill does not have).
Many 3D printer boards update their firmware over and SD card. They provide a custom bootloader on the
microcontrollre that looks for a specific file name on the SD card, and if it is there, it updates its internal flash
from that file.
Not practical for OnStep at present ...
No, an SD flash cannot replace the DS3231 EEPROM because they are for different things (parameters vs. program code).