Flowcode Support Board

Is it possible to expand MCU Flash memory with external EEPROM?

If you mean use EEPROM to store additional program instructions. In theory this could be done but it would likely require a complex routine to fetch the instructions from the EEPROM and then a) parse the instructions one by one or b) write them onto a section of the internal flash to be executed in the normal manner. Both of these would likely be fairly slow and option b would likely burn out the internal flash memory after 10,000 to 100,000 erase/write cycles.