EEPROM

The Arduino EEPROM API over the option-byte area, for the CH32V003. More...

Classes
class	EEPROMClass
	26 bytes of emulated EEPROM in the option-byte area, worked on in a RAM copy and written by commit() (see EEPROM). More...

Variables
EEPROMClass	EEPROM
	The emulated EEPROM.

Detailed Description

The Arduino EEPROM API over the option-byte area, for the CH32V003.

On the CHGame board (CH32X035) it does not save: commit() writes nothing and returns false.

Note

Saving on the CHGame board? Use the CHGame library's save:: functions: a CRC-checked record of up to 244 bytes in the top two pages of the application flash, shared by every game (each tells its records apart by its own magic), which survives power cuts and re-uploads.

What the library does on the chip it was written for, the CH32V003:

• 26 bytes, copied into a buffer on the heap by begin(). Bytes 0 and 1 are the user option bytes Data0 and Data1; bytes 2-25 are kept as half-words (each value with its inverse) at 0x1FFFF810-0x1FFFF83F, after the 16 bytes of the option-byte block (OB_BASE, 0x1FFFF800).
• read(), write(), get(), put(), erase() and [] work on that buffer. Nothing reaches flash until commit() (or end()).
• commit() erases the whole option-byte area, writes back the read protection (RDPR), user (USER) and write protection (WRPR0-3) words it copied just before, then Data0, Data1 and every byte that is not 0xFF. It does not check what it wrote.

On the CH32X035 that commit() is switched off, and a sketch that includes this header gets a compiler message saying so. The chip's option-byte block is the 16 bytes alone, and WCH's CH32X035 library programs it only as one fast-programmed page, never a half-word at a time as above. A write that did not take after the erase would leave the chip read-protected (removing that with the factory ISP erases the whole flash, bootloader included) or with its user options changed (on this board they keep PB7, SELECT, from being the reset pin). So on this chip begin() reads Data0 and Data1 and sets bytes 2-25 to 0xFF, everything works on the RAM copy as usual, and commit() returns false without writing. Nothing survives a reset.

Variable Documentation

EEPROM

EEPROMClass EEPROM

extern

The emulated EEPROM.

Call EEPROM.begin() first.