EEPROM_module

[jlamperez]

EEPROM module

This module also contains a .h and .c file.

The eeprom.h file has EEPROM_VERSION to define the EEPROM version. This value should be changed in code whenever changes to the OpenServo registers would cause the data stored in EEPROM to be incompatible from one version of the OpenServo firmware to the next version of the OpenServo firmware.

Functions defined in eeprom.c file:

• *eeprom_checksum(const uint8_t buffer, size_t size, uint8_t sum):** Adds the buffer to the checksum(sum) and return the updated checksum.

While there are bytes in the buffer, they are added to the sum and the size value is decreased.

while (size)
    {
        sum += *buffer;

        ++buffer;
        --size;
    }

• eeprom_erase(): Erase the entire EEPROM The uint8_t buffer[16] content is clear to the 0xFF content.

memset(buffer, 0xFF, sizeof(buffer));

Loop over the EEPROM and write the buffer to the EEPROM block.

for (i = 0; i < E2END; i += sizeof(buffer))
    {
        eeprom_write_block(buffer, (void *) i, sizeof(buffer));
    }

• eeprom_restore_registers(): Restore registers from eeprom. Read the EEPROM first two bytes Using eeprom api function eeprom_read_block

eeprom_read_block(&header[0], (void *) 0, 2);

If the EEPROM version does not match return error.

if (header[0] != EEPROM_VERSION) return 0;

Read the registers from EEPROM

eeprom_read_block(&registers[MIN_WRITE_PROTECT_REGISTER], (void *) 2, WRITE_PROTECT_REGISTER_COUNT + REDIRECT_REGISTER_COUNT);

If the checksum does not match throw an error else success

if (header[1] != eeprom_checksum(&registers[MIN_WRITE_PROTECT_REGISTER], WRITE_PROTECT_REGISTER_COUNT + REDIRECT_REGISTER_COUNT, EEPROM_VERSION)) return 0;

• eeprom_save_registers(): Save the registers to the EEPROM. Fill the EEPROM header and write the values to the EEPROM

header[0] = EEPROM_VERSION;
header[1] = eeprom_checksum(&registers[MIN_WRITE_PROTECT_REGISTER], WRITE_PROTECT_REGISTER_COUNT + REDIRECT_REGISTER_COUNT, EEPROM_VERSION);

eeprom_write_block(&header[0], (void *) 0, 2);
eeprom_write_block(&registers[MIN_WRITE_PROTECT_REGISTER], (void *) 2, WRITE_PROTECT_REGISTER_COUNT + REDIRECT_REGISTER_COUNT);

Overview of ATmega168 Flash/EEPROM Map

Page size = 128 bytes

Page	Address	Type
00	0000-007F	Flash
...
77	3B80-3BFF	Flash
78	3C00-3C7F	Flash (bootloader)
...
7F	3FC0-3FFF	Flash (bootloader)
80	4000-407F	EEPROM
...
83	4180-41FF	EEPROM

Flash(App) size -> 128 pages.128bytes = 15360bytes = 15KB Flash(Bootloader) size -> 8.128 = 1024 bytes = 1KB EEPROM -> 4.128 = 512bytes

Overview of ATmega328P Flash/EEPROM Map

Page size = 128 bytes

Page	Address	Type
00	0000-007F	Flash
...
		Flash
F8	7C00-7C7F	Flash (bootloader)
...
100	7F80-7FFF	Flash (bootloader)
101	8000-807F	EEPROM
...
108	8380-83FF	EEPROM

Flash(App) size -> 248 pages.128bytes = 31744bytes = 31KB Flash(Bootloader) size -> 8.128 = 1024 bytes = 1KB EEPROM -> 8.128 = 1024bytes Descritpion The AVR flash memory is divided into two sections namely the application section and the Boot-Loader section (BLS). In case of the ATMEGA16 it has 16 KB of flash memory of which the 15KB is application section and the remaining 1KB is BLS. The memory architecture of the ATMEGA16 is shown in the following figure: The code for both the BLS and application section can be written as normally does and there is no much difference. The only thing to be careful about is the size of the code binary. It should not be more than 1KB, otherwise it won’t be able to code programmed into the BLS.

How To load Application from EEPROM Steps with which binary of a code are read from the EEPROM memory and flashing the same into the flash memory is represented pictorially in the following:

• Step: 1 Erase the flash page which is about to write into
• Step: 2 Store the binaries in a temporary buffer before write into a flash page
• Step: 3 Program the filled temporary buffer into the already erased flash page