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- # EEPROM Driver Configuration :id=eeprom-driver-configuration
-
- The EEPROM driver can be swapped out depending on the needs of the keyboard, or whether extra hardware is present.
-
- Driver | Description
- -----------------------------------|---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
- `EEPROM_DRIVER = vendor` (default) | Uses the on-chip driver provided by the chip manufacturer. For AVR, this is provided by avr-libc. This is supported on ARM for a subset of chips -- STM32F3xx, STM32F1xx, and STM32F072xB will be emulated by writing to flash. STM32L0xx and STM32L1xx will use the onboard dedicated true EEPROM. Other chips will generally act as "transient" below.
- `EEPROM_DRIVER = i2c` | Supports writing to I2C-based 24xx EEPROM chips. See the driver section below.
- `EEPROM_DRIVER = spi` | Supports writing to SPI-based 25xx EEPROM chips. See the driver section below.
- `EEPROM_DRIVER = transient` | Fake EEPROM driver -- supports reading/writing to RAM, and will be discarded when power is lost.
-
- ## Vendor Driver Configuration :id=vendor-eeprom-driver-configuration
-
- #### STM32 L0/L1 Configuration :id=stm32l0l1-eeprom-driver-configuration
-
- !> Resetting EEPROM using an STM32L0/L1 device takes up to 1 second for every 1kB of internal EEPROM used.
-
- `config.h` override | Description | Default Value
- ------------------------------------|--------------------------------------------------------------------------------------------------------------------------|----------------------------------------------------------------------------
- `#define STM32_ONBOARD_EEPROM_SIZE` | The size of the EEPROM to use, in bytes. Erase times can be high, so it's configurable here, if not using the default value. | Minimum required to cover base _eeconfig_ data, or `1024` if VIA is enabled.
-
- ## I2C Driver Configuration :id=i2c-eeprom-driver-configuration
-
- Currently QMK supports 24xx-series chips over I2C. As such, requires a working i2c_master driver configuration. You can override the driver configuration via your config.h:
-
- `config.h` override | Description | Default Value
- ------------------------------------------- | ----------------------------------------------------------------------------------- | ------------------------------------
- `#define EXTERNAL_EEPROM_I2C_BASE_ADDRESS` | Base I2C address for the EEPROM -- shifted left by 1 as per i2c_master requirements | 0b10100000
- `#define EXTERNAL_EEPROM_I2C_ADDRESS(addr)` | Calculated I2C address for the EEPROM | `(EXTERNAL_EEPROM_I2C_BASE_ADDRESS)`
- `#define EXTERNAL_EEPROM_BYTE_COUNT` | Total size of the EEPROM in bytes | 8192
- `#define EXTERNAL_EEPROM_PAGE_SIZE` | Page size of the EEPROM in bytes, as specified in the datasheet | 32
- `#define EXTERNAL_EEPROM_ADDRESS_SIZE` | The number of bytes to transmit for the memory location within the EEPROM | 2
- `#define EXTERNAL_EEPROM_WRITE_TIME` | Write cycle time of the EEPROM, as specified in the datasheet | 5
- `#define EXTERNAL_EEPROM_WP_PIN` | If defined the WP pin will be toggled appropriately when writing to the EEPROM. | _none_
-
- Some I2C EEPROM manufacturers explicitly recommend against hardcoding the WP pin to ground. This is in order to protect the eeprom memory content during power-up/power-down/brown-out conditions at low voltage where the eeprom is still operational, but the i2c master output might be unpredictable. If a WP pin is configured, then having an external pull-up on the WP pin is recommended.
-
- Default values and extended descriptions can be found in `drivers/eeprom/eeprom_i2c.h`.
-
- Alternatively, there are pre-defined hardware configurations for available chips/modules:
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- Module | Equivalent `#define` | Source
- -----------------|---------------------------------|------------------------------------------
- CAT24C512 EEPROM | `#define EEPROM_I2C_CAT24C512` | <https://www.sparkfun.com/products/14764>
- RM24C512C EEPROM | `#define EEPROM_I2C_RM24C512C` | <https://www.sparkfun.com/products/14764>
- 24LC64 EEPROM | `#define EEPROM_I2C_24LC64` | <https://www.microchip.com/wwwproducts/en/24LC64>
- 24LC128 EEPROM | `#define EEPROM_I2C_24LC128` | <https://www.microchip.com/wwwproducts/en/24LC128>
- 24LC256 EEPROM | `#define EEPROM_I2C_24LC256` | <https://www.sparkfun.com/products/525>
- MB85RC256V FRAM | `#define EEPROM_I2C_MB85RC256V` | <https://www.adafruit.com/product/1895>
-
- ?> If you find that the EEPROM is not cooperating, ensure you've correctly shifted up your EEPROM address by 1. For example, the datasheet might state the address as `0b01010000` -- the correct value of `EXTERNAL_EEPROM_I2C_BASE_ADDRESS` needs to be `0b10100000`.
-
- ## SPI Driver Configuration :id=spi-eeprom-driver-configuration
-
- Currently QMK supports 25xx-series chips over SPI. As such, requires a working spi_master driver configuration. You can override the driver configuration via your config.h:
-
- `config.h` override | Description | Default Value
- -----------------------------------------------|--------------------------------------------------------------------------------------|--------------
- `#define EXTERNAL_EEPROM_SPI_SLAVE_SELECT_PIN` | SPI Slave select pin in order to inform that the EEPROM is currently being addressed | _none_
- `#define EXTERNAL_EEPROM_SPI_CLOCK_DIVISOR` | Clock divisor used to divide the peripheral clock to derive the SPI frequency | `64`
- `#define EXTERNAL_EEPROM_BYTE_COUNT` | Total size of the EEPROM in bytes | 8192
- `#define EXTERNAL_EEPROM_PAGE_SIZE` | Page size of the EEPROM in bytes, as specified in the datasheet | 32
- `#define EXTERNAL_EEPROM_ADDRESS_SIZE` | The number of bytes to transmit for the memory location within the EEPROM | 2
-
- !> There's no way to determine if there is an SPI EEPROM actually responding. Generally, this will result in reads of nothing but zero.
-
- ## Transient Driver configuration :id=transient-eeprom-driver-configuration
-
- The only configurable item for the transient EEPROM driver is its size:
-
- `config.h` override | Description | Default Value
- ------------------------------- | ----------------------------------------- | -------------
- `#define TRANSIENT_EEPROM_SIZE` | Total size of the EEPROM storage in bytes | 64
-
- Default values and extended descriptions can be found in `drivers/eeprom/eeprom_transient.h`.
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