Add customisable EEPROM driver selection (#7274)

- uprintf -> dprintf
- Fix atsam "vendor" eeprom.
- Bump Kinetis K20x to 64 bytes, too.
- Rollback Kinetis to 32 bytes as partitioning can only be done once. Add warning about changing the value.
- Change RAM-backed "fake" EEPROM implementations to match eeconfig's current usage.
- Add 24LC128 by request.

1 files changed, 50 insertions, 0 deletions

diff --git a/docs/eeprom_driver.md b/docs/eeprom_driver.md
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+# 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`    | 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. 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 = transient` | Fake EEPROM driver -- supports reading/writing to RAM, and will be discarded when power is lost.
+
+## Vendor Driver Configuration
+
+No configurable options are available.
+
+## I2C 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
+
+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:
+
+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>
+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`.
+
+## Transient 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`.