fmc: document fru eeprom programming via ch341a

add programming instructions to fmc_basic_peripheral and fmc_sdram
readme covering wiring, write/verify commands, and the 238-byte
file vs 256-byte padded image quirk.

Signed-off-by: Huang Rui <vowstar@gmail.com>

Author: vowstar

fmc_basic_peripheral/README.md

@@ -40,3 +40,17 @@ If you need to generate complete production data,
 ```bash
 cmake --build build --target production
 ```
+
+## Program the FRU EEPROM
+
+Use a CH341A USB-to-I2C adapter (PID `1a86:5512`, EPP/MEM/I2C mode) with
+[ch341eeprom](https://github.com/commandtab/ch341eeprom). Wire `SDA`, `SCL`,
+`VCC` (3.3V) and `GND` to the on-board M24C02, and pull `WP` to GND.
+
+```bash
+ch341eeprom -v -s 24c02 -w build/fmc_fru_eeprom.bin
+ch341eeprom -v -s 24c02 -V build/fmc_fru_eeprom.bin
+```
+
+The verifier reports a mismatch at offset 238 because the FRU image is 238
+bytes while the EEPROM is padded to 256 — the FRU data itself is correct.

fmc_sdram/README.md

@@ -41,3 +41,17 @@ If you need to generate complete production data,
 ```bash
 cmake --build build --target production
 ```
+
+## Program the FRU EEPROM
+
+Use a CH341A USB-to-I2C adapter (PID `1a86:5512`, EPP/MEM/I2C mode) with
+[ch341eeprom](https://github.com/commandtab/ch341eeprom). Wire `SDA`, `SCL`,
+`VCC` (3.3V) and `GND` to the on-board M24C02, and pull `WP` to GND.
+
+```bash
+ch341eeprom -v -s 24c02 -w build/fmc_fru_eeprom.bin
+ch341eeprom -v -s 24c02 -V build/fmc_fru_eeprom.bin
+```
+
+The verifier reports a mismatch at offset 238 because the FRU image is 238
+bytes while the EEPROM is padded to 256 — the FRU data itself is correct.