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March 6, 2026 23:43
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eeprom size detect with mirror method
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| #include <Wire.h> | |
| #define EEPROM_I2C_ADDRESS 0x50 | |
| void setup() { | |
| Serial.begin(9600); | |
| delay(1000); | |
| // init i2c bus | |
| Wire.begin(); | |
| Serial.println("=== EEPROM Size Detector (Mirror/Wrap-around Method) ==="); | |
| // save original byte at address 0 | |
| byte original = readEEPROM(0); | |
| Serial.print("Original byte at address 0: 0x"); | |
| Serial.println(original, HEX); | |
| // write a unique test patter | |
| writeEEPROM(0, 0xA5); | |
| unsigned long detectedSize = 0; | |
| const unsigned long MAX_CHECK = 131072UL; // 128 KB — safety cap ?? | |
| // test typical power-of-2 sizes where mirroring would show up | |
| for (unsigned long addr = 128; addr <= MAX_CHECK; addr *= 2) { | |
| if (readEEPROM(addr) == 0xA5) { | |
| detectedSize = addr; | |
| break; | |
| } | |
| } | |
| // restore original value | |
| writeEEPROM(0, original); | |
| if (detectedSize > 0) { | |
| Serial.print("Detected EEPROM size: "); | |
| Serial.print(detectedSize); | |
| Serial.print(" bytes ("); | |
| Serial.print(detectedSize / 1024UL); | |
| Serial.println(" KB)"); | |
| Serial.println("This is the most common result for 24xx series chips."); | |
| } else { | |
| Serial.println("No mirroring detected up to 128 KB."); | |
| Serial.println("Check connections, I2C address, or try a higher MAX_CHECK."); | |
| } | |
| Serial.println("\nDone. Your data at address 0 is restored."); | |
| } | |
| void loop() { | |
| // null | |
| } | |
| // write 1 byte | |
| void writeEEPROM(unsigned int addr, byte data) { | |
| Wire.beginTransmission(EEPROM_I2C_ADDRESS); | |
| Wire.write((byte)(addr >> 8)); // MSB | |
| Wire.write((byte)(addr & 0xFF)); // LSB | |
| Wire.write(data); | |
| Wire.endTransmission(); | |
| delay(6); // wait for internal write cycle | |
| } | |
| // read one byte | |
| byte readEEPROM(unsigned int addr) { | |
| Wire.beginTransmission(EEPROM_I2C_ADDRESS); | |
| Wire.write((byte)(addr >> 8)); // MSB | |
| Wire.write((byte)(addr & 0xFF)); // LSB | |
| Wire.endTransmission(); | |
| Wire.requestFrom(EEPROM_I2C_ADDRESS, (byte)1); | |
| if (Wire.available()) { | |
| return Wire.read(); | |
| } | |
| return 0xFF; | |
| } |
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