one mystery I2C adress

I have a PCB running on an atmega328 and it has 4 I2C devices; a DS1803 digital potentiometer at 0x28 a DS3231 RTC module at 0x68 an MCP23017 I/O expander at 0x25 an I2C LCD at 0x27

I ran the I2C scanner code from rob tillaart and I can find five adresses. The unknown adress is 0x57 and I dont what it is.

Could this be the internal EEPROM or something? I also have an SD card slot with Sd card but that one is running on the SPI bus

Why don't you scan with each of the 4 devices one at a time... or even with none of them? That might narrow it down.

Is the internal EEPROM I2C?, or if it is, it never gives me an extra address anyway.

Googling I2C 0x57 turns up multiple references to RTC modules with an on-board EEPROM at address 0x57 - could yours have that?

JimboZA: Why don't you scan with each of the 4 devices one at a time... or even with none of them? That might narrow it down.

I cant, all devices are soldered on my PCB

DrAzzy: Googling I2C 0x57 turns up multiple references to RTC modules with an on-board EEPROM at address 0x57 - could yours have that?

I think so, I have an extra one lying arround. I need to try that I think

I guess you use something like a TinyRTC module? These indeed have an I2C EEPROM onboard.

bask185: a DS3231 RTC module at 0x68

You said "module".

Count the chips.