Definition
The I2C bus (Inter-Integrated Circuit, pronounced "I-squared-C") is a two-wire serial bus that lets one controller talk to many low-speed peripheral chips over a shared pair of lines: a data line (SDA) and a clock line (SCL). Each device on the bus has a unique address, so a single controller can reach dozens of sensors and memory chips with just two signals. In Antminers the Zynq control board uses I2C to reach the small EEPROM on each hashboard.
The hashboard EEPROM link
Every Antminer hashboard carries a tiny I2C EEPROM — commonly a Microchip AT24C-series part — that stores the board's serial number, chip count, calibration data, voltage settings, and frequency profiles. When the control board boots and initializes a hashboard, it reads this EEPROM over I2C first. If that read fails or returns invalid data, the firmware reports an EEPROM error and refuses to bring the board online.
Why it matters for repair
Many "dead hashboard" symptoms trace back to a broken I2C path: a cracked solder joint on SDA/SCL, a damaged EEPROM, or a corrupted EEPROM image. Diagnosing these means confirming the bus reaches the chip and that the stored data is valid. Re-writing a known-good EEPROM image is a routine board-level repair.
I2C is one of the control board's several serial interfaces; for the serial console used in boot diagnostics, see UART, and for the controller running the bus, see Zynq SoC.
In Simple Terms
The I2C bus (Inter-Integrated Circuit, pronounced “I-squared-C”) is a two-wire serial bus that lets one controller talk to many low-speed peripheral chips over a shared…