Address Collisions When Four Parts Share One I2C Bus
Resolve four-part I2C address collisions using 4-state pin strapping, quad-channel switches, or address translation ICs based on BOM cost and driver complexity.
4-State Address Pin
Electrical Configuration
An integrated circuit pin configured to detect multiple logic states allows a single physical terminal to select among several communication addresses. By connecting a 4-state address pin to ground, to the supply line, or to one of two external resistive dividers, a host device determines the unique hardware identifier of a sensor.
Address Allocation
Internal decoding circuitry samples the voltage at startup to assign the peripheral to a specific command channel. This 4-state address pin replaces two standard binary pins, which reduces the package size and lowers the overall system cost of the sensor. Designers deploy this scheme when several identical sensors must share a single bus.
Voltage Division
External resistors connected to the pin must maintain tight tolerances to prevent incorrect state detection. A typical arrangement utilizes a fifty percent ratio of the supply voltage, where a ten percent deviation can lead to an address conflict on the bus. Noise on the supply rail can shift the sampled level during the initialization phase.
Startup Timing
The internal analog to digital converter or window comparator measures the pin level only during the power-on reset sequence. After this initial check, the state is locked to prevent subsequent fluctuations from altering the communication path.