What is it?

The PCA9545A is a 4-channel I2C (Inter-Integrated Circuit) multiplexer designed to allow a single I2C bus to communicate with multiple devices with SAME I2C addresses, thus resolving any I2C address conflicts. It provides an efficient solution for connecting multiple I2C devices to a microcontroller or other host system, and enables the communication with each individual device in a controlled and timely manner. The PCA9545A works by selecting one of the four channels through a control register accessible via the I2C interface.

The PCA9545A is designed to operate over a wide range of supply voltages, from 2.3V to 5.5V, and supports fast-mode and standard-mode I2C communication. It features a low standby current consumption, making it suitable for use in battery-powered devices.

Overall, the PCA9545A I2C multiplexer provides a simple and effective way to expand the capabilities of an I2C bus and to interface multiple devices with same addresses to a single host system.

NOTE: The labeling on the board silkscreen is jammed, so here are the pinouts:

Top Row: ~INT0, SD0, SC0, ~INT, SDA, SCL, ~RST, GND, VCC Bottom Row: SC1, SD1, ~INT1, SC2, SD2, ~INT2, SC3, SD3, ~INT3

Use the following Arduino code to select between the 4 channels

define PCAADDR 0x70

void SelectChannel(uint8_t i) { if (i > 4) return;

Wire.beginTransmission(PCAADDR); Wire.write(1 << i); Wire.endTransmission(); }

For example, after you run SelectChannel(2), the mux will route the SCL and SDA signals to SC2 and SD2.