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PCA9548A is an eight-channel (bidirectional) I2C multiplexer which allows eight separate I2C devices to be controlled by a single host I2C bus. You just need to wire up the I2C sensors to the SC / SD multiplexed buses. consider the PCA9548A itself. It is the gateway between your Arduino and eight separate I2C buses. You have a single bus on one side, connected to your Arduino.
On the other side of the PCA9548A, you have eight I2C buses, and only one of these can be connected to the Arduino at a time.
Interface: I2C IIC
Selectable I2C address: 0x70-0x77
Working Voltage: 1.65-5.5V
Max Clock Frequency: 400 kHz
Pinout of the PCA9548 Expansion Board 8ch 1 to 8 I2C Multiplexer
- Vin - this is the power pin. Since the sensor chip uses 3-5 VDC. To power, the board, give it the same power as the logic level of your microcontroller - e.g. for a 5V micro like Arduino, use 5V
- GND - common ground for power and logic
- SCL - this is the I2C clock pin for the chip itself, connect to your microcontroller I2C clock line.
- SDA - this is the I2C data pin for the chip itself, connect to your microcontroller I2C data line.
- RST - this is the reset pin, for resetting the multiplexer chip. Pulled high by default, connect to ground to reset
- A0 A1 A2 - these are the address selection pins for the multiplexer. By default, the multiplexer is at address 0x70 and these three pins are pulled low. Connect them to Vin to set the address to 0x71 - 0x77.
- A0 is the lowest-significant bit (if it is pulled high, it will increase the address by 1).
- A1 is the 2nd-lowest-significant bit (if it is pulled high, it will increase the address by 2).
- A2 is the 3rd-lowest-significant bit (if it is pulled high, it will increase the address by 4).
- SDx and SCx: There are 8 sets of SDx and SCx pins, from SD0/SC0 to SD7/SC7. These are the multiplexed pins. Each one is a completely separate I2C bus set. So you have 8 I2C devices with identical addresses, as long as they are on one I2C bus each.
- These pins do not have any pull-ups installed, so if you are using a chip or breakout without i2c pullups be sure to add them! Nicely, you can have Vin be 3.3V and have these pins pulled up to 5V (that is, they are 5V compliant)
VIN to 5V (or 3.3V)
GND to ground
SDA to A4 and
SCL to A5 pins respectively
Once the MUX is hooked up to the micro-controller, you just need to connect the sensors to the SCn / SDn pairs.