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MicroPython TCA9548A 8-Channel I2C Multiplexer

A MicroPython library for the CJMCU-9548 module, featuring the TCA9548A. This module lets you run multiple I2C devices with the same address on the bus, by spreading the conflicting devices across 8 channels and toggling between them.

The module itself is present on the I2C bus with a configurable address of 0x70-0x77 using the A0,A1,A2 pins. This lets you daisy chain them and have up to 64 devices on the bus with the same address.

It features a single 8-bit register, where each bit enables each of the 8 channels. I2C channel 0 is enabled with the LSB and channel 7 with the MSB. You can also enable multiple channels at the same time.

demo

Examples

from machine import I2C, Pin
i2c = I2C(scl=Pin(22), sda=Pin(21))

# disable all 8 channels
i2c.writeto(0x70, b'\x00')
i2c.scan()
# [112] - the TCA9548A

# enable channel 0 (SD0,SC0)
i2c.writeto(0x70, b'\x01')
i2c.scan()
# [60, 112] - Display 1 (SSD1306) & TCA9548A

# enable channel 1 (SD1,SC1)
i2c.writeto(0x70, b'\x02')
i2c.scan()
# [60, 112] - Display 2 (SSD1306) & TCA9548A

# enable channels 0 (SD0,SC0) & 2 (SD2,SC2)
i2c.writeto(0x70, b'\x05')
i2c.scan()
# [60, 68, 112] - Display 1 (SSD1306) & SHT31 sensor & TCA9548A

# read which channels are enabled?
i2c.readfrom(0x70, 1)
# b'\x05' - channels 0 and 2 (0x05 == 0b_0000_0101)

# enable all 8 channels
i2c.writeto(0x70, b'\xff')

# disable all 8 channels
i2c.writeto(0x70, b'\x00')

demo

Two SSD1306 OLED displays

from machine import I2C, Pin
i2c = I2C(scl=Pin(22), sda=Pin(21))
i2c.scan()
# [112]

# enable channel 0 (SD0,SC0)
i2c.writeto(0x70, b'\x01')
i2c.scan()
# [60, 112]

import ssd1306
oled = ssd1306.SSD1306_I2C(128, 64, i2c)

# write to the first display
oled.fill(0)
oled.text('Display 1', 0, 0, 1)
oled.show()

# enable channel 1 (SD1,SC1)
i2c.writeto(0x70, b'\x02')

# init the second display
oled.init_display()

# write to the second display
oled.fill(0)
oled.text('Display 2', 0, 0, 1)
oled.show()

# enable channels 0 (SD0,SC0) & 1 (SD1,SC1)
i2c.writeto(0x70, b'\x03')

# write to the both displays
oled.fill(0)
oled.text('Hello', 0, 0, 1)
oled.show()

I2C Address

There are three address select pins (A0,A1,A2) providing addresses 0x70-0x77 for up to 8 of these devices on the I2C bus.

The CJMCU-9548 module has pull-downs on the 3x address select pins, so you only need to connect them to VCC to change the address.

A0	A1	A2	I2C Address
GND	GND	GND	0x70
3V3	GND	GND	0x71
GND	3V3	GND	0x72
3V3	3V3	GND	0x73
GND	GND	3V3	0x74
3V3	GND	3V3	0x75
GND	3V3	3V3	0x76
3V3	3V3	3V3	0x77

Parts

TinyPICO $20.00 USD
TCA9548A CJMCU-9548 $1.23 AUD

Connections

TinyPICO ESP32

from machine import Pin, I2C
i2c = I2C(scl=Pin(22), sda=Pin(21))

TCA9548A	TinyPICO (ESP32)
VIN	3V3
GND	GND
SCL	22 (SCL)
SDA	21 (SDA)

License

Licensed under the MIT License.