\/\/ Select I2C BUS\nvoid TCA9548A(uint8_t bus){\n Wire.beginTransmission(0x70); \/\/ TCA9548A address\n Wire.write(1 << bus); \/\/ send byte to select bus\n Wire.endTransmission();\n Serial.print(bus);\n}<\/code><\/pre>\n\n\n\nYou must call this function whenever you want to select the I2C port.<\/p>\n\n\n\n
setup()<\/h4>\n\n\n\n In the setup()<\/span>, initialize a serial communication for debugging purposes.<\/p>\n\n\n\nSerial.begin(115200);<\/code><\/pre>\n\n\n\nStart I2C communication on the default I2C pins with the I2C multiplexer.<\/p>\n\n\n\n
Wire.begin();<\/code><\/pre>\n\n\n\nThen, initialize each display. The following lines show an example for the first OLED display (it is connected to bus number 2).<\/p>\n\n\n\n
\/\/Init OLED display on bus number 2\nTCA9548A(2);\nif(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {\n Serial.println(F(\"SSD1306 allocation failed\"));\n for(;;);\n} \n\/\/ Clear the buffer\ndisplay.clearDisplay();<\/code><\/pre>\n\n\n\nInitializing the other displays is similar, but you need to call the TCA9548A()<\/span> function with the corresponding I2C bus number.<\/p>\n\n\n\nThen, write something to the displays. Don’t forget you need to call the TCA9548A()<\/span> function every time you want to switch between OLEDs. You also need to clear the display buffer before writing anything to the OLED.<\/p>\n\n\n\n\/\/ Write to OLED on bus number 2\nTCA9548A(2);\ndisplay.clearDisplay();\ndisplay.setTextSize(8);\ndisplay.setTextColor(WHITE);\ndisplay.setCursor(45, 10);\n\/\/ Display static text\ndisplay.println(\"1\");\ndisplay.display(); <\/code><\/pre>\n\n\n\nIn this case, we’re just printing a different number on each display. Here’s an example for OLED number 4 (it is connected to bus number 5).<\/p>\n\n\n\n
\/\/ Write to OLED on bus number 5\nTCA9548A(5);\ndisplay.clearDisplay();\ndisplay.setTextSize(8);\ndisplay.setTextColor(WHITE);\ndisplay.setCursor(45, 10);\n\/\/ Display static text\ndisplay.println(\"4\");\ndisplay.display();<\/code><\/pre>\n\n\n\nAnd that’s pretty much how the code works.<\/p>\n\n\n\n
The following code shows a similar example but using multiple Adafruit_SSD1306<\/span> instances. Notice that you don’t need to clear the buffer before writing to the display.<\/p>\n\n\n\/*********\r\n Rui Santos\r\n Complete project details at https:\/\/RandomNerdTutorials.com\/tca9548a-i2c-multiplexer-esp32-esp8266-arduino\/\r\n \r\n Permission is hereby granted, free of charge, to any person obtaining a copy\r\n of this software and associated documentation files.\r\n \r\n The above copyright notice and this permission notice shall be included in all\r\n copies or substantial portions of the Software.\r\n*********\/\r\n\r\n#include <Wire.h>\r\n#include <Adafruit_GFX.h>\r\n#include <Adafruit_SSD1306.h>\r\n\r\n#define SCREEN_WIDTH 128\r\n#define SCREEN_HEIGHT 64\r\n\r\nAdafruit_SSD1306 display1(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);\r\nAdafruit_SSD1306 display2(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);\r\nAdafruit_SSD1306 display3(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);\r\nAdafruit_SSD1306 display4(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);\r\n\r\n\/\/ Select I2C BUS\r\nvoid TCA9548A(uint8_t bus){\r\n Wire.beginTransmission(0x70); \/\/ TCA9548A address\r\n Wire.write(1 << bus); \/\/ send byte to select bus\r\n Wire.endTransmission();\r\n Serial.print(bus);\r\n}\r\n\r\nvoid setup() {\r\n Serial.begin(115200);\r\n\r\n \/\/ Start I2C communication with the Multiplexer\r\n Wire.begin();\r\n\r\n \/\/ Init OLED display on bus number 2 (display 1)\r\n TCA9548A(2);\r\n if(!display1.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {\r\n Serial.println(F("SSD1306 allocation failed"));\r\n for(;;);\r\n } \r\n \/\/ Clear the buffer\r\n display1.clearDisplay();\r\n\r\n \/\/ Init OLED display on bus number 3\r\n TCA9548A(3);\r\n if(!display2.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {\r\n Serial.println(F("SSD1306 allocation failed"));\r\n for(;;);\r\n } \r\n \/\/ Clear the buffer\r\n display2.clearDisplay();\r\n\r\n \/\/ Init OLED display on bus number 4\r\n TCA9548A(4);\r\n if(!display3.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {\r\n Serial.println(F("SSD1306 allocation failed"));\r\n for(;;);\r\n } \r\n \/\/ Clear the buffer\r\n display3.clearDisplay();\r\n\r\n \/\/ Init OLED display on bus number 5\r\n TCA9548A(5);\r\n if(!display4.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {\r\n Serial.println(F("SSD1306 allocation failed"));\r\n for(;;);\r\n } \r\n \/\/ Clear the buffer\r\n display4.clearDisplay();\r\n\r\n \/\/ Write to OLED on bus number 2\r\n TCA9548A(2);\r\n display1.setTextSize(8);\r\n display1.setTextColor(WHITE);\r\n display1.setCursor(45, 10);\r\n \/\/ Display static text\r\n display1.println("1");\r\n display1.display(); \r\n \r\n \/\/ Write to OLED on bus number 3\r\n TCA9548A(3);\r\n display2.setTextSize(8);\r\n display2.setTextColor(WHITE);\r\n display2.setCursor(45, 10);\r\n \/\/ Display static text\r\n display2.println("2");\r\n display2.display(); \r\n \r\n \/\/ Write to OLED on bus number 4\r\n TCA9548A(4);\r\n display3.setTextSize(8);\r\n display3.setTextColor(WHITE);\r\n display3.setCursor(45, 10);\r\n \/\/ Display static text\r\n display3.println("3");\r\n display3.display(); \r\n \r\n \/\/ Write to OLED on bus number 5\r\n TCA9548A(5);\r\n display4.setTextSize(8);\r\n display4.setTextColor(WHITE);\r\n display4.setCursor(45, 10);\r\n \/\/ Display static text\r\n display4.println("4");\r\n display4.display();\r\n}\r\n \r\nvoid loop() {\r\n \r\n}\r\n<\/code><\/pre>\n\tView raw code<\/a><\/p>\n\n\n\nDemonstration<\/h3>\n\n\n\n Upload the code to your board. Here’s what you should get.<\/p>\n\n\n\n
As you can see, it is pretty easy to control multiple OLED displays showing different graphics using an I2C multiplexer.<\/p>\n\n\n\n
Read Multiple BME280 Sensors \u2014TCA9548A I2C Multiplexer<\/h2>\n\n\n\n In this section, you’ll learn how to read data from multiple BME280 sensors using the TCA9548A I2C multiplexer. We’ll read data from four sensors, but you can hook up to 8 sensors.<\/p>\n\n\n\n
Parts Required<\/h4>\n\n\n\n Here’s a list of the parts required for this example:<\/p>\n\n\n\n
![\"Guide](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2021\/07\/Guide-TCA9548A-I2C-Multiplexer-ESP32-EP8266-Arduino.jpg?resize=1200%2C675&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n\n![\"TCA9548A](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2021\/07\/TCA9548A-I2C-Multiplexer-Sensor-Module.jpg?resize=750%2C419&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n\n![\"TCA9548A](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2021\/07\/TCA9548A-How-it-Works.png?resize=739%2C363&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n\n![](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2017\/10\/header-200.png?w=1200&quality=100&strip=all&ssl=1\")
<\/a><\/p>\n\n\n\n![\"Multiple](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2021\/07\/multiple-OLED-displays-TCA9548A-I2C-Multiplexer.jpg?resize=1200%2C1052&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n\n![\"OLED](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2021\/07\/OLED-Demonstration-TCA9548A-I2C-Multiplexer-Sensor-Module.jpg?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n\n![\"BME280](\"https:\/\/i0.wp.com\/randomnerdtutorials.com\/wp-content\/uploads\/2021\/07\/BME280-Demonstration-TCA9548A-I2C-Multiplexer-Sensor-Module.jpg?resize=750%2C422&quality=100&strip=all&ssl=1\")
<\/figure><\/div>\n\n\n\n