U8G2 OLED Multiplexing issue

Projects Programming
1

Sorry, I am here seeking for help of my OLED multiplexing issue. I tried to use this TCA9548A (from DFRobot) to multiplex two u8g2 supported OLEDs but failed (nothing showed). However, I tested each OLED successfully (by connecting it to ESP32 i2c bus). So things must go to the multiplexing problem, may I know what's happening? Thanks a lot.

#include <Arduino.h>
#include <U8g2lib.h>
#include <Wire.h>
//#include <DFRobot_I2C_Multiplexer.h>

#define TCA9548A 0x70
void tselect(uint8_t i) {
  if (i > 7) return;
  Wire.beginTransmission(TCA9548A);
  Wire.write(1 << i);
  Wire.endTransmission();
}

U8G2_SSD1306_128X64_NONAME_F_HW_I2C u8g2(/* rotation=*/U8G2_R0, /* reset=*/U8X8_PIN_NONE);

//Create an I2C Multiplexer object, the address of I2C Multiplexer is 0X70*/
//DFRobot_I2C_Multiplexer I2CMulti(&Wire, 0x70);

void setup(void) {
  Serial.begin(115200);
  for (int i = 0; i <= 7; i++) {
    tselect(i);
    u8g2.setI2CAddress(0x3C);
    u8g2.begin();
    Wire.begin();
  }
  tselect(0);
  //u8g2.begin();
  u8g2.clearBuffer();                   // clear the internal memory
  u8g2.setFont(u8g2_font_t0_17b_tr);    // choose a suitable font
  u8g2.drawStr(0, 10, "Hello World!");  // write something to the internal memory
  u8g2.sendBuffer();                    // transfer internal memory to the display
  delay(1000);
}
2

Nothing is reported from the Arduino "Output" Section.

3

The code you posted won't compile, you can't upload it to the Arduino. The loop() function is missing.

4

Perhaps your loop() function is empty?

Try this:

void setup(void) {
  Serial.begin(115200);
  Wire.begin();
  u8g2.setI2CAddress(0x3C);
  u8g2.begin();
  for (int i = 0; i <= 7; i++) {
    tselect(i);
    u8g2.clearBuffer();                   // clear the internal memory
    u8g2.setFont(u8g2_font_t0_17b_tr);    // choose a suitable font
    u8g2.drawStr(0, 10, "Hello World!");  // write something to the internal memory
    u8g2.sendBuffer();                    // transfer internal memory to the display
    delay(1000);
  }
}
5

Thanks for your answer. I included loop() function actually and modify the codes with your suggestions however things still are not working. Anyway, I will continue looking for the solutions.

6 
U8G2_SSD1306_128X64_NONAME_F_HW_I2C u8g2(/*rotation=*/U8G2_R0, /*reset=*/U8X8_PIN_NONE, 22, 21);

I think I got the solution. I shall add SCL and SDA pin config in the u8g2 object constructor for ESP32.