ESP8266: Externalizing multiplexer logic produces errors - c++

Question

I have an I2C multiplexer connected to my ESP8266 and attached five SH1106 OLED displays to it (bus 2 to 6). I tested everything with simple example code and it works. I have then written the following code in which I try to externalize the display switch logic to an own class and make it more handy to use. It compiles and loads onto the board, but I keep getting errors and only one of the display infrequently flickers the word "TEST". Do you have any idea why?
main.cpp :
#include <Arduino.h>
#include <services/displayservice/DisplayService_h>
#include "SH1106Wire.h"
DisplayService displayService;
void setup() {
}
void loop() {
for (int i = 2; i <= 6; i++) {
SH1106Wire display = displayService.display(i);
delay(2000);
display.clear();
display.flipScreenVertically();
display.setFont(ArialMT_Plain_24);
display.setTextAlignment(TEXT_ALIGN_CENTER);
display.drawString(64, 20, String("TEST"));
display.display();
delay(500);
}
}
With my own class DisplayService:
DisplayService_h :
#ifndef DisplayService_h
#define DisplayService_h
#include "SH1106Wire.h"
class DisplayService {
public:
DisplayService();
SH1106Wire display(u_int8_t displayNumber);
private:
void changeDisplay(u_int8_t displayNumber);
};
#endif
DisplayService.cpp :
#include "Arduino.h"
#include "SH1106Wire.h"
#include <Wire.h>
#include "DisplayService_h"
SH1106Wire displayObject(0x3C, SDA, SCL); // ADDRESS, SDA, SCL
DisplayService::DisplayService() {}
SH1106Wire DisplayService::display(u_int8_t displayNumber){
Serial.println(displayNumber);
this->changeDisplay(displayNumber);
displayObject.init();
return displayObject;
}
void DisplayService::changeDisplay(u_int8_t displayNumber){
Wire.beginTransmission(0x70); // TCA9548A address
Wire.write(1 << displayNumber); // send byte to select bus
Wire.endTransmission();
}
"Error message" if you can call it that :
ets Jan 8 2013,rst cause:2, boot mode:(3,7)
load 0x4010f000, len 3460, room 16
tail 4
chksum 0xcc
load 0x3fff20b8, len 40, room 4
tail 4
chksum 0xc9
csum 0xc9
v00046240
~ld

Answer 1

I don't know the reason, but I found a solution: Instead of passing the display object around, I now pass only a pointer to the display.
#include "Arduino.h"
#include "SH1106Wire.h"
#include <Wire.h>
#include "DisplayService_h"
SH1106Wire aDisplay(0x3C, SDA, SCL); // ADDRESS, SDA, SCL
DisplayService::DisplayService() {
}
SH1106Wire* DisplayService::display(u_int8_t displayNumber){
this->changeDisplay(displayNumber);
aDisplay.init();
return &aDisplay;
}
void DisplayService::changeDisplay(u_int8_t displayNumber){
Wire.beginTransmission(0x70); // TCA9548A address
Wire.write(1 << displayNumber); // send byte to select bus
Wire.endTransmission();
}
However, it wouldn't work if I wouldn't init the display each time I change the active display.