U8X8_SSD1305_128X32_NONAME_2ND_HW_I2C isn’t a constructor?

[FGasper]

Hello,

Maybe I’m misunderstanding something in the documentation, but when I replace:

U8X8_SSD1306_128X64_NONAME_4W_SW_SPI u8x8(/* clock=*/ 13, /* data=*/ 11, /* cs=*/ 10, /* dc=*/ 9, /* reset=*/ 8);

… with:

U8X8_SSD1305_128X32_NONAME_2ND_HW_I2C u8x8();

… and try to verify the code, Arduino IDE gives me:

request for member 'begin' in 'u8x8', which is of non-class type 'U8X8_SSD1305_128X32_NONAME_2ND_HW_I2C()'

Here’s my full sketch; is there something I’m missing?

#include <Arduino.h>
#include <SPI.h>
#include <U8x8lib.h>

/* Constructor */
//U8X8_SSD1306_128X64_NONAME_4W_SW_SPI u8x8(/* clock=*/ 13, /* data=*/ 11, /* cs=*/ 10, /* dc=*/ 9, /* reset=*/ 8);
U8X8_SSD1305_128X32_NONAME_2ND_HW_I2C u8x8(void);

/* u8x8.begin() is required and will sent the setup/init sequence to the display */
void setup(void)
{
  u8x8.begin();
}

void loop(void)
{
  u8x8.setFont(u8x8_font_chroma48medium8_r);
  u8x8.drawString(0,0,"Hello World!");
  delay(1000);
}

Thank you!

[FGasper]

It appears that specifying the reset pin is needed. I’m going to leave this issue open in case an update to the docs seems warranted.

Thank you!

[olikraus]

Hmm.. you skip the reset pin from my perspective, the problem seems to be the "void" argument, which is probably not valid: U8X8_SSD1305_128X32_NONAME_2ND_HW_I2C u8x8(void); This should be U8X8_SSD1305_128X32_NONAME_2ND_HW_I2C u8x8(); instead.

Actually this is not a u8g2 issue more a general C++ topic.

[hansmbakker]

I see this is closed, but I do have the same error when doing

U8X8_SSD1306_128X32_UNIVISION_HW_I2C u8x8();

(without literally specifying void as a parameter). Is this expected behavior?

[olikraus]

Which error exactly you have?

[hansmbakker]

The relevant parts of my code are:

#include <U8x8lib.h>
U8X8_SSD1306_128X32_UNIVISION_HW_I2C display();

void printOnDisplay(std::string text, bool keepOnDisplay)
{
  display.drawString(0, 0, text.c_str());
  if (!keepOnDisplay)
  {
    delay(1000);
    display.clearDisplay();
  }
}

void setup()
{
  display.begin();
  printOnDisplay(std::string("Hello"), true);
  delay(3000);
  display.clearDisplay();
}

void loop()
{
}

The relevant errors I get are:

[olikraus]

Hm strange. Maybe try:

U8X8_SSD1306_128X32_UNIVISION_HW_I2C display(U8X8_PIN_NONE);

[hansmbakker]

Sorry for my late response!

U8X8_SSD1306_128X32_UNIVISION_HW_I2C display(U8X8_PIN_NONE);

works!

Which is odd though, because the constructor does have a default parameter value: https://github.com/olikraus/u8g2/blob/a543c481319f381e91c0caea664b7be5ade59635/cppsrc/U8x8lib.h#L2143

I don't have the C++ experience to understand why this still happens, so unfortunately I cannot create a PR for this.

Would it be possible to update the docs at https://github.com/olikraus/u8g2/wiki/u8x8setupcpp#ssd1306-128x32_univision-1? There the parameter is marked optional.

[olikraus]

I agree, your constructor should also work. Maybe Arduino IDE changes something here. It runs a preprocessor on the code. :-/