70x42 OLED ? about ssd1306ascii

[greiman]

I look at u8g2 for hints when there are problems with a display.

I looked at u8x8_d_ssd1306_72x40.c.

The one thing I noticed for the 72x40 display was a default_x_offset of 28. This is at about line 240.

This probably is not the problem since you are using zero for column offset and only have a column of bad pixels.

You could try an offset of two since SH1106 controllers often require an offset of two. There is a file u8x8_d_sh1106_72x40.c but it has an offset of 30.

May be you can see something else in these files.

Sorry I have no other ideas what is causing your problem.

[urish]

Update: the simulator issue was fixed!

Thanks @greiman for pointing out the SSD1306_SETSTARTLINE command, the issue was indeed there.

[Sarah-C]

Thanks for checking! I'll have a go after work.

[Sarah-C]

@greiman hi!

Could you spare a moment to look at this sketch in the emulator?

Just press the green play button, and it fills the OLED with "123"'s.

When it gets to the bottom, is the screen behaving how you coded it? I thought it would scroll the text up a line, in which case I'll raise a bug with wokwi. If it behaves as it should, my Universal Terminal object will come into its own! =)

https://wokwi.com/projects/338268461896565332

[greiman]

The emulator does not behave correctly. I write data in to the controller RAM as a circular buffer and map the display start line with a command.

I suspect that the emulator does not correctly implement this command:

/** Set display RAM display start line register from 0 - 63. */
#define SSD1306_SETSTARTLINE 0x40

It is used in this functions to map the RAM to the display:

void SSD1306Ascii::setStartLine(uint8_t line) {
  m_startLine = line & 0X3F;
  ssd1306WriteCmd(SSD1306_SETSTARTLINE | m_startLine);
}

[Sarah-C]

I'll let the authors know. Thank you!

[Sarah-C]

As it's unrelated to this library, I'm closing the issue. Thank you all.

[urish]

@Sarah-C thanks for reporting! I ran your code against physical hardware, and can see it indeed behaves differently:

ssd1306-issue.mp4

I opened an issue to track the bug on wokwi/wokwi-features#394