problem with charaters >127

[Karl-250]

Hello everyone,
While getting familiar with the u8g2 library, I am using a small monochrome OLED Display 0,91"with I2C Interface and the ESP32 chip with the ESP-IDF. The project I programmed was a progress bar with charaters that are inverted when the progress bar overlay them. I used the DrawColor Option 2 -> XOR and the font in transparent mode. Everything worked graet !! until the moment I added "°C" to the string. ° and C are flickering. Using a character <=127 in the font list (u8g2_font_helvB24_tf) there is no problem. Using characters >127 the flickering occurs. For displaing characters > 127 I use „u8g2_DrawUTF8“.
Interesting is, when I change the sequence from „°C“ to „C°“, the „C“ is displayed correctly and "°" flickers. Is that a known bug ? Does there exists a workaround ?

Best regards Karl

[olikraus]

Difficult to tell without the code, but maybe https://github.com/olikraus/u8g2/wiki/u8g2reference#enableutf8print helps

[Karl-250]

Hi Oli,

Here the relevant code snippet:

void ProgressBar(int wert, int last_wert)
{
u8g2_SetFontMode(&u8g2,1);//transparent mode

if(wert<10) //right adjust digits
	{
		OffsetDigit = 18*2;
	}
	else if(wert>=10 && wert<100)
	{
		OffsetDigit = 18;
	}
	else
	{
		OffsetDigit = 0;
	}

	//assemble string to be displayed
	sprintf(value_as_c, "%d",wert);//convert numerical value to string
	strcat(value_as_c, "°C");// add to string at the end

	printf("%s\n",value_as_c);//print to monitor

	//clear old characters and box
	u8g2_SetDrawColor(&u8g2,0);
	u8g2_DrawStr(&u8g2,(Position+Last_OffsetDigit),28,last_value_as_c);
	u8g2_DrawBox(&u8g2,3,3,last_wert,26);

	//draw actual BOX
	u8g2_SetDrawColor(&u8g2,1);	 		
	u8g2_DrawBox(&u8g2,3,3,wert,26);

	//draw actual string
	u8g2_SetDrawColor(&u8g2,2);//Mode XOR
	u8g2_DrawUTF8(&u8g2,(Position+OffsetDigit),28,value_as_c);

	u8g2_SendBuffer(&u8g2);

	Last_OffsetDigit = OffsetDigit;								
	strcpy(last_value_as_c,value_as_c);		

}

When I change the sequence of " °C° to " C°", the C is displayed correctly.
The command "enableutf8print" only exists with Arduino, I am using the ESP-IDF.

best regards Karl

[Karl-250]

Hi,
I found the solution:
For drawing I used "DrawUTF8" for clearing the "DrawString" command. For clearing its also neccessary to use the DrawUTF8 command .
best regards Karl

[olikraus]

Yes... correct.