After long time writing Smbus to work with SSD1306 oled and displaying a splash from predefined array, its time for Text and etc.
I read all over internet and I see code like WriteLcd() function and similar.
Im using EFM8 mcu and pretty much will need to write draw function from scratch. What's the process to draw text and numbers.
Trying to display data from I2C current sensor into oled.

 

In a graphic display the display characters are "normally" stored in n x n bit mapped
font in memory. So take for example a 5 x 7

This is bit packed into memory different ways, but with a logical
ordering, such that you can retrieve row by row or col by col
the data to output to display. Usually done in C by using pointers.

That's oversimplification, but is really a very basic operation of
reading the characters data by row or col and, then outputing that
to either a display buffer or display memory.

Of course on display side you keep track of where you are writing
in its memory. Usually a good practice is to clear the region you are
going to use, then doing the writes.

I have found to get flicker free displays a duplicate buffer to display
is kept. When time to update the buffer is checked, if the region of
interest in buffer has to change, then buffer and display updated for
that region. If no change nothing is done. This cuts down dramatically
the write activity to display which can cause display "artifacts" to occur
due to the non synchronous nature of most displays. That is write a
character already in display, over and over, but display internal controller
not synched to write activity so human eye will pick up display being
updated constantly rather than as needed.

Regards, Dana.

 

Hi Dana,

I guess Im not sure how to point to corresponding letter. Lets say I have a string TEST.
I count how much space I need and clear the space. But then how it knows T is T font?

 

It all depends on the display and display controller you have.
Some you position the cursor and then write ascii value of
char to the display for that position and the controller takes
over and pulls from its internal memory the bitmap and updates
its internal display buffer. Others you link in a font library for
storage in UP FLASH, then you do the retrieves of the char
array and pull out row by row and send to the display buffer.

Regards, Dana.