Tutorial-1: OLED Basic Programming

Introduction:

         In this tutorial series, we are going to see how to program an OLED display using any uController. I am saying 'any uController' because I am going to explain programming irrespective of uController used. 

            For simplicity, I am going to use Arduino Board for programming but the flow of programming and algorithm will be the same for other controllers like STM32, TivaC, ESP8266, ESP32 and any other uController with I2C bus compatibility.

Tutorials in this tutorial series Are as follows:

Tutorial Name	What we learn?
1) OLED Basic Programming	i)  Basic of OLED   ii) Power consumption  iii) Pixel arrangement  iv) Addressing modes of OLED  v) I2C Registers and Commands  vi) Writing First Program Sample Program:   Drawing chess Board layout
2) Using GLCD Font Creator      For designing patterns on      OLED	i)  What is GLCD Font Creator?   ii) Create HEX code for a chess Board layout in GLCD Sample Program:    i) Drawing chess Board layout designed in GLCD on 8x8 matrix    ii) Drawing chess Board layout designed in GLCD on 16x16 matrix
3) Adding custom font on      OLED	Create Hex code for a font in GLCD Sample Program:     i) Displaying custom font on OLED   created in GLCD
4) Adding Indian languages	Create Hex code for Devanagari Font Sample Program:          Displaying Devanagari font on OLED
5) Interfacing OLED display to      FPGA	Design a OLED driver for a low memory  microcontroller. Sample Program:          Displaying English and Devanagari  font on OLED

 This is the first tutorial and as mentioned in the above table we are going to see
                   i) Basics of OLED
                  ii) Power consumption 
                 iii) Pixel arrangement
                 iv) Addressing modes of OLED

         

                 We are not going to use any ready-made library (except library require for I2C communication which is provided by almost all controllers) so before programming, we should know some basic knowledge about OLED

  please watch the following video:

i) Basics of OLED 

                      In OLED displays, OLED(Organic Light Emitting Diode) is used. The main feature of OLED display is that it does not require a backlight. Hence we get good contrast in the OLED display.Also, it consumes less power. So this display is used in LOW POWER applications
                    In this tutorial series, we are going to use 0.96 inches 128x64 OLED display with SS1306 driver IC. 128x64 means it has 128 columns and 64 rows for pixels.

image1: 0.96 inches 128x64 OLED display

 ii) Power Consumption

                  As mentioned above, OLED is used for Low power applications. Using SS1306 IC which is diver IC of our OLED display we can adjust contrast/brightness in 256 levels(0 to 255 ).OLED consumes power only for the number of pixels which are lighted hence power consumption highly depends on how many pixels you are using to display your text and also on brightness level.


  Let us see some observations done by me about the power consumption of OLED display.


   Contrast = 255 (Full Brightness)

                       base current (all pixels OFF) = 350uA

                      

iii) Pixel Arrangement

                     OLED Display Driver has Graphics Display Data RAM(GDDRAM) whose size is 128x64 i.e each bit in this RAM corresponds to each pixel on the display. If any bit is 1 then pixel corresponding to that will be glowing.

image2: 128x64 Pixel arrangement

In the above image, we can see a 128x64 matrix of pixels. The whole matrix is vertically divided into 8 pages.

What is a page?
               A page is a row of a collection of 8 verticle pixel. one page contains a matrix of 128x8 pixels

image3: Single page view

       In the above image, we can see a single page view. All 8 pages are the same only there page no. is different that are 0 to 7.
               8-bit data in Display RAM is displayed on verticle eight pixels. Bottom Pixel corresponds to MSB of the data and top Pixel corresponds to LSB of the data.
There are two pointers in the RAM to point the position on the display:
  1) Column Address Pointer: (range: 0-127) pointer to 128 verticle columns
  2) Page Address Pointer : (Range:0-7) pointer to 8 pages

using these two pointers we can display our data on any page and any column.

iv) Addressing Modes of OLED

There are three addressing Modes in OLED
              1) Page Addressing Mode
              2) Horizontal Addressing mode
              3) Verticle Addressing Mode
                     
             We will concentrate on the first one, Page Addressing Mode only. 

      1) Page Addressing Mode    
                    
            

image4: Page Addressing Mode

             In the above image4, we can see how Page Addressing Mode work. In this addressing mode when we put data a column then column address pointer will increment by one.  When column address pointer reaches to its highest i.e 127 then it will be 0 again. page address pointer will remain the same.

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v) I2C Registers and Commands   

          Graphics Data RAM contains the data to be displayed. There are two registers, data register and Command register.
                
               Data Register: if we put data in this register, that data will be stored in RAM at the location pointed by Page Address Pointer and Column address pointer.  So if we to display an 8-bit data on a column of 8 pixels, we first need to set page address and column address then we need to put data in the data register and then corresponding 8-pixel column will display our 8-bit data. 
                 
               Command Register:  For operations like setting page no. , setting column no., turning display ON/OFF. For such operation, we need to put the corresponding command in this command register. You can refer to SSD1306 datasheet for these commands.


vi) Writing The First Program


         Following flowchart show the sequence of commands for initial setup of the OLED to turn it ON.
               

image5: OLED Turn On sequence

        Following flowchart showing the sequence of commands for setting X,Y cursor i.e to set column address pointer and Page Address pointer.

image6: Set X, Y cursor Sequence

    Circuit Diagram:

           Following is an Arduino Program in which we turn on display then clear full display by writing 0x00 on all column and pages then we are sending data 10101010 (0xAA in HEX) to light 4 pixels in the first column then column address pointer will be automatically incremented by 1 Hence if we send 01010101(0x55 in HEX) again then new data will be displayed in next column on the same page. In code we are sending above two byte data to display chessboard layout on OLED display in Page0.

The expected output of Arduino code on display:

image7: expected output on the display

Arduino Code: