This article is about connecting the ESP8266 to an OLED, which is a two-color graphic LED, where 0 represents blank and 1 represents color dot. It is connected to the microcontroller via the I2C bus. How to use it and its functions are discussed as a guide and reference material for further implementation.
Display controller
There are two types of LED display controllers: sh1106 or ssd1306 ICs. The LED modules are not usually specified, so the user can’t see because it is obscured by the LED module. The OLED (available in blue and white, or some models are assigned some rows to one color and some rows to another) selected in this article is I2C as shown in picture 2 and connected to esp8266 as shown in picture 3.
Required library
import sh1106
or
import ssd1306
To run it, you have to see what the results are. If it comes out wrong, go back and choose another one.
Prepare i2c
from machine import I2C, Pin
i2c = I2C(sda=Pin(4), scl=Pin(5))
oled_addr = const(0x3c)
oled = sh1106.SH1106_I2C(128,64,i2c,None,oled_addr)After running the library for the LED controller, the next step is to enable the I2C bus and create a variable to point to the OLED module.
Show message
oled.text("text", x, y, c=1)where
c is the color dot, where 1 represents light and 0 represents black.
x,y are the coordinates of the upper-left corner of the initialized text.
Display information on the display
oled.show()The show( ) command instructs the LED module controller to write data from all buffers to the LED module. Enable the visibility of the results of the commands assigned to the control.
Fill color
oled.fill( 1 ) # เติมสีสว่าง
oled.fill( 0 ) # เติมสีดำColor Fill sets the background color of all LED modules to a color 0 or 1 like clearing the screen with a color 0 or 1.
Place the pixels at the position (x,y).
oled.pixel( x, y, c )where
x,y is the pixel coordinate where x values are in the range [0, 127] and y are in the range [0, 63]. c is the color value of the pixel which has a value of 0 or 1.
Invert the color
oled.invert( True )
oled.invert( False )Inverting the color causes the dot to be changed to the opposite color, i.e. 0 is changed to 1, and from 1 it becomes 0. Therefore, when a color inversion technique is applied to screen flickers 5 times in 1 second, code is written as follows
for counter in range(5):
oled.invert(True)
time.sleep_ms(100)
old.invert(False)
time.sleep_ms(100)Read the color value at the position (x,y)
c = oled.pixel( x, y )where c is the color value read from the coordinates (x,y).
Draw a straight line horizontally.
oled.hline( x, y, w, c=1 )where
x,y is the starting position
w is the length of the line c is the color
Draw a straight line vertically.
oled.vline( x, y, h, c=1 )where
x,y is the starting position h is the length of
the line c is the color
draw a straight line
oled.line( x1, y1, x2, y2, c=1 )where
x1,y1 are the initial coordinates of the line.
x2,y2 are the ending coordinates of the line. c is the color
Draw a square
oled.rect( x, y, w, h, c )where
x,y are the coordinates of the upper left corner of the rectangle.
w is the width of the rectangle
h is the height of the square c is the color
Draw a solid square
oled.fill_rect( x, y, w, h, c )where
x,y are the coordinates of the upper left corner of the rectangle.
w is the width of the rectangle
h is the height of the square c is the color
Scroll the screen in the x and y axes.
oled.scroll( x, y )where
x is the shift position in the x-axis.
y is the scroll position in the y-axis. For example, want to scroll down the screen 4 points and move to the left 8 points can be ordered as
oled.scroll( -8, -4 )Drawing created by pixel art.
Drawing using one data per pixel.
Step 1: Create an image variable, e.g. to display “ก”.
korkai = [
[ 0, 0, 1, 1, 1, 1, 1, 0 ],
[ 0, 1, 0, 0, 0, 0, 0, 1 ],
[ 0, 0, 1, 0, 0, 0, 0, 1 ],
[ 0, 1, 0, 0, 0, 0, 0, 1 ],
[ 0, 1, 0, 0, 0, 0, 0, 1 ],
[ 0, 1, 0, 0, 0, 0, 0, 1 ],
[ 0, 1, 0, 0, 0, 0, 0, 1 ],
[ 0, 1, 0, 0, 0, 0, 0, 1 ]
]Step 2 pixel e.g.
for ch_row in range(8):
for ch_col in range(8):
oled.pixel( ch_col, ch_row, korkai[ch_row][ch_col] )Step 3 display
oled.show( )Drawing using 1 bit of data per pixel.
Step 1: Create an image variable, e.g. to display “ก”.
korkai = [
0b00111110,
0b01000001,
0b00100001,
0b01000001,
0b01000001,
0b01000001,
0b01000001,
0b01000001
]Step 2 pixel e.g.
for ch_row in range(8):
bit = 0x80
for ch_col in range(8):
cl = korkai[ch_row]&bit
oled.pixel( ch_col, ch_row, cl)
bit >>= 1Step 3 Display
oled.show( )Drawing in bits and making it bold.
Modify Step 2 to draw two adjacent pixels instead of just one.
for ch_row in range(8):
bit = 0x80
for ch_col in range(8):
cl = korkai[ch_row]&bit
oled.pixel( ch_col*2, ch_row, cl)
oled.pixel( ch_col*2+1, ch_row, cl)
bit >>= 1Drawing in bits and giving it 2 times the size.
Modify Step 2 to draw a 2×2 filled square instead of pixels.
for ch_row in range(8):
bit = 0x80
for ch_col in range(8):
cl = korkai[ch_row]&bit
oled.fill_rect( ch_col*2, ch_row*2, 2, 2, cl)
bit >>= 1Transparent drawing
Drawing transparent or translucent is to check the color data in the drawing, that is, if it is 1, it will plot the color, but if it is 0, it will not plot the color. It will not overlaid with 0 colors. For example, the transparent check and drawing is as follows.
for ch_row in range(8):
bit = 0x80
for ch_col in range(8):
cl = korkai[ch_row]&bit
if cl:
oled.pixel( ch_col, ch_row, 1)
bit >>= 1Store the bitmap as a bytearray.
Step 1: Create an image variable, for example, want to represent “ก”, this method guarantees the size of each dataset is 1 byte.
korkai = bytearray(
[0b00111110,
0b01000001,
0b00100001,
0b01000001,
0b01000001,
0b01000001,
0b01000001,
0b01000001]
)Step 2 pixel e.g.
for ch_row in range(8):
bit = 0x80
for ch_col in range(8):
cl = korkai[ch_row]&bit
oled.pixel( ch_col, ch_row, cl)
bit >>= 1Step 3 Display
oled.show( )Adjust brightness
oled.contrast( cn )where cn is the brightness level in the range 0 to 255.
Blit
Blit is a technique of sending a WxH size buffer to the display buffer. Results in better transmission efficiency than displaying WxH pixels by looping W*H times.
The data format applied to the blitz must be a bytearray and the format of the command is as follows.
oled.blit( buf, x, y )โดย
where
buf is a FrameBuffer data type that stores image data. x,y are the coordinates of the top-left corner of the LED module used to initialize the image.
The process of creating a framebuffer data is as follows:
import framebuf
data = bytearray([data])
buf = framebuf.FrameBuffer( data, width, height, framebuf.MONO_HLSB)Example of drawing “ก” with a blit
Step 1: Create an image variable, e.g. to display “ก”.
korkai = bytearray(
[0b00111110,
0b01000001,
0b00100001,
0b01000001,
0b01000001,
0b01000001,
0b01000001,
0b01000001]
)Step 2 create FrameBuffer
buf = framebuf.FrameBuffer( korkai, 8, 8, framebuf.MONO_HLSB)Step 3. Blot the image at the position (x, y).
oled.blit(buf, x, y )Step 4 Display
oled.show( )Conclusion
From this article, we can operate the OLED module display via the I2C bus using only 2 signal wires, sda and scl, and learn the commands and examples of how to use it. Finally, we hope this article will be helpful to you and have fun with programming.
If you want to discuss or share with us, please leave comments below!
References
(C) 2020-2021, By Jarut Busarathid and Danai Jedsadathitikul
Updated 2021-10-05