Introduction of OLED Display
The new generation of small, interactive displays is a great way to add user-interactivity and interactivity with your favourite IoT project. The 0.96 inch OLED panel has been growing in popularity because it can be used as an input device or output screen for any application that requires these features such as
Health tracking systems where people wearables might monitor heart rates 24/7 without bothering you while sleeping at night!
Air quality monitoring system.
Tracking Bitcoin
Weather forecasting and many more.
One such oled display module is SSD1306.
Youtube link
Oled display Pins and Specifications
- 3V-5V Supply input Voltage
- 2ma -24ma current consumption
- 128 pixel wide and 64 pixel Tall
- Wide Viewing angle.
- Oled display will either use I2C or SPI. write about I2C or SPI accordingly.
Add image>>
Add a fritzing file link.
MicroPython based
Code:
Driver Code: || Src Code.
MicroPython Driver Code:
# MicroPython SSD1306 OLED driver, I2C and SPI interfaces
from micropython import const
import framebuf
# register definitions
SET_CONTRAST = const(0x81)
SET_ENTIRE_ON = const(0xA4)
SET_NORM_INV = const(0xA6)
SET_DISP = const(0xAE)
SET_MEM_ADDR = const(0x20)
SET_COL_ADDR = const(0x21)
SET_PAGE_ADDR = const(0x22)
SET_DISP_START_LINE = const(0x40)
SET_SEG_REMAP = const(0xA0)
SET_MUX_RATIO = const(0xA8)
SET_IREF_SELECT = const(0xAD)
SET_COM_OUT_DIR = const(0xC0)
SET_DISP_OFFSET = const(0xD3)
SET_COM_PIN_CFG = const(0xDA)
SET_DISP_CLK_DIV = const(0xD5)
SET_PRECHARGE = const(0xD9)
SET_VCOM_DESEL = const(0xDB)
SET_CHARGE_PUMP = const(0x8D)
# Subclassing FrameBuffer provides support for graphics primitives
# http://docs.micropython.org/en/latest/pyboard/library/framebuf.html
class SSD1306(framebuf.FrameBuffer):
def __init__(self, width, height, external_vcc):
self.width = width
self.height = height
self.external_vcc = external_vcc
self.pages = self.height // 8
self.buffer = bytearray(self.pages * self.width)
super().__init__(self.buffer, self.width, self.height, framebuf.MONO_VLSB)
self.init_display()
def init_display(self):
for cmd in (
SET_DISP, # display off
# address setting
SET_MEM_ADDR,
0x00, # horizontal
# resolution and layout
SET_DISP_START_LINE, # start at line 0
SET_SEG_REMAP | 0x01, # column addr 127 mapped to SEG0
SET_MUX_RATIO,
self.height – 1,
SET_COM_OUT_DIR | 0x08, # scan from COM[N] to COM0
SET_DISP_OFFSET,
0x00,
SET_COM_PIN_CFG,
0x02 if self.width > 2 * self.height else 0x12,
# timing and driving scheme
SET_DISP_CLK_DIV,
0x80,
SET_PRECHARGE,
0x22 if self.external_vcc else 0xF1,
SET_VCOM_DESEL,
0x30, # 0.83*Vcc
# display
SET_CONTRAST,
0xFF, # maximum
SET_ENTIRE_ON, # output follows RAM contents
SET_NORM_INV, # not inverted
SET_IREF_SELECT,
0x30, # enable internal IREF during display on
# charge pump
SET_CHARGE_PUMP,
0x10 if self.external_vcc else 0x14,
SET_DISP | 0x01, # display on
): # on
self.write_cmd(cmd)
self.fill(0)
self.show()
def poweroff(self):
self.write_cmd(SET_DISP)
def poweron(self):
self.write_cmd(SET_DISP | 0x01)
def contrast(self, contrast):
self.write_cmd(SET_CONTRAST)
self.write_cmd(contrast)
def invert(self, invert):
self.write_cmd(SET_NORM_INV | (invert & 1))
def rotate(self, rotate):
self.write_cmd(SET_COM_OUT_DIR | ((rotate & 1) << 3))
self.write_cmd(SET_SEG_REMAP | (rotate & 1))
def show(self):
x0 = 0
x1 = self.width – 1
if self.width != 128:
# narrow displays use centred columns
col_offset = (128 – self.width) // 2
x0 += col_offset
x1 += col_offset
self.write_cmd(SET_COL_ADDR)
self.write_cmd(x0)
self.write_cmd(x1)
self.write_cmd(SET_PAGE_ADDR)
self.write_cmd(0)
self.write_cmd(self.pages – 1)
self.write_data(self.buffer)
class SSD1306_I2C(SSD1306):
def __init__(self, width, height, i2c, addr=0x3C, external_vcc=False):
self.i2c = i2c
self.addr = addr
self.temp = bytearray(2)
self.write_list = [b”\x40″, None] # Co=0, D/C#=1
super().__init__(width, height, external_vcc)
def write_cmd(self, cmd):
self.temp[0] = 0x80 # Co=1, D/C#=0
self.temp[1] = cmd
self.i2c.writeto(self.addr, self.temp)
def write_data(self, buf):
self.write_list[1] = buf
self.i2c.writevto(self.addr, self.write_list)
class SSD1306_SPI(SSD1306):
def __init__(self, width, height, spi, dc, res, cs, external_vcc=False):
self.rate = 10 * 1024 * 1024
dc.init(dc.OUT, value=0)
res.init(res.OUT, value=0)
cs.init(cs.OUT, value=1)
self.spi = spi
self.dc = dc
self.res = res
self.cs = cs
import time
self.res(1)
time.sleep_ms(1)
self.res(0)
time.sleep_ms(10)
self.res(1)
super().__init__(width, height, external_vcc)
def write_cmd(self, cmd):
self.spi.init(baudrate=self.rate, polarity=0, phase=0)
self.cs(1)
self.dc(0)
self.cs(0)
self.spi.write(bytearray([cmd]))
self.cs(1)
def write_data(self, buf):
self.spi.init(baudrate=self.rate, polarity=0, phase=0)
self.cs(1)
self.dc(1)
self.cs(0)
self.spi.write(buf)
self.cs(1)
Micropython Src Code
from machine import Pin, I2C
import ssd1306
from time import sleep
# ESP32 Pin assignment
i2c = I2C(-1, scl=Pin(5), sda=Pin(4))
oled_width = 128
oled_height = 64
oled = ssd1306.SSD1306_I2C(oled_width, oled_height, i2c)
oled.text(‘Welcome’, 0, 0)
oled.text(‘OLED Display’, 0, 10)
oled.text(‘welcome to iottrends.tech’, 0, 20)
oled.text(‘I am READY!! When you are?’, 0, 30)
oled.show()
Sample Output.
Welcome
OLED Display
Welcome to iottrends.tech
I am READY!! When you are?
Code Explanation
import ssd1306
This imports the OLED Library that was uploaded previously to the Board.
i2c = I2C(-1, scl=Pin(5), sda=Pin(4))
We are defining the I2C Pins of ESP32 Board here. The ESP32 default I2C pins are GPIO22 (SCL) and GPIO21 (SDA). In case of MakePython ESP32 Board, the GPIO Pins are GPIO5 (SCL) and GPIO4 (SDA)
oled_width = 128
oled_height = 64
This line defines the OLED height and width
oled = ssd1306.SSD1306_I2C(oled_width, oled_height, i2c)
Then we create an SSD1306_I2C object called oled. This object accepts the OLED width, height, and the I2C pins defined earlier.
oled.text(‘Welcome’, 0, 0)
oled.text(‘OLED Display’, 0, 10)
Using oled we are initializing the OLED display & using the text() function we are write text.
oled.show()
Using this line we call the show() method to update the OLED.
It’s an remarkable piece of writing in favor of all the internet visitors;
they will take advantage from it I am sure.
I could not resist commenting. Exceptionally well written!