I2C | Technology Tutorials

A challenge in many Arduino projects is that it can be difficult to get I2C components working properly. Many times the libraries and demonstration code indicate a certain I2C address for the component, but the Arduino is unable to find the component at that Address. This can be a challenge, because often times we might not have the exact same version of the component that is assumed in the libraries and code. A perfect example of this are the SSD1306 OLED displays. Many of the components look identical, but they can have different I2C addresses. In order to overcome this challenge, the following code allows you to scan your I2C Bus, and list the address of all the components found. Simply attach the component as instructed in the component documentation. Then run the following code. It will list the address of the I2C components it finds. Then you can edit the sample code to use the proper address. Enjoy!

#include <Wire.h>
#define myWire Wire
int numDevices;
byte error, address;
void setup() {
  myWire.begin();
  Serial.begin(9600);
  Serial.println("Find I2C Devices: ");
}
void loop() {
  Serial.println("Scanning...");
  numDevices = 0;
  for (address = 1; address < 127; address=address+1) {
    myWire.beginTransmission(address);
    error = myWire.endTransmission();
    if (error == 0) {
      Serial.print("I2C device found at address 0x");
      if (address < 16)
        Serial.print("0");
      Serial.print(address, HEX);
      Serial.println("  !");
      numDevices = numDevices + 1;
    } else if (error == 4) {
      Serial.print("Unknown error at address 0x");
      if (address < 16)
        Serial.print("0");
      Serial.println(address, HEX);
    }
  }
  if (numDevices == 0)
    Serial.println("No I2C devices found");
  delay(5000);  
}

#include <Wire.h>

#define myWire Wire

int numDevices;

byte error, address;

void setup() {

myWire.begin();

Serial.begin(9600);

Serial.println("Find I2C Devices: ");

}

void loop() {

Serial.println("Scanning...");

numDevices = 0;

for (address = 1; address < 127; address=address+1) {

myWire.beginTransmission(address);

error = myWire.endTransmission();

if (error == 0) {

Serial.print("I2C device found at address 0x");

if (address < 16)

Serial.print("0");

Serial.print(address, HEX);

Serial.println(" !");

numDevices = numDevices + 1;

} else if (error == 4) {

Serial.print("Unknown error at address 0x");

if (address < 16)

Serial.print("0");

Serial.println(address, HEX);

}

if (numDevices == 0)

Serial.println("No I2C devices found");

delay(5000);

}

This lesson shows how to connect an LCD1602 to a Raspberry Pi using only 4 wires by I2C. You will need to copy the code below, and create a program called LCD1602.py, and save it in the same folder your main python programs are in.

#!/usr/bin/env python3

import time
import smbus2 as smbus

BUS = smbus.SMBus(1)

def write_word(addr, data):
    global BLEN
    temp = data
    if BLEN == 1:
        temp |= 0x08
    else:
        temp &= 0xF7
    BUS.write_byte(addr ,temp)

def send_command(comm):
    # Send bit7-4 firstly
    buf = comm & 0xF0
    buf |= 0x04               # RS = 0, RW = 0, EN = 1
    write_word(LCD_ADDR ,buf)
    time.sleep(0.002)
    buf &= 0xFB               # Make EN = 0
    write_word(LCD_ADDR ,buf)

    # Send bit3-0 secondly
    buf = (comm & 0x0F) << 4
    buf |= 0x04               # RS = 0, RW = 0, EN = 1
    write_word(LCD_ADDR ,buf)
    time.sleep(0.002)
    buf &= 0xFB               # Make EN = 0
    write_word(LCD_ADDR ,buf)

def send_data(data):
    # Send bit7-4 firstly
    buf = data & 0xF0
    buf |= 0x05               # RS = 1, RW = 0, EN = 1
    write_word(LCD_ADDR ,buf)
    time.sleep(0.002)
    buf &= 0xFB               # Make EN = 0
    write_word(LCD_ADDR ,buf)

    # Send bit3-0 secondly
    buf = (data & 0x0F) << 4
    buf |= 0x05               # RS = 1, RW = 0, EN = 1
    write_word(LCD_ADDR ,buf)
    time.sleep(0.002)
    buf &= 0xFB               # Make EN = 0
    write_word(LCD_ADDR ,buf)

def init(addr, bl):
#    global BUS
#    BUS = smbus.SMBus(1)
    global LCD_ADDR
    global BLEN
    LCD_ADDR = addr
    BLEN = bl
    try:
        send_command(0x33) # Must initialize to 8-line mode at first
        time.sleep(0.005)
        send_command(0x32) # Then initialize to 4-line mode
        time.sleep(0.005)
        send_command(0x28) # 2 Lines & 5*7 dots
        time.sleep(0.005)
        send_command(0x0C) # Enable display without cursor
        time.sleep(0.005)
        send_command(0x01) # Clear Screen
        BUS.write_byte(LCD_ADDR, 0x08)
    except:
        return False
    else:
        return True

def clear():
    send_command(0x01) # Clear Screen

def openlight():  # Enable the backlight
    BUS.write_byte(0x27,0x08)
    BUS.close()

def write(x, y, str):
    if x < 0:
        x = 0
    if x > 15:
        x = 15
    if y <0:
        y = 0
    if y > 1:
        y = 1

    # Move cursor
    addr = 0x80 + 0x40 * y + x
    send_command(addr)

    for chr in str:
        send_data(ord(chr))

if __name__ == '__main__':
    init(0x27, 1)
    write(4, 0, 'Hello')
    write(7, 1, 'world!')

100

101

#!/usr/bin/env python3

import time

import smbus2 as smbus

BUS = smbus.SMBus(1)

def write_word(addr, data):

global BLEN

temp = data

if BLEN == 1:

temp |= 0x08

else:

temp &= 0xF7

BUS.write_byte(addr ,temp)

def send_command(comm):

# Send bit7-4 firstly

buf = comm & 0xF0

buf |= 0x04 # RS = 0, RW = 0, EN = 1

write_word(LCD_ADDR ,buf)

time.sleep(0.002)

buf &= 0xFB # Make EN = 0

write_word(LCD_ADDR ,buf)

# Send bit3-0 secondly

buf = (comm & 0x0F) << 4

buf |= 0x04 # RS = 0, RW = 0, EN = 1

write_word(LCD_ADDR ,buf)

time.sleep(0.002)

buf &= 0xFB # Make EN = 0

write_word(LCD_ADDR ,buf)

def send_data(data):

# Send bit7-4 firstly

buf = data & 0xF0

buf |= 0x05 # RS = 1, RW = 0, EN = 1

write_word(LCD_ADDR ,buf)

time.sleep(0.002)

buf &= 0xFB # Make EN = 0

write_word(LCD_ADDR ,buf)

# Send bit3-0 secondly

buf = (data & 0x0F) << 4

buf |= 0x05 # RS = 1, RW = 0, EN = 1

write_word(LCD_ADDR ,buf)

time.sleep(0.002)

buf &= 0xFB # Make EN = 0

write_word(LCD_ADDR ,buf)

def init(addr, bl):

# global BUS

# BUS = smbus.SMBus(1)

global LCD_ADDR

global BLEN

LCD_ADDR = addr

BLEN = bl

try:

send_command(0x33) # Must initialize to 8-line mode at first

time.sleep(0.005)

send_command(0x32) # Then initialize to 4-line mode

time.sleep(0.005)

send_command(0x28) # 2 Lines & 5*7 dots

time.sleep(0.005)

send_command(0x0C) # Enable display without cursor

time.sleep(0.005)

send_command(0x01) # Clear Screen

BUS.write_byte(LCD_ADDR, 0x08)

except:

return False

else:

return True

def clear():

send_command(0x01) # Clear Screen

def openlight(): # Enable the backlight

BUS.write_byte(0x27,0x08)

BUS.close()

def write(x, y, str):

if x < 0:

x = 0

if x > 15:

x = 15

if y <0:

y = 0

if y > 1:

y = 1

# Move cursor

addr = 0x80 + 0x40 * y + x

send_command(addr)

for chr in str:

send_data(ord(chr))

if __name__ == '__main__':

init(0x27, 1)

write(4, 0, 'Hello')

write(7, 1, 'world!')

Making The World a Better Place One High Tech Project at a Time. Enjoy!

Technology Tutorials

Tag Archives: I2C

Scan Arduino to Find I2C Addresses

Library for I2C Connection of the LCD1602 to the Raspberry PI

Making The World a Better Place One High Tech Project at a Time. Enjoy!