ATTiny85 I2C LCD

Question

My setup is as follows:

• Arduino IDE 1.6.11
• Arduino Pro Mini as ISP
• ATTiny85 1602A LCD with I2C board

The libraries I use are:

• TinyWireM (source: https://github.com/adafruit/TinyWireM)
• LiquidCrystal_I2C (modified for ATTiny) (source: http://playground.arduino.cc/Code/USIi2c)

The Sketch I use to test with:

#include <TinyWireM.h> 
#include <LiquidCrystal_I2C.h> 
LiquidCrystal_I2C lcd(0x3F,16,2); // set address & 16 chars / 2 lines
void setup()
{
 TinyWireM.begin(); // initialize I2C lib
 lcd.init(); // initialize the lcd 
 lcd.backlight(); 
 lcd.clear(); // Print a message to the LCD.
}
void loop()
{
 lcd.setCursor(0, 0);
 lcd.print("Hello World on Attiny85");
 delay(2000);
}

The address is 0x3F, I found this using the scanner sketch, I also tested the LCD using the Arduino Pro Mini directly, it works fine.

The result of this setup is a single line of black blocks. My guess is that the initialization failed in some way. I have tried some things to make it work:

• Pull-ups on SDA and SCL
• Isolated from Arduino with regulated power supply
• Setting contract with the pot meter on the back
• reinstall of PC
• reinstall of Arduino IDE
• 1MHz, 8Mhz, TinyCore default and High-Low Tech
• Replaced FTDI
• Replaced Tiny85
• Replaced LCD
• Replaced Arduino Pro Mini

Some pictures:

back of the display

the blocks

connections

[EDIT]

Final sketch:

#include <TinyWireM.h> // I2C Master lib for ATTinys which use USI
// #include <LiquidCrystal_I2C.h>
#include "LiquidCrystal_attiny.h"
LiquidCrystal_I2C lcd(0x27,16,2);
void setup() {
 // Now set up the LCD
 //lcd.begin(16,2); // initialize the lcd
 pinMode(4, OUTPUT);
 lcd.init();
 lcd.backlight();
 lcd.home (); // go home
 lcd.print("Weatherstation");
 lcd.setCursor ( 0, 1 ); // go to position
 lcd.print("BMP180");
 delay(2000);
}
void loop() {
 digitalWrite(4, HIGH);
 delay(100);
 digitalWrite(4, LOW);
 delay(100);
}

• Nick Gammon: Comments are not for extended discussion; this conversation has been moved to chat.
• Mero55: It looks like you did not connect the SCL line..... Make sure you're using the correct pins! they default to pin0 for SDA and pin2 for SCL.
• Nick Gammon: Please post further comments in the chat room above. Comments posted here are likely to be deleted.
• Dat Ha: Just a question, why do you want to use and ATtiny when you can just program any I2C with your Arduino??? P.S. Just trying to learn so no hate for this question please.
• Thijs: no problem, I will skip my usual hate-reply :) Nick may hate-reply for not using the chat box though, haha. I choose the ATTiny over the Arduino because my project will sleep a lot and use a battery 3.7V power source. ATTiny will run for weeks/months vs Arduino for days.

Answer 1

After hours of Googling, I found a blog post by Dimitris Platis where he describes using an ATTiny85 with I2C LCD. I emailed the guy and he replied with a link to his LCD I2C ATTiny library on GitHub. Using this library with the TinyWireM and the right core, it instantly worked.

My final setup is with a 4.7K resistor on SDA and SCL, I will add the final sketch in the original post under [EDIT]. This adventure took me two weeks so I hope it helps someone else some day.

LCD library used: https://github.com/platisd/ATtiny85-LCD-library
TinyWireM used: https://github.com/adafruit/TinyWireM
Core used: https://github.com/vprimachenko/ArduinoTiny

Answer 2

It doesn't look like you have an Arduino Pro Mini. I2C lines on a Pro Mini are on pins A4 for SDA and A5 for SCL and those 2 pins are placed at an odd location - check picture.

Hope I was helpful :)

Arduino Pro Mini pinout

• Nick Gammon: He is using an ATtiny85 to talk to the LCD. The other Arduino is just for programming - as far as I can tell.
• user27130: Well his Arduino seems still not like a Pro Mini so I don't know if it makes a difference.
• Thijs: you are right :) but it does not matter, as Nick said it is just a programmer
• Roberto Lo Giacco: I own a few of those, they are cheap Chinese clones, pins are located slightly differently.

Answer 3

I've spent an hour doing this problem and searched a lot. If you still didn't find the solution by doing this. Pls try to reduce the clock speed from Internal 8 MHz to Internal 1MHz. That way it works mine.