What am i doing wrong with my hd44780 16x2 lcd?

Boz

So i just swap pin 4 for pin 1?

Boz

I feel which ever method i choose i should remove the dac and connect directly to the pi. Even though the lcd was connected without a level shifter it still had power...so the reason why i get no address from i2cdetect -y 1 must be because either the gpio input was damaged or the header on the dac isn't soldered very well.
Removing the dac narrows it down i reckon.

cyperghost

@boz said in What am i doing wrong with my hd44780 16x2 lcd?:

So i just swap pin 4 for pin 1?

Yes this will not overvoltage SDL/SDA ... If the red LED is on then the backpack could work and may be detected. With much much luck your display will also run!

With this config my I2S device results this

pi@raspberrypi:~ $ i2cdetect -y 1
     0  1  2  3  4  5  6  7  8  9  a  b  c  d  e  f
00:          -- -- -- -- -- -- -- -- -- -- -- -- --
10: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
20: -- -- -- -- -- -- -- 27 -- -- -- -- -- -- -- --
30: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
40: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
50: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
60: -- -- -- -- -- -- -- -- -- -- -- -- -- -- -- --
70: -- -- -- -- -- -- -- --

Boz

Ha ha we'll see!

Boz

Tried with 3.3v pin, backpack gets power but still no address. Will try this again over the weekend but connected directly to the pi.

cyperghost

@Boz Maybe you remove your I2S devices, too and look to the posting @future-child gave you. This is a nice instruction as well

Boz

Thanks, I'll spend some time fault finding/process of elimination. I'll try all the things you guy's have suggested and see how i get on.

Boz

Success!!
I dug out an old rpi2 and tried the display on that using i2c (3.3v). I got an address from i2cdetect -y 1.... (3f) and changed a few test scripts to suit all of which worked.
I want on to change the script I was going to use in my build (retropie_clcd.py) and then altered all the text to what I wanted.
Tried everything that I'd just done exactly the same on my rpi3 with dac etc and still no address. So it has to be the dac for whatever reason, I'll connect the lcd directly to the rpi3 with no dac attached see if that works.

cyperghost

@Boz - Don't give up!
I was in luck, on my work we used former HD44780 display for giving text messages to consumer, so I soldered my I2S-backbag to this and it works like a charm. Anyway the characters don't look good

Hello RetroPie!
Greetings from
  cyperghost
  & crcerror

It's an 16x4 display and it worked fine with level shifter!

Boz

No I won't give up, I used the sd card from the rpi2 (where the lcd was working) and stuck it in the rpi3 with no dac attached and bingo!!
So now I'm going to reconnect the dac and try that. If that works also I know it's not a hardware issue :)
I'll start with a fresh image then add the ATXraspi and test lcd, add the DAC then test lcd.....and so on until either I find out the problem or it just works (and I never find out what the problem was)
Level shifter getting delivered this week hopefully.

cyperghost

@Boz
I used the python libary posted here - it worked flawless with my setup. Keep care of upper and lower cases. Just use the same filenames as posted in the thread.

Good luck mate

EDIT:

Just for conserving (INTERNET IS FLUID!)
Testing python sniplet retropie.py

import I2C_LCD_driver
from time import *

mylcd = I2C_LCD_driver.lcd()

mylcd.lcd_display_string("Hello RetroPie!", 1)
mylcd.lcd_display_string("Column 3!", 2, 3)

LCD driverlibary I2C_LCD_driver.py - change adress in driver for ex 0x27h
Please check with i2cdetect -y 1 (or i2cdetect -y 0 on Raspberry v1 B)

# -*- coding: utf-8 -*-
# Original code found at:
# https://gist.github.com/DenisFromHR/cc863375a6e19dce359d

"""
Compiled, mashed and generally mutilated 2014-2015 by Denis Pleic
Made available under GNU GENERAL PUBLIC LICENSE

# Modified Python I2C library for Raspberry Pi
# as found on http://www.recantha.co.uk/blog/?p=4849
# Joined existing 'i2c_lib.py' and 'lcddriver.py' into a single library
# added bits and pieces from various sources
# By DenisFromHR (Denis Pleic)
# 2015-02-10, ver 0.1

"""

# i2c bus (0 -- original Pi, 1 -- Rev 2 Pi)
I2CBUS = 1

# LCD Address
ADDRESS = 0x27

import smbus
from time import sleep

class i2c_device:
   def __init__(self, addr, port=I2CBUS):
      self.addr = addr
      self.bus = smbus.SMBus(port)

# Write a single command
   def write_cmd(self, cmd):
      self.bus.write_byte(self.addr, cmd)
      sleep(0.0001)

# Write a command and argument
   def write_cmd_arg(self, cmd, data):
      self.bus.write_byte_data(self.addr, cmd, data)
      sleep(0.0001)

# Write a block of data
   def write_block_data(self, cmd, data):
      self.bus.write_block_data(self.addr, cmd, data)
      sleep(0.0001)

# Read a single byte
   def read(self):
      return self.bus.read_byte(self.addr)

# Read
   def read_data(self, cmd):
      return self.bus.read_byte_data(self.addr, cmd)

# Read a block of data
   def read_block_data(self, cmd):
      return self.bus.read_block_data(self.addr, cmd)


# commands
LCD_CLEARDISPLAY = 0x01
LCD_RETURNHOME = 0x02
LCD_ENTRYMODESET = 0x04
LCD_DISPLAYCONTROL = 0x08
LCD_CURSORSHIFT = 0x10
LCD_FUNCTIONSET = 0x20
LCD_SETCGRAMADDR = 0x40
LCD_SETDDRAMADDR = 0x80

# flags for display entry mode
LCD_ENTRYRIGHT = 0x00
LCD_ENTRYLEFT = 0x02
LCD_ENTRYSHIFTINCREMENT = 0x01
LCD_ENTRYSHIFTDECREMENT = 0x00

# flags for display on/off control
LCD_DISPLAYON = 0x04
LCD_DISPLAYOFF = 0x00
LCD_CURSORON = 0x02
LCD_CURSOROFF = 0x00
LCD_BLINKON = 0x01
LCD_BLINKOFF = 0x00

# flags for display/cursor shift
LCD_DISPLAYMOVE = 0x08
LCD_CURSORMOVE = 0x00
LCD_MOVERIGHT = 0x04
LCD_MOVELEFT = 0x00

# flags for function set
LCD_8BITMODE = 0x10
LCD_4BITMODE = 0x00
LCD_2LINE = 0x08
LCD_1LINE = 0x00
LCD_5x10DOTS = 0x04
LCD_5x8DOTS = 0x00

# flags for backlight control
LCD_BACKLIGHT = 0x08
LCD_NOBACKLIGHT = 0x00

En = 0b00000100 # Enable bit
Rw = 0b00000010 # Read/Write bit
Rs = 0b00000001 # Register select bit

class lcd:
   #initializes objects and lcd
   def __init__(self):
      self.lcd_device = i2c_device(ADDRESS)

      self.lcd_write(0x03)
      self.lcd_write(0x03)
      self.lcd_write(0x03)
      self.lcd_write(0x02)

      self.lcd_write(LCD_FUNCTIONSET | LCD_2LINE | LCD_5x8DOTS | LCD_4BITMODE)
      self.lcd_write(LCD_DISPLAYCONTROL | LCD_DISPLAYON)
      self.lcd_write(LCD_CLEARDISPLAY)
      self.lcd_write(LCD_ENTRYMODESET | LCD_ENTRYLEFT)
      sleep(0.2)


   # clocks EN to latch command
   def lcd_strobe(self, data):
      self.lcd_device.write_cmd(data | En | LCD_BACKLIGHT)
      sleep(.0005)
      self.lcd_device.write_cmd(((data & ~En) | LCD_BACKLIGHT))
      sleep(.0001)

   def lcd_write_four_bits(self, data):
      self.lcd_device.write_cmd(data | LCD_BACKLIGHT)
      self.lcd_strobe(data)

   # write a command to lcd
   def lcd_write(self, cmd, mode=0):
      self.lcd_write_four_bits(mode | (cmd & 0xF0))
      self.lcd_write_four_bits(mode | ((cmd << 4) & 0xF0))

   # write a character to lcd (or character rom) 0x09: backlight | RS=DR<
   # works!
   def lcd_write_char(self, charvalue, mode=1):
      self.lcd_write_four_bits(mode | (charvalue & 0xF0))
      self.lcd_write_four_bits(mode | ((charvalue << 4) & 0xF0))
  
   # put string function with optional char positioning
   def lcd_display_string(self, string, line=1, pos=0):
    if line == 1:
      pos_new = pos
    elif line == 2:
      pos_new = 0x40 + pos
    elif line == 3:
      pos_new = 0x14 + pos
    elif line == 4:
      pos_new = 0x54 + pos

    self.lcd_write(0x80 + pos_new)

    for char in string:
      self.lcd_write(ord(char), Rs)

   # clear lcd and set to home
   def lcd_clear(self):
      self.lcd_write(LCD_CLEARDISPLAY)
      self.lcd_write(LCD_RETURNHOME)

   # define backlight on/off (lcd.backlight(1); off= lcd.backlight(0)
   def backlight(self, state): # for state, 1 = on, 0 = off
      if state == 1:
         self.lcd_device.write_cmd(LCD_BACKLIGHT)
      elif state == 0:
         self.lcd_device.write_cmd(LCD_NOBACKLIGHT)

   # add custom characters (0 - 7)
   def lcd_load_custom_chars(self, fontdata):
      self.lcd_write(0x40);
      for char in fontdata:
         for line in char:
            self.lcd_write_char(line)

Boz

Thanks m8,
i'll try that script when my level shifter comes, my displays a little dull at the minute on 3.3v.
Now I know the display can work, I'll implement it into the facia design. The lcd wasn't essential but damn it looks good!!

cyperghost

@Boz Post pictures if you're ready with your build :)

Boz

@cyperghost will do m8, the level shifter came today so I'm gonna wire it up tomorrow if I get time. I'll post pics of the display working but it might be a while for the finished product.
I need a day when my boss isn't in so I can mill the facia.
Thanks for your time aswell m8, it's been much appreciated. You and future.child.

Boz

Hi, I'm about to wire up this level shifter but I'm a bit confused on the wiring.
Is this right so far?

Level Shifter/ Pi / LCD
LV / pin 1 (LV from level shifter to pin 1 on pi)
LV1 / pin 3 (LV1 from level shifter to pin 3 on pi)
LV2 / pin 5 (LV2 from level shifter to pin 5 on pi)
GND / pin 6 / GND (gnd from level shifter to pin6 on pi, opposite gnd on level
shifter to gnd on LCD?)
HV / pin 2 / VCC (HV from level shifter to pin 2 on pi, then?)
HV1 / SDA (HV1 from level shifter to SDA on i2c?)
HV2 / SCL (HV2 from level shifter to SCL on i2c?)

cyperghost

@Boz You are 100% on the right track :)

L means Low
H means High

L1 = 3,3V and is connected to your Pi power Pin 1
H1 = 5,0V and is connected to your Pi power Pin 2
G = Ground connected to your Pi (3,3V and 5,0V and of course also LCD via Levelshifter)

LV1 = SDA Pin 3 from your Pi
LV2 = SDL Pin 5 from your Pi

HV1 = SDA to your I2C LCD
HV2 = SDL to your I2C LCD

GND is GND and doesn't matter were you connect to your Pi because voltage potential is equal!

~~You connect Ground from LCD to your Pi, also the 3,3V and 5,0V are connected to your Pi. You can see~~ picture in my posting

Usually you can connect all grounds together. ~~But at first try I would use 3,3V/Ground and 5,0V/Ground seperate because they are needed to reference voltage level.~~

Boz

So I connect the levelshifter GND LV side (3.3v) to pin 6 (GND) on the pi and GND HV side (5v) to say pin 9 (GND) on the pi also? How do I also connect GND from the levelshifter to the lcd with no GND pins left?
(Please bear with me I don't have a brilliant understanding of voltage etc)
ps: I'm using direct wiring and no breadboard.

cyperghost

@Boz The best way is to connect every ground as single line - you will avoid interferences with that. But you can connect ground 3,3V to Pi ground and connect HV ground to I2C backpack.

But on the other hand (I didn't know you don't have a breakboard):
As they use all the some potential it isn't needed to wire every ground to annother point.
Here you see the shematics

I used one of my old B+ and used a Pi Dish but not for 25$ :))

Boz

I must have messed up somewhere there's no power to the lcd.
I have the wires connected as you said (will double check again in a min) but connected via the header on my dac.
I notice I didn't connect any wire to the vcc on the i2c backpack is this correct?

Boz

Here's some pics: