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    Please do not post a support request without first reading and following the advice in https://retropie.org.uk/forum/topic/3/read-this-first

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

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    hd44780 16x2 lc
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    • cyperghostC
      cyperghost
      last edited by

      @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!

      img

      1 Reply Last reply Reply Quote 0
      • BozB
        Boz
        last edited by 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.

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        • cyperghostC
          cyperghost
          last edited by 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)
          
          1 Reply Last reply Reply Quote 1
          • BozB
            Boz
            last edited by

            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!!

            1 Reply Last reply Reply Quote 1
            • cyperghostC
              cyperghost
              last edited by cyperghost

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

              BozB 1 Reply Last reply Reply Quote 0
              • BozB
                Boz @cyperghost
                last edited by 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.

                1 Reply Last reply Reply Quote 0
                • BozB
                  Boz
                  last edited by 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?)

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                  • cyperghostC
                    cyperghost
                    last edited by 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.

                    1 Reply Last reply Reply Quote 1
                    • BozB
                      Boz
                      last edited by 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.

                      1 Reply Last reply Reply Quote 0
                      • cyperghostC
                        cyperghost
                        last edited by 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
                        img

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

                        1 Reply Last reply Reply Quote 1
                        • BozB
                          Boz
                          last edited by

                          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?

                          1 Reply Last reply Reply Quote 0
                          • BozB
                            Boz
                            last edited by

                            Here's some pics:

                            0_1501408883945_1.JPG

                            0_1501408926255_2.JPG

                            0_1501408994184_3.JPG

                            0_1501409012372_4.JPG

                            1 Reply Last reply Reply Quote 0
                            • BozB
                              Boz
                              last edited by

                              I have it wired like so:

                              LV (red) to pin1 on dac
                              HV (orange) to pin2 on dac
                              GND (grey) to pin6 on dac
                              GND (grey) to GND on i2c
                              LV1 (blue) to pin3 on dac
                              LV2 (yellow) to pin 5 on dac
                              HV1 (blue) to SDA on i2c
                              HV2 (yellow) to SDL on i2c

                              Nothing connected to VCC on i2c.

                              1 Reply Last reply Reply Quote 0
                              • cyperghostC
                                cyperghost
                                last edited by cyperghost

                                Can you measure voltage on HV? That has to be 5,0V
                                Then connect HV also to VCC on your I2C LCD - with 5,0V

                                The connection HV and LV on level shifter is only for internal comparism 3,3V and 5V it is not intended as supply. The LCD must glow if the there is 5,0V...
                                The Pi got annothe 5V pin... Pin2! Use that for LCD connect!

                                EDIT: Sorry Pin 2 is already used... Can you expand it? Or what about Pin 4? You need 5V for the LCD!

                                1 Reply Last reply Reply Quote 0
                                • BozB
                                  Boz
                                  last edited by Boz

                                  Ok so I just add a wire from pin 4 on pi(dac) to vcc on i2c and leave the rest?

                                  I thought the idea was to not directly connect 5v power to the i2c backpack ?

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                                  • cyperghostC
                                    cyperghost
                                    last edited by cyperghost

                                    Yes
                                    But I'm not sure if the device can be detected. I2C is multibus so it should work.... but we will see. Maybe I2C adresses from your devices are the same. Just connect and report!
                                    Your have a seconds Pi.... maybe you can get it on this to work?

                                    1 Reply Last reply Reply Quote 0
                                    • BozB
                                      Boz
                                      last edited by Boz

                                      Will connecting pin4 directly to the lcd not damage the pi?
                                      I thought that was the reason I got the level shifter?

                                      If I was to solder a 2nd wire to HV header on the level shifter and connect that wire to VCC on the i2c would that solve the problem?

                                      1 Reply Last reply Reply Quote 0
                                      • cyperghostC
                                        cyperghost
                                        last edited by cyperghost

                                        No...
                                        There are voltage output pins!
                                        2x 5V and 2x 3,3V ... The 5V can output the same amount as the power supply so very robust
                                        the 3,3V can only output 40 or 60mA that's enough vor LEDs or a few IC.

                                        The rest are "sender" and/or "receiver" Pins.
                                        They sending with 3,3V and if they are receiving data the voltage level should also 3,3V
                                        5,0V is much to high... So the level shifter reduces or highers only the "sender" and "receiver" parts. It has nothing to do with the power supply. Got it?

                                        You can also try to split the Pin1 to work with level shifter and LCD.

                                        1 Reply Last reply Reply Quote 1
                                        • BozB
                                          Boz
                                          last edited by

                                          Thanks now I understand,
                                          I'll solder a wire onto the HV pin then and see what happens :)

                                          LV (red) to pin1 on dac
                                          HV (orange) to pin2 on dac / VCC on i2c
                                          GND (grey) to pin6 on dac
                                          GND (grey) to GND on i2c
                                          LV1 (blue) to pin3 on dac
                                          LV2 (yellow) to pin 5 on dac
                                          HV1 (blue) to SDA on i2c
                                          HV2 (yellow) to SDL on i2c

                                          1 Reply Last reply Reply Quote 0
                                          • cyperghostC
                                            cyperghost
                                            last edited by

                                            Yes ... Seems right now

                                            1 Reply Last reply Reply Quote 0
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