februariusx
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4x20 lcd connection

Tue Sep 22, 2015 8:51 am

hi ,

im new in rasp world,

i have some question in connecting 4x20 LCD on raspberry pi 2 model b GPIO,

i cannot post a display on LCD , i dont know if my connection are not correct

im just replacing my old system MCU to Raspberry

BMS Doug
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Re: 4x20 lcd connection

Tue Sep 22, 2015 11:38 am

please describe how you are attempting to connect the 4x20 display to the Pi.

Pictures would be useful (you will need to post them on an image hosting site and supply a link to the picture in the thread).
Doug.
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ame
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Re: 4x20 lcd connection

Tue Sep 22, 2015 12:08 pm

Here's a working example:
http://www.raspberrypi-spy.co.uk/2012/0 ... ng-python/

Does it help?

Massi
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Re: 4x20 lcd connection

Tue Sep 22, 2015 12:45 pm

februariusx wrote:hi ,

im new in rasp world,

i have some question in connecting 4x20 LCD on raspberry pi 2 model b GPIO,

i cannot post a display on LCD , i dont know if my connection are not correct

im just replacing my old system MCU to Raspberry
if it's a hd44780 based display, you can find tons of schematics and code on google..
(one example is the link ame posted)


raycarter
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Re: 4x20 lcd connection

Wed Sep 23, 2015 10:38 pm

Try this link:
https://learn.adafruit.com/character-lc ... k?view=all

It shows a 16x2, but the wiring is the same. Adafruit also has an LCD 'backpack' that makes it useable via i2c or spi - only 4 wires for i2c or 5 for spi.

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mikronauts
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Re: 4x20 lcd connection

Wed Sep 23, 2015 10:44 pm

You can also try following my article:

http://www.mikronauts.com/raspberry-pi/ ... terfacing/
http://Mikronauts.com - home of EZasPi, RoboPi, Pi Rtc Dio and Pi Jumper @Mikronauts on Twitter
Advanced Robotics, I/O expansion and prototyping boards for the Raspberry Pi

februariusx
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Joined: Tue Sep 22, 2015 8:37 am

Re: 4x20 lcd connection

Thu Sep 24, 2015 3:31 am

thanks for replies

i did your samples,

but my lcd dosent posting display

is there compatibility should be considerate between dot matrix lcd and rpi?

anyway i try some scripts based on the links

it given me segmentation fault

current i run my RPI with debian/ubuntu vice-versa , it is because i have already running apps in there from i386 and already migrated to arm, only i need is the display out to lcd and rs232 later

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mahjongg
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Re: 4x20 lcd connection

Thu Sep 24, 2015 10:57 am

One compatibility problem, could be that the PI outputs 3.3V logic high levels, and for many LCD controllers 3.3V is not enough, they need at least 3.5V (70% of VCC).
To prevent the need to use level converters for all the control lines, you can lower VCC from 5.0V to 4.5V, by using a diode to drop 0.5V. Simply put a small diode (1N4148) in between the 5V and the VCC of the display.

februariusx
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Re: 4x20 lcd connection

Wed Sep 30, 2015 2:02 am

hi everyone

i bought 2x16 liner 1602A lcd ,

and their it is

https://lh3.googleusercontent.com/-tt2D ... 7510_n.jpg

and still the sample scripts dosent working

http://www.raspberrypi-spy.co.uk/2012/0 ... ng-python/

the previous issue with segmentation fault with raspberry debian jessie

now i reverted to raspberry debian wheezy , no more segmentation fault,

and my problem now , it still dosent displaying :(

Massi
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Re: 4x20 lcd connection

Wed Sep 30, 2015 7:30 am

lol, i love how you described your problem..
"not displaying"

btw, at least you should consider that your display has 6+5 connections, while usually it must have 6+6 connections..

for the rest, really "not displaying" is not a description and noone will help you in this way

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rpdom
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Re: 4x20 lcd connection

Wed Sep 30, 2015 10:01 am

You don't seem to have anything connected to pin 3 - the LCD contrast pin. Without that you might not be able to see the displayed text. Try looking at the display from a shallow angle - almost edge-on from the bottom edge - you might see some text or just square blocs on the display.

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DougieLawson
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Re: 4x20 lcd connection

Wed Sep 30, 2015 5:52 pm

Ideally, you need to connect the contrast pin to the wiper of a 10K trimpot (wired between 5V0 and GND) and adjust that until the display appears. If you don't have a trimpot try a series of 1K resistors.
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februariusx
Posts: 7
Joined: Tue Sep 22, 2015 8:37 am

Re: 4x20 lcd connection

Thu Oct 01, 2015 8:48 am

hi guy,

thanks for help

i already did work

i added 10k potentiometer on 3rd pin contrast

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