TheBackShed.com

Forum Index : Microcontroller and PC projects : 16x2 LCD Display (1602A) on Picomite

Author

Message

Bleep
Guru

Joined: 09/01/2022
Location: United Kingdom
Posts: 512

Posted: 12:01pm 13 Mar 2023

Copy link to clipboard

Print this post

Hi, I'm trying to drive one of these 1602A LCD devices :-

BITBANG LCD INIT GP8, GP9, GP10, GP11, GP6, GP7
BITBANG LCD clear
BITBANG LCD 1, 1, "Hello World"

It claims to use the HD44780 driver chip, however I am failing to drive it, does the display have to be a 3.3V device? in the diagram in the manual, it shows 5V supply, I did in fact order a 3.3V and this one arrived however on further investigation, I think it is 5V, though it is not entirely clear how you tell?
I have checked the outputs from the Pico and all of the EN,RS,D7,D6,D5,D4 signals are toggling in what appears to be a sensible way when the display is driven.
Any suggestions?
Regards, Kevin.

atmega8

Guru

Joined: 19/11/2013
Location: Germany
Posts: 722

Posted: 12:37pm 13 Mar 2023

Copy link to clipboard

Print this post

This code works for me "out of the box" with a Picomite, direct from Commandline
In most cases it is wrong cabling, wrong (missing) contrast Potentiometer.....
Powered with 5 Volt from the PICO.

Bitbang LCD INIT GP2,GP3,GP4,GP5,GP6,GP7
Bitbang LCD 1,1," Hello World"
> print mm.ver
5.0706

Volhout
Guru

Joined: 05/03/2018
Location: Netherlands
Posts: 4256

Posted: 01:00pm 13 Mar 2023

Copy link to clipboard

Print this post

@Bleep

1/ You have the contrast set with fixed values (fixed resistors). That could be a problem, since there is quite some spread between displays (I use a potmeter, and sometimes it is really over to one side).

2/ No backlight. May makke it more difficult.

3/ The ones I have used are all 5V.

4/ Check if you have a swap in the datalines. For the text on screen: you will just see different characters, be before the text is shown, the same 4 data lines are used to configure the display (config depending RS pin level). A swap in datalines may cause wrong configuration of the display.

Regards,

Volhout

PicomiteVGA PETSCII ROBOTS

Bleep
Guru

Joined: 09/01/2022
Location: United Kingdom
Posts: 512

Posted: 03:13pm 13 Mar 2023

Copy link to clipboard

Print this post

Thanks everyone,
Particular thanks to Volhout, again, you were quite correct, it was the contrast and yes it had to be set right down to almost ground, then suddenly the display appeared. :-)
Thank you very much.
Regards, Kevin.

atmega8

Guru

Joined: 19/11/2013
Location: Germany
Posts: 722

Posted: 05:12pm 13 Mar 2023

Copy link to clipboard

Print this post

atmega8 said This code works for me "out of the box" with a Picomite, direct from Commandline
In most cases it is wrong cabling, wrong (missing) contrast Potentiometer.....
Powered with 5 Volt from the PICO.

Bitbang LCD INIT GP2,GP3,GP4,GP5,GP6,GP7
Bitbang LCD 1,1," Hello World"
> print mm.ver
5.0706

Volhout
Guru

Joined: 05/03/2018
Location: Netherlands
Posts: 4256

Posted: 05:48pm 13 Mar 2023

Copy link to clipboard

Print this post

And atmega8.....

PicomiteVGA PETSCII ROBOTS

Print this page

To reply to this topic, you need to log in.