Discussion:
[lcd4linux] Is it possible to use LCD4Linux with a HD44780-compatible LCD, which is attached to the GPIO pins of a Raspberry Pi?
Prof. Dr. Christian Baun
2014-08-31 11:18:48 UTC
Permalink
Hi all,

is it possible to use LCD4Linux with a LCD (HD44780 compatible
controller), which is attached to the GPIO pins of a Raspberry Pi?

Has anybody here an example for a lcd4linux.conf file, which makes use
of the Raspberry Pi GPIO pins?

Best Regards
Christian
Michael Reinelt
2014-08-31 11:39:59 UTC
Permalink
Hello Christian,

as lcd4linux is a lot older than raspberry, I don't think that it will work, at least not out-of-the-box.

back in the "good old days" the only GPIO-like thing on a PC used to be the parallel port, and thats what a low-level
driver exists for (drv_generic_parport), which uses either extremely old school io instructions, or ppdev.

As I have absolutely no idea how GPIOs are controlled on a raspberyy, I cannot advice you how to implement it.

maybe using some kind of i2c-to-parallel chip could work, too.



regards, Michael
Post by Prof. Dr. Christian Baun
Hi all,
is it possible to use LCD4Linux with a LCD (HD44780 compatible
controller), which is attached to the GPIO pins of a Raspberry Pi?
Has anybody here an example for a lcd4linux.conf file, which makes use
of the Raspberry Pi GPIO pins?
Best Regards
Christian
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Johan Swenker
2014-08-31 18:49:21 UTC
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Hi,

I would like to disagree. Even though lcd4linux is older then the raspberry, the GPIO-pins of the raspberry are
as versatile as the parallel port of yesteryear.

Using a search engine you will find several people who have connected an LCD to the RPi. For example:
https://learn.adafruit.com/downloads/pdf/drive-a-16x2-lcd-directly-with-a-raspberry-pi.pdf
They even have software, though incompatibel with lcd4linux.

The same search engine will also be able to find you several LCDs with an I2C interface (implemented by
adding a microcontroller board to the LCD). Among them: http://www.bitwizard.nl/wiki/index.php/SPI_LCD

Regards Johan
Post by Michael Reinelt
Hello Christian,
as lcd4linux is a lot older than raspberry, I don't think that it will work, at least not out-of-the-box.
back in the "good old days" the only GPIO-like thing on a PC used to be the parallel port, and thats what a low-level
driver exists for (drv_generic_parport), which uses either extremely old school io instructions, or ppdev.
As I have absolutely no idea how GPIOs are controlled on a raspberyy, I cannot advice you how to implement it.
maybe using some kind of i2c-to-parallel chip could work, too.
regards, Michael
Post by Prof. Dr. Christian Baun
Hi all,
is it possible to use LCD4Linux with a LCD (HD44780 compatible
controller), which is attached to the GPIO pins of a Raspberry Pi?
Has anybody here an example for a lcd4linux.conf file, which makes use
of the Raspberry Pi GPIO pins?
Best Regards
Christian
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Prof. Dr. Christian Baun
2014-08-31 20:12:01 UTC
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Hi all,

It is also my experience that the GPIO pins of the Raspberry Pi are
very simple to access.

It is quite popular [1][2] to connect HD44780 compatible LCDs via
these GPIOs and access them via LCDproc [3]. The drawback (in my
opinion) of LCDproc is that the configuration is not very
user-friendly compared with LCD4Linux.

In the last hours I did some investigation about options to emulate
the parallel port via the GPIO pins of the Raspberry Pi. But up to now
I found no existing and promising solution.

Another option is to implement a LCD4Linux GPIO driver for the
Raspberry, but I think my skills in C are not good enough.

A the moment I think I will code a tiny script like this one [4] to
get the output I want.

Best Regards
Christian

[1] http://www.boeeerb.co.uk/pi-lcd/
[2] https://learn.adafruit.com/drive-a-16x2-lcd-directly-with-a-raspberry-pi/
[3] http://lcdproc.sourceforge.net/docs/current-user.html#hd44780-raspberrypi
[4] https://learn.adafruit.com/drive-a-16x2-lcd-directly-with-a-raspberry-pi/python-code
Post by Johan Swenker
Hi,
I would like to disagree. Even though lcd4linux is older then the raspberry,
the GPIO-pins of the raspberry are
as versatile as the parallel port of yesteryear.
Using a search engine you will find several people who have connected an LCD
https://learn.adafruit.com/downloads/pdf/drive-a-16x2-lcd-directly-with-a-raspberry-pi.pdf
They even have software, though incompatibel with lcd4linux.
The same search engine will also be able to find you several LCDs with an
I2C interface (implemented by
http://www.bitwizard.nl/wiki/index.php/SPI_LCD
Regards Johan
Post by Michael Reinelt
Hello Christian,
as lcd4linux is a lot older than raspberry, I don't think that it will
work, at least not out-of-the-box.
back in the "good old days" the only GPIO-like thing on a PC used to be
the parallel port, and thats what a low-level
driver exists for (drv_generic_parport), which uses either extremely old
school io instructions, or ppdev.
As I have absolutely no idea how GPIOs are controlled on a raspberyy, I
cannot advice you how to implement it.
maybe using some kind of i2c-to-parallel chip could work, too.
regards, Michael
Post by Prof. Dr. Christian Baun
Hi all,
is it possible to use LCD4Linux with a LCD (HD44780 compatible
controller), which is attached to the GPIO pins of a Raspberry Pi?
Has anybody here an example for a lcd4linux.conf file, which makes use
of the Raspberry Pi GPIO pins?
Best Regards
Christian
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Michael Reinelt
2014-09-03 12:08:30 UTC
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Post by Johan Swenker
Hi,
I would like to disagree. Even though lcd4linux is older then the raspberry, the GPIO-pins of the raspberry are
as versatile as the parallel port of yesteryear.
I fully agree. But lcd4linux (and the HD44780 driver) does not support driving a display with GPIO pins, because
yesteryear we did not have them.
Post by Johan Swenker
The same search engine will also be able to find you several LCDs with an I2C interface (implemented by
adding a microcontroller board to the LCD). Among them: http://www.bitwizard.nl/wiki/index.php/SPI_LCD
using kind of a converter (e.g. LCD2USB) would also be a proper solution.

I think the HD44780 driver supports i2c, too (but I'v enever used it)

regards, Michael
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http://home.pages.at/reinelt
GPG-Key 0xDF13BA50
ICQ #288386781
Luis Correia
2014-09-03 13:31:11 UTC
Permalink
Hi there,

as far as I can remember, the i2C driver adaptation that I've made to
hd44780 could be modified to work with raspi.

However, I know that the technique that I used at that time was very
bitbang intensive and not very useful I got CPU usage of over 40%, just for
lcd4linux.

It may be beneficial to write a new driver from scratch for the raspi but I
have no idea of the effort this would need.

Luis Correia

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