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Topic: Looking for the GLCDcmd Library for I2c Backpack (Read 1 time) previous topic - next topic

zyxel13

Hello,

some Years ago E.U.A released his GLCDcmd Library for using a I2C Backpack:
http://forum.arduino.cc/index.php/topic,37987.0.html

Unfortunately the Link to the Zipfile does not work anymore (too long ago)....

Perhaps somebody still have it, could you pls send it to me.

Thankyou in Advance,
Konstantin

bperrybap

I had a copy of it several years ago.
I was looking for it about a year ago but I couldn't find it.
I was hoping to find it and tweak it for openGLCD.

--- bill

david_prentice

Surely an I2C backpack will just transform your snappy graphic display into a slow motion device.

I presume that you are interested in the 8-bit PCF8574 adapters rather than a 16-bit I2C port expander.
You can drive a ST7920 via its 4-bit parallel interface with an I2C backpack just like a regular HD44780 character display.   

It is much simpler and faster to use its SPI interface for graphics.

You could use a 16-bit expander for a KS0108 or T6963C display.

David.

bperrybap

#3
Feb 21, 2016, 09:31 am Last Edit: Feb 21, 2016, 09:32 am by bperrybap
Surely an I2C backpack will just transform your snappy graphic display into a slow motion device.
Actually that was not the case for this library.
The interface used in that library was a message interface that pushed all the intelligence (rendering) to the slave device with the backpack.
So the master was sending very little information over the i2c interface.
And because of this, the avr on the master was free to do something else while the graphic operation was being done.
It was essentially a dual processor system with an i2c interface between them.
That is the value of having an intelligent message interface vs doing it by controlling the glcd pins over the i2c with an i/o expander. The i/o expander methodology is MUCH slower.

And because all the rendering and fonts lived on the slave, the code size on the master was smaller than when using the display directly attached.



--- bill

david_prentice

Ah-ha.    Using the I2C interface for high level commands is fine.     They get sent via interrupts anyway.   So you can get on with your own application.

Yes,  you can have a secondary AVR that receives commands via I2C and does the donkey work for the display.     As far as I know,    Digole use a PIC cpu for this purpose on their intelligent monochrome displays.    And can use UART, SPI or I2C for receiving the commands.

Several makes produce intelligent full colour TFT displays.

The PCF8574 backpacks are not intelligent but they are cheap.

I will have a look at the message link from the OP when I am at a PC.    Clickable links can be used by Tablet or PC.   

David.

Alvgon

I know ... I know ... is a very old post.

But GLCDcmd is just what I need for my project.

Has it been any type of change on current situation of GMCDcmd disapearance?

bperrybap, how about including it as an accessory to openGLCD ? (if you did find it, of course)


TIA

bperrybap

I have looked and looked and was never able to find it.
If someone has a pointer to it I would be glad to take a look at it and see what it would take to get it working with the latest openGLCD.

--- bill

Alvgon

Bill, as an alternative to GLCDcmd ... is it possible to modify openGLCD to free SDA and SCL pins?

I've wired my display and openGLCD test v1.03 is working flawlessly.
But I want to connect an RTC module, so I need A4 and A5 pins free.

Can I use, i.e. D2 and D3 in their place?

I'm afraid I'm not so knowledgeable to do that mod myself ...


TIA.

bperrybap

Bill, as an alternative to GLCDcmd ... is it possible to modify openGLCD to free SDA and SCL pins?

I've wired my display and openGLCD test v1.03 is working flawlessly.
But I want to connect an RTC module, so I need A4 and A5 pins free.

Can I use, i.e. D2 and D3 in their place?

Yes you can use any Arduino pin for any GLCD function.
See the included manual. It explains how to swap/change pins.
All you have to do is modify the pin configuration file for the board you are using.
It is described in the documentation.

--- bill

Alvgon

Bill, have you seen this ?

https://github.com/sparkfun/GraphicLCD_Serial_Backpack

It has the firmware for a MEGA168 ...

Is a bit too dense for my current C++ knowledge

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