Question

Hy, guys,

I am using the PmodCLS, and although it is retired now (October 2018), my project is ongoing with 4 of them, using an adapted VHDL demo code from resource center.

I am in need of using one 20x4 LCD module instead of the 16x2 I have there. 

As a first innocent try, I just connected in parallel the 20x4 pins with the 16x2 pins. The 16x2 continue to work, but the 20x4 shows only squares...(contrast and backlight connections are ok).

In the demo lookup file it does not seems to have a configuration command for the LCD. Is PmodCLS automatically configured for 16x2?

How could I use a 20x4 LCD on PmodCLS?

Does anyone have the information about the instructions set of PmodCLS that could be used on a 20x4 LCD?

Thanks for your help,

Guacamoleroger

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Hi @Guacamoleroger,

When you say a "20x4" do you mean displaying 20 characters horizontally and 4 characters vertically? I took a look at the datasheet for the LCD screen (available here) and the only options for the display is using a single line of 5x8 dot patterns, a single line of a 5x10 dot patterns, and two lines of 5x8 dot patterns, so my understanding is that the LCD screen simply does not support the 20x4 variant that you are hoping to use. Instead, the most you get is 16 characters in total, 8 for both lines.

Thanks,
JColvin

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Hi, JColvin,

Thanks for your return !

I am still working on this issue.

Sorry if I was not clear. You know, digilent display has 16 characters on each of its 2 lines. I have a 20 characters on 4 lines display. It is not related with the pixel x pixel char formation.

My main question is: If I disconnect the 16x2 LCD from the main PmodCLS board and connect the 20x4, does the software on PIC will display correctly? 

I noticed that the instruction set of PmodCLS could be set to (5B 5B)1h (set display mode, 0 = wrap line at 16 character, 1 = wrap line at 40 characters).  The HD44780 supports 20 chars on two lines (total 40 chars). But it is not sequential. The 17th char appears on the 3rd line and the 41th char appears on 4th line.  Does this 40 chars means (probably) two "lines" of 20 chars?

Regards,

Guacamoleroger

 

20x4.png

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Hi @Guacamoleroger,

Yes, I believe that would be the case with the 40 characters implying two lines of 20 characters for the HD44780 unfortunately. It looks like from it's datasheet, when you are using a longer display setting, it presumes you are using an extension driver of some kind to make the two existing lines longer.

With that in mind, I do not think there is a way to support a 4 line display with the available code for the Pmod CLS as the libraries are specifically tailored towards the HD44780 which does inherently does not support a 4-line display.

Thanks,
JColvin

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Hi JColvin,

Thanks for your promptly reply and explanations.

I would like to present here the suggestions to Digilent to offer a 20x4 display and a 8-bits serial to parallel SPI board. Although we have so many fancy high-resolution, touch-screens displays available nowadays, for a first step on a product development or simple applications, this kind of LCD module is still useful.

Thank you again,

Guacamoleroger

 

 

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