Author Topic: LCD HD44780 vs SPLC780D whats the difference? & good large LCD  (Read 26899 times)

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Offline cowboy303

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LCD HD44780 vs SPLC780D whats the difference? & good large LCD
« on: November 01, 2012, 01:21:09 am »
I working on a project and want a larger LCD to work with my Arduino.  Was looking on eBay and found one with the SPLC780D for $22 and from what I can see its the same as the HD44780. am I right?
Does anybody know of a good large LCD that has the  HD44780 or Equivalence?

Thanks for the help.
 

Offline mariush

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Re: LCD HD44780 vs SPLC780D whats the difference? & good large LCD
« Reply #1 on: November 01, 2012, 02:30:04 am »
Read this page:

http://en.wikipedia.org/wiki/Hitachi_HD44780_LCD_controller

See the Instruction Set? A lot of chips that are HD44780 clones have the same commands ... so if you look into lcd displays and you read the datasheet and find those instructions, it will be HD44780 compatible.

For example, go to digikey.com at LCD Displays Alphanumeric and Character:  http://www.digikey.com/product-search/en/optoelectronics/display-modules-lcd-oled-character-and-numeric/524437

Select Parallel interface because the HD44780 is working in either 4-bit or 8-bit mode, so using several lines in parallel from arduino.  (note here: There are some lcd displays that are serial, using just a couple of wires... which actually still use a hd44780 close and there's just a simple chip in between doing the serial to parallel conversion)

Now select the number of characters you want, for example 80, to get a 4 x 20 digit display.

Now go through each and read the datasheet - you'll find probably 90% of them have those instructions in the datasheet. That means they're compatible.

For example : http://www.digikey.com/product-detail/en/NHD-0420AZ-FL-YBW-33V3/NHD-0420AZ-FL-YBW-33V3-ND/2773600

It's a 3.3v 4x20 display ... datasheet says at page 2:

Functions and Features
•  4 lines x 20 characters
•  Built-in controllers (ST7066U)
•  +3.3V Power Supply
•  1/16 duty, 1/5 bias
•  RoHS compliant

and at page 5 you have a link to the full datasheet for that ST7066U which you'll find it has the same instructions as HD44780 ... at page 17 in that link.

and if you're still not sure, at page 6 you have the instructions, which are, again, the same as the ones for HD44780.

-=

Or let's take another example: http://www.digikey.com/product-detail/en/C-51847NFJ-SLW-ADN/73-1249-ND/769330

If you open the datasheet, you'll notice there's no command set in it, but if you look at page 10, you'll see in the diagram that all the pins go into a box that says "NT8331 or equivalent" - that's the chip on the lcd display.
So now you can search in google for "NT8331 datasheet" and you find the datasheet for it... I've put it here for your convenience : http://savedonthe.net/download/407/NT3881D.html

If you look in this datasheet at page 16, it's the same Instruction set... so this chip is also a clone of that Hitachi HD44780 ... bingo...


Pretty much all lcd displays that look like the one above, with 8 pins for data signals, are using those HD44780 clone chips. Some have the pins on the side, in a 2 x 8 layout, like this one : http://www.digikey.com/product-detail/en/NHD-0220FZ-FSW-GBW-P-33V3/NHD-0220FZ-FSW-GBW-P-33V3-ND/2773592  ... still the same clone chips..
« Last Edit: November 01, 2012, 02:31:35 am by mariush »
 

Offline cowboy303

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Re: LCD HD44780 vs SPLC780D whats the difference? & good large LCD
« Reply #2 on: November 01, 2012, 02:57:30 am »
Thank you so much!
 

Offline cowboy303

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Re: LCD HD44780 vs SPLC780D whats the difference? & good large LCD
« Reply #3 on: November 01, 2012, 03:43:40 am »
One more thing if you don't mind.
I found a different LCD that fits my needs and it's all the same as the HD44780 except it has 18 pins and instead of 16, and pins are labeled 17:NC/Vee,  18:NC.  what do those pins do?
 

Offline mariush

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Re: LCD HD44780 vs SPLC780D whats the difference? & good large LCD
« Reply #4 on: November 01, 2012, 04:58:41 am »
The datasheet usually says what they are for.

Usually, I think they are for the case when they implement RGB backlight.  The backlight is like accessories on cars, they make the same base model and the put either single color led backlight, or several lights.

Normally, you have GND and + backlight. When there are 18 pins, you have GND,  + red, + green, + blue.  Therefore, you can have whatever nuance of color you want.

For example, this would be RGB backlit: http://www.digikey.com/product-detail/en/NHD-0216K1Z-FS%28RGB%29-FBW-REV1/NHD-0216K1Z-FS%28RGB%29-FBW-REV1-ND/2172437

Datasheet says :

15  LED?  Power Supply  Ground for Backlight
16  LED?RED  Power Supply  Power supply for backlight (2.2V)
17  LED?GREEN  Power Supply  Power supply for backlight (3.3V)
18  LED?BLUE  Power Supply  Power supply for backlight (3.3V)

The voltages are just the V forward of the LEDs. It's just a question of selecting a proper resistor for each one to limit the current so that you won't burn them up ..

For example, if you power all three from 5v and you want to limit the leds to maximum 5mA for each one, you have the Ohm's law formula:  R = V/I  = (5v-2.2v) / 0.005 (mA is thousands of an A) = 560 ohm  for red ,  (5v-3.3v) / 0.005 = 340 ohm for green and blue ... so you'd round up to the standard 560ohm and 330 ohm resistors.

The datasheet says the leds support up to 20mA for each led, but that would be really bright.  If you play with the maximum current you allow for each led, you get different "strengths" of that color, so when they're combined you'll get a different color. Or you can simply not connect one of the colors and use just two or just one.



Or you can set the maximum current and change the level of strength of that color using PWM - sending power and stopping power and repeating at a frequency faster than what humans perceive, like how this guy does:



« Last Edit: November 01, 2012, 05:06:58 am by mariush »
 

Offline amyk

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Re: LCD HD44780 vs SPLC780D whats the difference? & good large LCD
« Reply #5 on: November 01, 2012, 04:13:27 pm »
One more thing if you don't mind.
I found a different LCD that fits my needs and it's all the same as the HD44780 except it has 18 pins and instead of 16, and pins are labeled 17:NC/Vee,  18:NC.  what do those pins do?
NC = No Connection, pin is electrically unused (or could be for test purposes); leave it isolated.

Vee for HD44780-based displays is usually the LCD drive voltage (referred to as bias); some models need negative Vee, some need positive Vee with respect to GND. Look at the datasheet for more information.
 

Offline Fusi

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Re: LCD HD44780 vs SPLC780D whats the difference? & good large LCD
« Reply #6 on: August 29, 2017, 02:12:44 pm »
Hi! A found a difference on timing characteristics, but not found anything on the datasheet. I use Arduino LiquidCrystal library for many HD44780 based LCD-s without problem. Now, with two SPLC780C based display i found instability with the lcd.createChar command. My charcters are displaying randomly confused after a powerup, and displaying good after another powerup. After increasing the delay times inside this function (in the LiquidCrystal.cpp file), the problem is solved.

void LiquidCrystal::pulseEnable(void) {
  digitalWrite(_enable_pin, LOW);
  delayMicroseconds(3);     //WAS 1
  digitalWrite(_enable_pin, HIGH);
  delayMicroseconds(3);    // enable pulse must be >450ns        //WAS 1
  digitalWrite(_enable_pin, LOW);
  delayMicroseconds(200);   // commands need > 37us to settle   //WAS 100
}

Save the library as SlowcheapLCD, and don't touch the original! :-)
 
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