Maybe you should divide your tasks over multiple Arduino's

Actually he should consider multiplexing, so the LEDs and Multiplexing section of the forum would then be a more appropriate place to continue.

Hopefully Nick can combine these cross posts.

Don

But connecting the arduino ground the bread board ground works.

The signals from your Arduino to your LCD module need a return path back to the Arduino and that path is provided by the 'GND' pin.  The same GND pin is used for all of the signals and also for the DC power if you use the Arduino to power the LCD.

Don

An I2C 1602 LCD might be better (working with any system with I2C) and costs less than $15.

True, but only after you sort out which particular device you have.  Specifically what the I2C address actually is and which I2C chip pins match up with which LCD pins.  None of this is standardized and if you don't think this is a problem for beginners then you haven't been following this forum too closely lately!

Don

But was wondering would I be able to set this up as per the usual tutorial for arduino LCD's?
I guess Imm just worried as I would like to use the arduino LCD library, and it says the library is for use with screens using an "Hitachi HD44780 driver"
and I can't seem to find whether this has one or not??

That display should work with the LiquidCrystal library (any of them) without any problems.

DOn

With a 10k VR wiper connected to the V0 pin, I've tried connecting the other VR pins to: VSS/VDD, VDD/VOUT, neither combination worked.

My guess is that you need the other possibility for the two ends of the potentiometer, V_SS and V_OUT.

Don

You have to do the best with the information that you are given.

Don

I have a qy-2004A LCD by Parallax. I see some parallax LCDs work with the Arduino, but I can't get this one to work...

You have probably done something wrong.

Don

When you have trouble initially getting an LCD working, using either the default parallel connection or a serial interface, it is always a good idea to work with a static example.  This means doing your initial work solely in setup() and doing nothing in loop().  Right now you are aiming at a moving target which isn't a good idea for beginners.

Don

The variable resistor you mention is really a potentiometer which functions as an adjustable 'voltage divider' to provide the required level at pin 3.

For most displays this required level is around 0.5 volts but some displays work acceptably with 0v.  This means that you can start by connecting pin 3 to GND and see what happens.

Otherwise you will need two fixed resistors, a small one (around 1K) between pin 3 and GND and a larger one (around 10K) between pin 3 and Vcc. 

Don

You can adjust the contrast of the LCD display itself by replacing the potentiometer that is feeding pin 3 with a PWM signal.

You can adjust the brightness of the backlight by feeding a PWM signal to an appropriate transistor in the backlight anode or cathode lead (pin 15 or 16).

I have personally done neither so I can't help you with the code.

Don

Only top row blocks are visible.

Your LCD controller is not being initialized properly, possibly because of the pull-up resistor issue.

Do i need to you some resistors, to connect arduino with I2C-LCD?

The two I2C signal lines (SDA and SCL) require pull-up resistors.  If they are not provided on the pc board you will have to wire them up yourself.  If they are provided on the pc board you may still have to use some jumpers to actually connect them.

The reason they are not always provided, and the reason that they may not be connected even if they are provided, is because you only want to have one resistor connected between each line and Vcc regardless of how many I2C devices you are using.

As much as i know from documentation, i don't need to.

What documentation?

Don

Are these two programs supposed to be functionally equivalent or is the second one just a 'proof of concept'?

If they are supposed to be functionally equivalent then I think you have gotten a bit more minimal than you should have in your second version.

If the second program is just 'proof of concept' then you might start out by minimizing the original program first (to do only what you expect the second program to do) and then converting the new version of the original program to use hardware SPI.

I haven't used SPI recently and when I did it was on a different processor, but with a casual look at your code it seems that you will basically be substituting sendData() for LcdWrite().  This won't save much code although it will offload some work from the processor to the Serial subsystem.

Don

There should be no problem with the LCD itself (pins 1-14).  There could possibly be a problem with the backlight control since the backlight (pins 15 and 16 on most, pins 15 - 18 on the RGB) is not part of the LCD specification and they may not be wired similarly.  

Don

Edit: I do not have Eagle installed on my computer and Adafruit's schematic is in Eagle format.  If you can come up with a PDF version I'll see if I can determine how versatile the backlight wiring may be.

I'm glad that got you going.  You will probably get a nicer display if you can connect a potentiometer and adjust the voltage on pin 3.  Typically something around 0.5 volts gives the best results.

Don

I did not use the contrast ajust. The lcd isn't displaying
anything, just the backlight. Here is the datasheet:
http://www.farnell.com/datasheets/1485438.pdf

Anyone knows how to fix this?

The contrast adjustment connection (LCD pin 3) is not optional.

Your display might work adequately with that pin connected to GND but the display will most likely be blank with the pin left open.

Don