128x64 Serial LCD won't display

Hi! I’m working with the Redboard from Sparkfun and their 128x64 serial LCD (https://www.sparkfun.com/products/9351) and I’m running into an issue.

I have tried several different example codes, and the display has not been working even though the backlight comes on when powered. Most recently, I tried running the SerialGraphicLCDDemo (see attached). As usual, when I first plug it into the Redboard, the backlight comes on. Once I upload the program, nothing happens for about 5-10 seconds, and then the backlight goes off and gradually comes back on again. After that, more nothing.

So, I am not sure what the problem is or how to go about fixing it. I’ve tried looking for some answers, but haven’t found anything useful. If someone has an idea, solution, or website with the answer I missed, that would be great!

SerialGraphicLCDDemo.ino (15.1 KB)

Just out of curiousity, do you have prior experience working with serial transmission in general ? Robert

Looks like the backlight demo is executed correctly. Possible problems: - Backpack is not connected correctly to the display (did you get it ready assembled?) - The display contrast is not correct. Infact i wonder where and how to change the contrast. I do not see the var pot on the sparcfun pictures. If you see a var pot somewhere try to change it during the demo execution.

Oliver

Hello! Could you post a picture of the LCD, Fully connected and turned on? That could give us more information on what is wrong, and how to fix it!

Kind regards, -Goldfile

Robert - This is actually my first time working with serial transmission.

Oliver - I think you are right about the backlight demo working. I got LCD with the backpack pre-assembled from Sparkfun. And there is a var pot on the back of the backpack which I’ve tried playing around with, and it doesn’t seem to change anything.

Goldfile - I attached a picture of the LCD when it’s hooked up and on. Hopefully you can see that the backlight is on, but there is nothing displayed on the LCD.

I have the V_in and GND on the LCD connected to the V_in and GND on the arduino, and I have the RX of the LCD connected to digital pin 3 on the arduino. I tried running the code with the RX connected to TX (as it says to do in the code), but then the backlight demo wouldn’t even work. I found on some forum to try hooking it up to digital pin 3, and that’s when the backlight demo started working.

The redboard is a sparkfun UNO clone ? Have you tested it with a blink led example ?

And there is a var pot on the back of the backpack which I’ve tried playing around with, and it doesn’t seem to change anything.

If everything is powered, then you should see the pixels of the display of the var pot is at one of the extreme positions. It might be required that you see from the side to the display (not from the top), If you really do not see anything, then i would assume, that the negative voltage is not working.

Oliver

Robert - I have not tested the Redboard with the blinking LED example, but I have gotten it to work with a basic, non-serial, 16x2 LCD (https://www.sparkfun.com/products/255)

Oliver - What would it mean if the negative voltage were not working, and is there a way I could fix that?

Oliver - What would it mean if the negative voltage were not working, and is there a way I could fix that?

LCDs require some strange extra voltage. If this is not available, you can not see any pixel. I have never seen a damaged voltage converter, but it might be possible. Maybe you have some wiring error.

Oliver

Do you have a multimeter you can use to measure the voltages on the Rx & Tx pins of the lcd ? Do you have the Tx pin connected as well (even though it probably does not send anything) ? What baud rate is it running at ?

Can 128X64 LCD work with arduino without using any additional IC or driver circuit??

shivam_savs: Can 128X64 LCD work with arduino without using any additional IC or driver circuit??

The answer is "Yes".

But i assume your question is more like this: Which 128x64 LCD works with Arduino Uno? Answer: Usually ST7920 and KS0108 based LCDs will work without additional IC or driver circuit. T6963 based LCDs do not need a level translation, but might require a voltage converter.

Oliver

I have the V_in and GND on the LCD connected to the V_in and GND on the arduino,

You need to clarify this statement. The arduino has a "V in which is an unregulated input for the onboard regulator, and a +5V pin. It's possible the display has the same arrangement. We need to know if you are connecting two unregulated inputs to some power supply and if so what is the voltage of the PS. If you mean to say Vcc of the Display instead of V in, then we need to know what is the correct voltage for the display Vcc . Is it 3.3V or 5V ? If you mean you are connecting the Vcc of the display to the +5V of the arduino, then you need to state that. Please clarify. What are the voltages involved and are the Vin pins or Vcc pins ? Did you try the tutorial on this page ? https://learn.sparkfun.com/tutorials/serial-graphic-lcd-hookup/backpack-overview It says the display backpack can take up to 7V dc. So what voltage are you using on that pin ?

Voltages of up to 7V may be used to power the backpack, however, care should be taken to reduce the backlight duty cycle in such cases to reduce the chance of overloading the voltage regulator on the backpack. To avoid complication with the voltage regulator, it’s best to power the backpack at 6V. You can also get away with powering the backpack from another 5V source. Keep in mind that anything below 5V will result in issues with the backlight and/or the display. If you are powering the backpack from a computer USB port or a microcontroller, make sure the output is actually 5V and not something like 4.5V.

Did you read the "Serial Graphic LCD Hookup" tutorial ?

All commands are preceded with “|”, or ASCII decimal 124 (0x7C). This tells the display that a command sequence follows. Before any of the following commands are given, they must be preceded with “|”. The actual character “|” is not (and cannot) be printed to the screen.

LCD that I am using is KS0108, can you please help me with the connections of KS0108 LCD with arduino? I seached on the net and couldn’t find any appropriate video or tutorial.

shivam_savs: LCD that I am using is KS0108, can you please help me with the connections of KS0108 LCD with arduino? I seached on the net and couldn't find any appropriate video or tutorial.

Start a new thread for your questions, since this is unrelated to the original thread topic. But to get you going start here: google these: "arduino ks0108" "openGLCD" "u8glib"

--- bill