Can't seem to get my LCD plug to work.

(13 posts) (4 voices)

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arnage

Hey there, first post on the board and I directly need help :/
Experience level: I have some basic Arduino knowledge and used rf12 modules before, but other then that no "jeestuff" specific experience.
I recently got two jeenodes and a LCD plug from the store. After assembly both jeenodes seem to work fine, but I'm having trouble with the LCD plug. (I got the one with a 2x16 screen included)
I soldered the jumpers as described on the lp1 page, connected it to a jeenode (tried both) and loaded the LCDdemo program but the LCD shows no signs of life at all. Here's a close-up of the lp1 board:
By manually connecting it, I was able to confirm that the backlight works, but I have not been able to get anything to show up on the screen nor can I get the backlight to turn on from a sketch.
Any advice on how to debug this further would be very welcome.

Posted 14/05/2010 13:03:53
jcw
Connections look good. Sounds like a software issue. You need to find out whether the plug is recognized - I assume you've doubled-checked the port number.
- if the light doesn't turn on, then the plug is probably not being found - if it does and nothing happens, check the contrast pot - it can be tricky to find the right level for visible characters
Try something like this to verify finding the I2C chip:
```
    PortI2C myBus (1);
    DeviceI2C myLCD (myBus, 0x24);
    ...
    if (myLCD.send()) Serial.println("found!");
```
Posted 14/05/2010 13:22:09


	
		
			
								
					arnage

				
			
			
				
You sure reply quick, thanks!
Just tried your verify code and the I2C chip is found, so that does not seem to be the problem.
Even though my backlight still does not go on, I also tried playing with the contrast pot, but I was not able to spot any kind of change on the display.
EDIT: Oops, I was to quick, some more twisting of the pot resulted in a "hello world!" so that's part one of the problem solved! Now I just need to find out why the backlight doesn't go on even though I confirmed that it isn't broken.



				Posted 14/05/2010 13:47:57
			
		
	
	
		
			
								
					arnage

				
			
			
				
As both the controller and the backlight by itself seem to work fine I suspected there might be a problem with the transistor. 
If I'm reading this correctly then the lower-right pin of the transistor should be connected to the ground, right? However between this pin and the ground pin on the header I measured a resistance in the Mega ohms.
What would be the best way to test if the transistor is working correctly?



				Posted 14/05/2010 22:20:09
			
		
	
	
		
			
								
					jcw

				
			
			
				
Sounds like a bad connection. Perhaps briefly touching the pin with the tip of a soldering iron will fix it?



				Posted 15/05/2010 13:12:00
			
		
	
	
		
			
								
					arnage

				
			
			
				
Good news, that was indeed the solution, a little bit of solder fixed it, Thanks again for the help.



				Posted 18/05/2010 06:44:45
			
		
	
	
		
			
								
					raalst

				
			
			
				
maybe a tip : the splendid photo on the first post would be a nice addition in the LCD hardware documentation.
As a true dutchman, I felt uncomfortable to start soldering and shorting things on my expensive (cough) new LCD board without such a picture.
as an aside : I got one female connector and two strips of 6 pins with the LCD. there is no picture (i have found) clearly showing how board and lcd are joined. I can use the two rows of 6 pins, but then the female header for connecting the plug does not make sense. it should be male to match the female plugs on the jeenode. besides I fear the twisted metal tabs of the lcd would cause a short on the plug because they would be so close. 
JC, can you show or tell me what is the intended use of those connectors and/or if I maybe lack one? 
Regards, 
Ronald



				Posted 19/05/2010 10:37:01
			
		
	
	
		
			
								
					jcw

				
			
			
				
Sorry - yes, I will. Quick answer for now: use leave the middle 4 pins unconnected, use the 2x 6 pins for the rest. The female header is probably part of the battery pack.



				Posted 19/05/2010 11:13:26
			
		
	
	
		
			
								
					raalst

				
			
			
				
no need for sorry, thanks for the clarification !



				Posted 19/05/2010 11:42:30
			
		
	
	
		
			
								
					epokh

				
			
			
				
Hello.
Same problem here, the LCD label says:
2010-2-2
LCM1602A-NSW-BBW
so I suppose it must be to be powered with 3.3.
so according to the blog I should jumper the LIGHT and LOGIC to HIGH and what about R3?
Should I put the current limiting resistor or jumper it?



				Posted 17/06/2010 19:26:27
			
		
	
	
		
			
								
					jcw

				
			
			
				
Can you help me figure out how to improve the wording of  ?
The way I read that, both jumpers go to +3V and the backlight resistor is optional, so a jumper instead is fine.



				Posted 17/06/2010 19:35:25
			
		
	
	
		
			
								
					epokh

				
			
			
				
But it is said:
>For the LCD from Jee Labs, use logic level set to PWR 
>or +3V (depending on which type of LCD you got, see below)
And that only the LCD with 33V33 suffix on the label both logic and power must use the +3, so I assumed that for the non 33V33 boards I need to shorten together the HIGH and middle pins.
It will be more easy to have a picture for the 2 types of configuration so that one does not get confused.



				Posted 17/06/2010 21:02:16
			
		
	
	
		
			
								
					jcw

				
			
			
				
Ah, ok, non-33v33 - yes, correct. I'll update the page. Pictures would be a good idea.



				Posted 18/06/2010 09:18:03