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As said, i hooked up an lcd bought several months ago (LCM1602A-NSW-BBW), and got it nearly working, apart from the fact that the text is VERY dim.
As said elsewhere in the forum, and in the LCD plug, i turned the pot to the left to have text appear:but as soon as something starts to appear, the pot stops turning...
Logic jumper is to 5v, and the light one is on +3, along with closed limiting resistor jumper.
Can you check visually whether there is perhaps a solder bridge around the trimpot? Also, the lower-left pin of the trimpot should be at 0V, and the lower-right pin at 5V, if you have a multi-meter to check.
It should definitely be possible to get a good contrast, but the pot does indeed haev to be turned almost completely to the right, I think.
Oh, and is the backlight turning on as you expect? WIthout BL, these LCDs can be quite hard to read.
To me it looks like there is no problem with soder joints. Here are some pictures:
this one to show you what very dim text means to me (actually on the photo it is more readable than with human eye): image #1
Here is a macro shot of the trimpot (hope the image quality is enough): image #2
Again the trimpot, this time from from above: image #3
As you see, the backlight works as expected, and since letters are there, I think there is no problem with backlighting nor with logic.
I have two of these lcd plugs, both bought from you early this year: both have the same result. DO you think it would be feasible to replace the trimpot? what are the specs of the signal on the contrast? From pcb traces it looks it's the third on the lcd connection... I also see the signal coming from the IC: maybe something related to IC configuration? Just guessing though, i'm not an expert...
Thanks for helping.
Wild stab in the dark here, is the LCD a 3.3v or a 5v one? JC was originally supplying 5v panels as 3.3v models were rare as hens teeth. From the part number I think that's a 5v and if the only power source you have is 3.3v the 5v panel is very very dim. That's why I use 4xAAA batteries in my gadget as the 4.8v from these rechargeables gives a usable contrast.
What voltage do you have on your P connection?
POWER: that was the point!
Since there is no 3V33 mention at the end of the product number, and since this units were bought logn before june, i'm supposing it's a 5V unit. And i jumpered the logic accordingly.
During my tests, the node was powered from USB, and i assumed i had 5V on the power pin: i was wrong, since i'm using a 3.3 ftdi cable, so the voltage was down to 3.3... hence all my problems.
When I hooked up the node to 3 AAA non rechargeable batteries, i finally got it working properly: image #4
That was a pretty stupid error: really thank you for helping me out.
Just a quick question on the necessity of a simple trick i found to get me going during the developmente/debug process: image #5
I took a 6 pin, male to female cable, and extracted from the male plug the cable that brings 3.3 volts from the FTDI pcb regulator to the jee node: i know that all the PWR pins are connected to each other, but i think this one should be an exception, since this one is already 3.3 volts, and i don't think this power line goeas through to jeenode voltage regulator: afaik it would simply not power anything, since the VR needs a little more than 3.3v to do its job.
Can i void this precaution, or did i thought it right?
Excellent, glad you got things going.
Nice mod with the cable too. I think it's a wise precaution to disconnect the 3.3v from the USB interface, otherwise the 4.5v from the AAs will be fed back up it.
The USB-BUB that JC supplies, and the TTL-R232-5V cable I use (from moderndevice), supply 5 volts to the PWR line on the FTDI connector, from here the VR produces the 3.3v the RFM12B and ATmega require. So having the onboard VR is very useful. You were unlucky in that you already had a 3.3v supply from your USB interface (I must admit I have never seen one of these).
I think the reason it was designed like this is that 99% of the people with previous ATmega experience are coming to the JeeNode from 5v boards, and therefore have 5v FTDI cables.
You could go one step further with your USB mod, find the 5v line on the mini-USB connection and connect that to your blue wire. Then you wouldn't required the battery when you were developing. The power connections are on the pins at each end. One side will be ground, the other 5v from the PC USB.
I bought the 3.3V FTDI breakout board from Sparkfun and on the power pin it's clealy written 3.3V since i was thinking that would be the only option with a jeenode working at this voltage.
From what you say, i understand that i could also use a 5V FTDI cable, but i did not go this way since i thought that the 5 volts logic on serial pins could damage the jeenode... is this the case?
Thanks again for your time.
The 5 volt FTDI logic levels are fine with the JeeNode. The ATmega328 used on JeeNodes is the same chip you'd fine on 5v Arduino boards, so 5v logic levels even with a 3.3v power aren't a problem for it.
I've got over a dozen ATmega328 chips on various JeeNodes, breadboards etc. Including the SMD variety, and I've programmed (and fiddle about with) every one with my 5v USB cable, believe me, they're fine.
Wonderful, that's great news for me, since I also have a 5V cable available.
I just tried it out and jeenode and lcd worked fine... no skmoke nor burned electronics smell too! Thanks, again!
I have yet to make any magic smoke escape from an ATmega, they are amazingly tough, even in the hands of someone as accident prone as myself!