NOKIA LCD

[camp david]

Hello
I had complete a project of writing text on lcd Nokia 1100 with pic16f677
finishing programming the pic with no errors, however when I run the circuit
the text appears pale and it's difficult to be seen, sometimes when switch the circuit on/off many times it works fine ! I did the following to correct it
1. use condensers, at 7805 in & out pins, also in the 3.7v Z-diode.
2. change the setting of CCS, project oscillator, (xt, intosc,...)
3. change the frequency
4. turn all pins of 16f677 to be output

but no use, I really confused, any advices ?

[temtronic]

first thing that comes to mind....

1) are you runnig the PIC and LCD at 3.6 volts?
if not, then do so, as you CANNOT run the PIC at 5V and the LCD at 3v6.

2) PIC clock at 3v6 can only be 10MHz or less so you CANNOT run at 12, 16 or 20MHz.

3) Power supply cannot supply enough current. I'd think you need at least a solid 1Amp or more. Typically that means a 4700mfd cap on the raw DC, 1000 mfd on the 5V side with reverse polarity diode across Vin, Vout of 7805.


Since it 'kinda works' and 'appears dim', I think #3 is the problem.

hth
Jay

[camp david]

as you can see my first post , I used 7805 for pic , separated 3.6 using Z diode
.
the volts is well filtered , and I measured them during work , it's 5.2 v & 3.7 v
. I think the problem in the PIC already , because now , it's even not detected by the programmer,however it still runs the lcd with pale color , also when set it in the programmer it's itself not detected by the program , while another PIC is ok

[Ttelmah]

#1 in Temtronics reply. This is what you are doing, and risks damaging either the PIC, or the LCD, or both....

It's a bit like taking an industrial motor that runs off 110v power, and connecting it to a domestic supply at 230v, and then being surprised it doesn't work.

[camp david]

OK but the volts I have measured is reasonable
which one of them is wrong ?

[temtronic]

Query?
Are you powering the PIC with 5 VOLTS ??

Jay

[camp david]

Jay ?
whats wrong, is everything alright ?
.
is it the first time you work with PIC MCU
.
look at this

[temtronic]

Been PICking since '84, probably before you were born..Had CCS C compiler since PCM v2.453. Ah the good old days of UV eraseable PICs!

As I posted earlier you CANNOT run the PIC at 5 Volts with the LCD at 3v6. They will NOT 'like' each other and damage will occour.

That PIC will run at 3v6 so power it from the SAME supply as the LCD, then your project might work fine,providing PIC clock <=10 Mhz.

If you post a schematic of your project we can see what you're really doing.

Jay

[camp david]

Many younger kids more focusing and very well done the works
than elders ,for sure I just started the work with mcu's PIC since less than 6 months
you probably work since 80's , but you post as a newbie
if you just tell me that from the beginning instead of looping that way
regards Mr KING

[oxo]

What they are trying to tell you is that a 5V PIC will have 5v output signals. Putting these into the Nokia LCD which is powered at 3.6 volts will likely damage either or both of the PIC and LCD.

At the very least, the 5v signals will pull up the power to the LCD and cause the display to render strangely.

What you need is some level shifters, or get a 3.6v PIC!

[temtronic]

Actually it's far easier to do, simply connect the PIC to the 3v6 supply. As long as he runs the PIC at 10MHz or less, it will work fine. There's no need to logic level translation ICs and complicated wiring or PCB layout.
Maybe it's a language issue so I don't know how else to say that you cannot run the PIC at 5 volts and simply connect to a 3 volt LCD. It will never work properly and will damage the LCD.

I downloaded the datasheet for that PIC and it will run fine on 3v6.That's shown in the section titled 'electrical characteristics'. There's a chart that shows valid combinations of Vdd vs Xtal frequency. while you cannot run the PIC at 20MHz at 3v6, it runs fine at 10MHz. I've got some 16F886 running on 3v6, 10MHz with similar LCD modules and other 3v peripherals so I know what the book says it valid.

Jay

[kWoody_uk]

To be honest Jay, I'm surprised you even bothered to reply after the impudent remarks the poster wrote.

"Many younger kids more focused?" Not to my knowledge. Most of the young people I know spend most of their time on their phone. Go back before the days of internet and then see how he would have gotten something working without asking for help.

Cheek!

[camp david]

Sure , in logic 0=0 v & 1=supply voltage
I missed the difference between lcd & pic voltages
and I depended on the circuit I have built in Proteus
I will give it a try then back .

[camp david]

[temtronic]

You should read PIC101 sticky,then you'll know why none of the 'regulars' here usually help with 'Proteus problems'. Proteus is a very ,very poor excuse for a PIC simulator. EVERY schematic presented here in the past 5-8 years has been WRONG yet posters think 'well Proteus says it works, so it will work with real hardware'. NOT so.
I've got over 40 years in the design/build of microcomputer products and have never found a 'simulator' that properly,100% 'works' as in real life.never. I don't use them, tried and they ALL fail, so I use real hardware and test in the real world. Maybe that's not the 'way' it's done today, but it's worked for me and allowed me to retire when I was 35.
As you've found out you cannot directly wire a 5 volt PIC to a 3 volt LCD module. This SHOULD have been demonstrated in class on day 2 or 3 of 'Microcomputer101'. All it takes is 15 minutes of reading the datasheets of the devices and seeing that a logic '1' from a 3 volt device will NEVER be a logic '1' into a 5 volt device, and going the other way, well, POOF, there goes the 3v device(and your $$ !).

hth
Jay