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LED Strobe Project Oct 2010

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Watchdogdave_squibb21/04/11  08:49 am
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rich13
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Posted on Sunday, 17 April, 2011 - 01:38 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Hello

LED Strobe/Tachometer, Oct 2010

In my last post, i asked for help with the help for programming the 16f88 micro for this project.
It was my setup at fault and a duff chip,programming is back on. However, i apologise for asking again about this project, but ive a dellema with the LCD.

As i didnt have the correct LCD module as described in the project text, i had at hand from RS a new module;reference DisplayTech 162B. They provided the data sheet and i correctly established each pin and wired to the PCB*. All the unused pins(5,7,9,10,11)} on LCD as per project diagram gounded.
*(PCB from EPE PCB service)

LCD datasheet DisplayTech 162B :
http://ptm2.cc.utu.fi/~ptmusta/kuvat/elektroniikka/LCD/162b-.pdf

Powered up, and all was good, LCD was lit but only got the square 'bars' across the display.

I checked and triple checked the pin configuration for the module and the pin reference to the PCB,and usual checks for solder ect. Ive also programmed the chip numerous times,(and using a fresh chip). Programmer was a Willem.
Using code: ledstrobe-0410808A.hex from libary
Also tried code fom November folder for the LED strobe.

Assuming ive correctly flashed and assigned the pins corectly, is there anyone who has built the project or to advise on what cause i cannot get the correct display output. I dont want to abandon this project,ive put to much time into it and its a simple setup as it is.


Thanks in advance


Rich

(Message edited by rich13 on 17 April, 2011)
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muskrat
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Post Number: 364
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Posted on Sunday, 17 April, 2011 - 07:37 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

First, make sure the contrast control is working. It may be too high, causing the black squares.

The fact that you have the black cells is actually a good sign! Things are almost working.

There could be a timing problem, requiring you to delve into the source code to adjust it. Carefully compare timings in the datasheets between the original LCD and the one you have.
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cjaysharp
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Posted on Sunday, 17 April, 2011 - 08:20 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

If you've really grounded pin 5 I suspect that might be part of your problem, it's the contrast pin, different LCD modules require different voltages on that pin (some extended temperature modules and some old ones can require a negative voltage!) so I'm with Muskrat, I suspect that the contrast is wrong, a full row (or two) of black squares means the LCD is probably initialised but needs the contrast adjusting.
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cjaysharp
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Posted on Sunday, 17 April, 2011 - 12:17 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

It's been nagging at me since I posted my first reply, pin 5 is not contrast on a normal 44780 LCD, it's R/W.

I suggest you have a good read of that data sheet, pins 1 and 2 on your display are for the backlight so all other pins are +2, re-check your wiring.
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joe
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Posted on Sunday, 17 April, 2011 - 12:46 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

As cjay says, check your pin connections to the display VERY carfully.

Some LCD's pin numbering is completly nuts and don't assume that the pins run in order from 1 to 16 or whatever.

PC-1602-F

The image above is for a Powertip PC 1602-F display; looks like pins 15/16 were an after-thought but they put them at the start of the run and not the end.

Check the datasheet for the LCD you were supposed to have used and your actual one side by side; check the function of each pin and the pin position on the LCD module to make sure you really do have the correct wireing.

Joe
Read my ramblings - www.techbites.com/joe-farr
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farnsworth
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Posted on Monday, 18 April, 2011 - 09:42 am:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

This may or may not be relevant:

Iíve recently used an FECC1602B lcd display that has an auto-initialisation feature. There seemed to be contention between this and the typical initialisation routine included in various PIC projects. I found the best way was to wait 15mS after powering up to allow the display to initialise itself, and then issue instructions to change the settings as required. The unit initialises to 8-bit mode: if you want 4-bit mode you may need to send the Function Set command twice (the first can only be guaranteed to set 4-bit mode, not the display characteristics as well).
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rich13
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Posted on Wednesday, 20 April, 2011 - 09:54 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Apologies for not returning post, ive just got back from a few days away.

Thank you to all the suggestions, i did quickly power up and changed the contrast control as Muskrat suggested,but nothing happened, but i keep returning to cjsharp post, so when ive time, ill look at the datasheet again and check again the pinouts.

If you dont mind me posting back when ive tested ect.}

Thanks again

Rich
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muskrat
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Posted on Thursday, 21 April, 2011 - 04:24 pm:   Edit Post Delete Post Print Post    Move Post (Moderator/Admin Only)

Let us know what you find. It's always interesting and potentially useful to all of us.

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