13th March 2012 05:33 AM
problem with lcd
hi everyone. I got a lcd volt meter project from internet. my friend is doing that project. He has not
connected any inputs or anything but he is getting ouput at lcd as shown in pictureVOLT METER.jpg
I do not under stand what is the problem
I have also attached the necessary files as below
13th March 2012 11:12 AM
Appears to me like a timing issue.... I thought you had to specify Xtal speed.
13th March 2012 03:12 PM
It probably doesn't help having massively long leads to the display - however, it's the sort of 'wrong characters' you can get if two of the data lines are shorted together (or to ground), so it's worth checking carefully for shorts.
14th March 2012 12:12 PM
I told him to change the configuration of pic to RC oscillator and also changed the crystal to RC(R=3.3k and C=100pf) and now it displays correctly. Why is that?
14th March 2012 12:27 PM
Like I said... A timing issue.... A R/C configuration will be running considerably slower... The timings on the LCD are now WELL above the minimum settings..
I thought that you needed to specify a crystal frequency with that compiler (I may be wrong ).
14th March 2012 10:31 PM
The 44780 chipset needs a time delay inbetween writing characters, as the chip needs to update the display, if you try to write another character or certain instructions too soon after the last one then the display will corrupt, if you wait to long it will still work fine.
Your mates delay routine was probably not taking long enough as the xtal frequency wasnt setup correctly.
I assume that the software is using the minimum wiring communication protocol, if all the connections from the display were made available there is a busy flag that can be read before writing the next character.
Basically I've just expanded on the post above.
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