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little mistery on a hd44780 compatible LCD

Hi to all

At power up i am often stuck with black squares on a varitronix LCD display, that i use just for test in place of a Powertip LCD(that i have not in this moment). No software delay looks able to fix the problem.

touching the ENA pin(commonly pin 6),or connecting it to GND through 1 MOhm solves completely the problem Why? This pin is driven by the RA0 output of a PIC16f628 ,that being a CMOS output should not need any external pull up or pull down. The initialization is done following the sequence on data sheet,in 4 bit mode,and i write checkin the busy flag.

Thank you! Diego.

Reply to
blisca
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Probably you have left RA0 in its default analog mode. All PIC pins that have analog capabilities come up in analog mode, just because you might have an arbitrary voltage connected. Even though analog mode is usually not what you want.

In the case of the 16F628, it's the analog comparator. From some source of mine, I think you want:

movlw b'00000111' ; comparator off movwf CMCON

Other PIC chips will have other analog devices you will want to turn off if you're using all digital.

--
Ben Jackson AD7GD

http://www.ben.com/
Reply to
Ben Jackson

MOhm

I did it exactly in this way,but thanks

being the cable( about 3.1 inches long) the main difference with the original model i'm thinking to a ringing or something loike this,but sadly i dont have a digital scope in this moment

thanks again

Reply to
blisca

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