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LCD Interface

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Flipsyde412

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Is there any way an LCD display would work without using PIC. Just a logic gates approach. Can anyone give me a suggestion to this problem. I'm working to build a fuel dispenser prototype.So i guess it would be better to used an LCD rather than a 7-segment.
 
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i think it is mearly possible to do it with gates... and nobody on this forum would even attembt to do so... this would be really crazy!

i guess you'r new to micro controllers and hope to get away with a slightly more complicated gates array.. but not, you'll have to step into micro controllers.. and as gramo said, it is really easy, whether you'r using PIC or ATMEL..
 
Flipsyde412 said:
Is there any way an LCD display would work without using PIC. Just a logic gates approach. Can anyone give me a suggestion to this problem. I'm working to build a fuel dispenser prototype.So i guess it would be better to used an LCD rather than a 7-segment.
Contrary to popular belief it is actually quite easy to drive a direct drive LCD with logic. You do not mention how complicated the LCD is.

Any static drive LCD can be driven by taking the data from the 7 segment decoders through EXOR gates with the second input to and oscillator that also drives the LCD common pin.

Dan
 
I suppose most of us (myself included) immediately thought of LCD's with onboard controllers (like the HD44780) which we're used to using, rather than the much cheaper direct-drive LCD panels, which are in fact much better suited to logic control, as cadstarsucks pointed out...
 
hi,

The MM5453 LCD driver ic is able to drive four, 7 segment LCD's.

Its handy if you want to locate the display at some distance from the driving source, it just requires a 4 wire connection.

If you wanted to drive it without a PIC, its possible to use logic gates, shift registers and edge switches, but it is a real hassle.

Ideally a PIC is the best choice.

Attached diagram shows a general layout for the device.

EricG
 
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ericgibbs said:
hi,

The MM5453 LCD driver ic is able to drive four, 7 segment LCD's.

Its handy if you want to locate the display at some distance from the driving source, it just requires a 4 wire connection.

If you wanted to drive it without a PIC, its possible to use logic gates, shift registers and edge switches, but it is a real hassle.

Ideally a PIC is the best choice.

Attached diagram shows a general layout for the device.

EricG

As could any shift register and for less money...

Dan
 
hi Dan,

Problem is the back plane switching, with standard SR's when driving LCD's,

I have used 4 bit SR's with the True/Comp outputs driven by a BP osc.
A 4 digit display requires 7 i/cs, which is not really an option.

If 8 bit SR's were used, you would still require 4 SR's and the BP gating for each segment.

Regards
Eric
 
ericgibbs said:
hi Dan,

Problem is the back plane switching, with standard SR's when driving LCD's,

I have used 4 bit SR's with the True/Comp outputs driven by a BP osc.
A 4 digit display requires 7 i/cs, which is not really an option.

If 8 bit SR's were used, you would still require 4 SR's and the BP gating for each segment.

Regards
Eric
I am well aware of the BP issue having designed LCDs for production...the best solution would really be a PLD...2 pins for an RC osc, a shift clock input, a data input and as many outputs as you need.

Dan
 
hi Dan,

I am also aware of the use of PLD's, having run my own international electronics design and manufacturing company for the past 25 years.

The MM5453 device for driving a 4 digit 7 segment LCD's is far more cost effective than individual standard SR's, as you suggested.

If you dont' agree sit down and work out the 'total' cost of using SR's and support devices, as opposed to the cost of the MM5453.

Like you, I agree that the OP, wanting to do it with individual logic devices is not the way to go.

Nice exchanging idea's with you.

Regards
Eric
 
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