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HP Forum Archive 18

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Re: Phoenix 45s: 2 and 4-line displays
Message #1 Posted by Pavneet Arora on 10 Nov 2007, 10:31 p.m.

Thanks, Dave, for the clarification. I understand the design objectives a bit better now.

Backlighting for my work is still highly desirable since I am often in situations with low light, but if this doesn't have enough appeal to others I can live without it.

Cheers.

Edited: 10 Nov 2007, 10:32 p.m.

      
Re: Phoenix 45s: 2 and 4-line displays
Message #2 Posted by DaveJ on 11 Nov 2007, 1:37 a.m.,
in response to message #1 by Pavneet Arora

Quote:
Thanks, Dave, for the clarification. I understand the design objectives a bit better now.

Backlighting for my work is still highly desirable since I am often in situations with low light, but if this doesn't have enough appeal to others I can live without it.

I think the backlight camp would prefer a permanently luminous OLED display. In that respect a calc that offered either an LCD or OLED option without any changes has a lot going for it. But that's a 20x2 display only, unless someone can find a 4 line OLED screen display module. When designing a calc there are tradeoff's like this around every corner. Not one single person will ever be 100% pleased.

Dave.

            
Re: Phoenix 45s: 2 and 4-line displays
Message #3 Posted by Walter B on 15 Nov 2007, 2:14 a.m.,
in response to message #2 by DaveJ

In character/line-based LCDs I can't find a decent way to display even simple mode indicators (like Polar, Radians etc.) without losing a whole lot of space. IMHO this is another major drawback of all the LCDs presented here so far. If confirmed, this will force us to a full dot matrix or a custom display. Sounds complicated and/or expensive :(

                  
Re: Phoenix 45s: 2 and 4-line displays
Message #4 Posted by Garth Wilson on 15 Nov 2007, 2:28 a.m.,
in response to message #3 by Walter B

Walter, all the intelligent character LCDs have a way to make your own custom characters. If they can fit in the 5x8 or 5x7 matrix, you can get it in. I've used this feature to get up to three tiny characters in the space of one in a diagonal arrangement, make icons, and so on. Does that help?

                        
Re: Phoenix 45s: 2 and 4-line displays
Message #5 Posted by Walter B on 15 Nov 2007, 12:45 p.m.,
in response to message #4 by Garth Wilson

For example, I can display decently 4 lines plus some mode indicators with 120x50 pixels:

I used 1 line for a menu here.

Now try the same with a 5x8 character line LCD.

1st: Forget soft keys :(

2nd: You cannot display "RPN" or "ALG" or "RAD" etc. in a simple way the user can differentiate them as indicators :(

Or is there a way I don't see?

Edited: 15 Nov 2007, 2:35 p.m.

                              
Re: Phoenix 45s: 2 and 4-line displays
Message #6 Posted by Garth Wilson on 15 Nov 2007, 2:42 p.m.,
in response to message #5 by Walter B

Quote:
Now try the same with a 5x8 character line LCD. 1st: Forget soft keys :( 2nd: You cannot display "RPN" or "ALG" or "RAD" etc. in a simple way the user can differentiate them as indicators :( Or is there a way I don't see?
True, you cannot display a string with narrower letters that would require use of the non-existent pixels in the space separating tne 5x8 blocks; but you can make any combination of pixels within a 5x8 block, so for example making the angle sign you have right in the middle of the display in your picture is not a problem. You can have up to eight different custom character definitions at a time, as if they were ASCII 00-07, although of course it would not true ASCII. You can re-define them on the fly.

In a project I worked on years ago, I had 32 custom characters, but we never needed more than a few at a time, so it fit well within the limit of eight. 28 of the customs were two characters in one block and two of them were actually three, stacked: "VOR" and "TWR". (The "R" had to be "r" since that can be displayed in a 2x2-pixel space.) As you've probably guessed by now, it was for an aircraft application. Any of your custom characters can appear as many times in the display as you want, as long as there are not more than eight cutom definitions at once.

Some of the characters often used in math are already included in the standard character set, so they would not have to be custom-defined. The LCDs I've worked with all had the alpha, beta, sigma (both upper-and lower-case), ro, square-root symbol, degree symbol, "-1" and "x" raised as exponents, theta, infinity symbol, capital omega, lower-case mu, X-bar, divide symbol, pi, left and right arrows, and the raised logical-AND dot built in, plus a bunch of Japanese characters I have no use for.

Graphics would be pretty limited. Horizontal bar graphs work out well though. Since there's a pixel row missing between 5x8 blocks, what I've done is to only use columns 1, 3, and 5 in each block, so it looks like a string of vertical marks with space between them, instead of being solid black for the whole length of the bar. A 40-character line then gives 121 possible lengths (including length 0) for bars in a bar graph. More than one bar per line is possible too.

As for soft keys, there's nothing that says the labels have to be displayed in inverse video.

                                    
Re: Phoenix 45s: 2 and 4-line displays
Message #7 Posted by Walter B on 15 Nov 2007, 5:11 p.m.,
in response to message #6 by Garth Wilson

Quote:
As for soft keys, there's nothing that says the labels have to be displayed in inverse video.
How does this influence the width of a text? Please explain.

The point is: Assume you have a 20x4 line LCD, and you want to use the 6 keys right under the display for menu control, i.e. as soft keys. Then, 20 ENTER 6 / results in mere 3 letters per soft key. And there is no workaround :( , since, as you wrote,

Quote:
... you cannot display a string with narrower letters that would require use of the non-existent pixels in the space separating tne 5x8 blocks; but you can make any combination of pixels within a 5x8 block ...
Fully agree.

So, the basic questions are: Assume you have a line display; how do you tell the user the lowest line is containing soft key labels now? And what will change when it returns to being a "normal" output line?

                                          
Re: Phoenix 45s: 2 and 4-line displays
Message #8 Posted by Garth Wilson on 15 Nov 2007, 5:40 p.m.,
in response to message #7 by Walter B

I do like soft keys for certain things.

Quote:
So, the basic questions are: Assume you have a line display; how do you tell the user the lowest line is containing soft key labels now? And what will change when it returns to being a "normal" output line?
How about using a custom character (call it an icon if you wish) at each end of that line, to indicate that it is now a softkey label line? Or, to avoid losing the use of one character at each end, how about a custom character between softkey labels-- maybe a double-thick underscore?

I suppose you could go to the extreme of putting a mouse ball under the calculator and making a point-and-click interface; but it is my experience that limitations usually are not nearly as serious as perceived if you're creative and always ready to try a new approach instead of trying to force the design to mold around familiar ideas.

Edited: 15 Nov 2007, 5:41 p.m.

                              
Re: Phoenix 45s: 2 and 4-line displays
Message #9 Posted by reth on 15 Nov 2007, 10:55 p.m.,
in response to message #5 by Walter B

That display looks perfect in terms of character size and overall, unlike the 2*40 one ;)
Cheers,
reth

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