LCD character size

On Saturday, March 5, 2022 at 10:17:11 PM UTC, Rich S wrote:
> On Saturday, March 5, 2022 at 10:04:20 PM UTC, Rich S wrote: 
> > On Saturday, March 5, 2022 at 9:52:58 PM UTC, Rich S wrote: 
> > > On Saturday, March 5, 2022 at 9:25:11 PM UTC, whit3rd wrote: 
> > > > On Saturday, March 5, 2022 at 11:25:51 AM UTC-8, jla...@highlandsniptechnology.com wrote: 
> > > > > We're designing a new rackmount box, basicly a fancy power supply, 
> > > > > with an 800x480 4.3" LCD on the front. Roughly this: 
> > > > > 
> > > > > https://www.dropbox.com/s/8ubv5if7cbnsjzn/P940-8_front.jpg?raw=1 
> > > > > 
> > > > > Does anyone have an estimate of how many characters X and Y we might 
> > > > > use? 
> > > short answer: 
> > > get a Snellen Eye chart; Your characters size should be 
> > > at least as those at the 20:20 (6:6 in EU) line 
> > > For easy readability use double that (20:40) 
> > > 
> > > longer answer: 
> > > The characters need to be large enough to be distinguishable 
> > > from one another, from a stated maximum viewing distance, by 
> > > your intended user. 
> > > First I assume 
> > > your letters & numbers use a simple block type font (sans serif). 
> > > characters are high contrast (black on white background, or vice versa). 
> > > that white part of the image luminance is a comfortable brightness range. 
> > > the pixels constructing the characters are small, not visible at the viewing distance. 
> > > the person has with 20:20 vision (6:6 in EU). 
> > > (Apply formula here - to lazy to look it up) 
> > > 
> > > To the degree you vary from these assumptions, the size should be 
> > > increased. 
> > w = 2 * d * tan (2.5 arcmin) 
> > 
> > so if d = 6 feet = 72 in., then w = 0.0175" 
> > 
> > formula from here 
> > https://en.wikipedia.org/wiki/Snellen_chart
> This is the minimum "feature" size - i.e., the pixel, 
> your characters should be composed of. 
> Your 800x480 4.3"-diagonal LCD has dimensions 
> 5.375" x 3.225" 
> and a pixel spacing (assuming square pixels) 
> 0.00671875" 
> 
> So this is below w (above) 
> the pixels will not be visible at 6 ft.
the pixels will just become detectable at
0.00671875 / (2 * tan(2.5 arcmin)) 
= 27.7" = 2.3 ft.

Viewing closer than 2 feet, the pixellation
may not be a problem if your characters
are not too coarse, e.g., at least 12 x 12
pixels.

On Sat, 5 Mar 2022 13:25:04 -0800 (PST), whit3rd <whit3rd@gmail.com>
wrote:

>On Saturday, March 5, 2022 at 11:25:51 AM UTC-8, jla...@highlandsniptechnology.com wrote:
>> We're designing a new rackmount box, basicly a fancy power supply, 
>> with an 800x480 4.3" LCD on the front. Roughly this: 
>> 
>> https://www.dropbox.com/s/8ubv5if7cbnsjzn/P940-8_front.jpg?raw=1 
>> 
>> Does anyone have an estimate of how many characters X and Y we might 
>> use?
>
>Well, ten characters per inch and five lines per vertical inch is readable.   Typewriter spacing...
>
>More to the point, why do a new screen and protocol for a new box?  Could you go to USB or
>Bluetooth for the communication, and source a display (like a tablet, or electronic picture frame,
>or just an app for a cellphone) that has builtin software support?  

Good suggestion. We could duct-tape a cell phone to the back of the
panel.



-- 

I yam what I yam - Popeye

On 3/5/2022 2:25 PM, whit3rd wrote:
> Well, ten characters per inch and five lines per vertical inch is readable.   Typewriter spacing...

 From what distance?  I.e., when you put a display ON a bit of kit,
you are essentially defining how/where you expect the user to
interact with it.  If the user has other ideas, he's SoL (or,
your sale is lost to a competitor that accommodates his needs).

> More to the point, why do a new screen and protocol for a new box?  Could you go to USB or
> Bluetooth for the communication, and source a display (like a tablet, or electronic picture frame,
> or just an app for a cellphone) that has builtin software support?

Unless you are painting on a predefined "virtual display", you're going to
end up designing some display software.

Increasingly (almost to the point of being ubiquitous), devices are
shedding *their* displays in favor of some "remote" display/control
capability.  Devices look, more and more, like client (or, servers
if you're uncomfortable with the display-as-server model).

I.e., you expose the interface to the "back end".  This leaves you with
the task of designing a server that can harvest the information desired
and present it on *it's* UI.

And, if you stop thinking like an equipment manufacturer but, instead,
see your role in a *system*, then you can imagine the UI might NOT
want to conform to your idea of what the user *might* want to see
on a screen and, instead, let the user *build* an interface that suits
his needs.

Possibly simultaneously displaying information from other devices
(of which you may be ignorant!).

Isn't it annoying to have to deal with a variety of devices, each with
their own notion of *how* you should interact with them?

[Do you display the time-of-day?  date?  what timezone?  what format?
etc.  Do you really want to be making that decision for the user and
annoying him at your lack of foresight for *his* needs?  "Why are
the timestamps on your device skewed with respect to those on this
other device?"]

When I designed the UI for my disk sanitizer, I initially tried to
cram as much information on a "standard" display as possible.  So,
an "operator" could look at the state of all 60 disks at once in
order to get an idea as to their progress, completion times, failure
rates, etc.

But, there are countless collections of data that might be of interest;
what if the Operator wanted to focus on a *single* disk?  What if he
wanted to see it's historical performance depicted graphically instead
of a "current state"?  What if he wanted to *compare* two disks to
highlight differences?  What if he has a second such system -- another
60 spindles -- that he wants to monitor from the same point?  What
if that point is his *home* (cuz he doesn't want to sit around for
13 hours waiting for the process to play out)?  etc.

So, the smart solution is to separate the display from the device and,
once that connection has been abstracted/virtualized, spend effort on
ADDING VALUE to the UI beyond what you *thought* was appropriate.

> Doesn't it make more sense to use a mass-produced  standard software target instead
> of a novel build-from-sticks hardware assembly?

86 the hardware as you can buy something COTS for less dollars.

But, the software will likely still remain.  If you plan well,
you can write it portably to address a variety of likely
"presentation devices" -- just like web pages that display on
tablets, phones, PCs, etc.

The effort can then be leveraged, going forward, for other devices you
produce.

On Saturday, March 5, 2022 at 3:30:14 PM UTC-5, Jan Panteltje wrote:
> On a sunny day (Sat, 05 Mar 2022 11:25:36 -0800) it happened 
> jla...@highlandsniptechnology.com wrote in 
> <4cd72hleqqcmvfjmk...@4ax.com>:
> >We're designing a new rackmount box, basicly a fancy power supply, 
> >with an 800x480 4.3" LCD on the front. Roughly this: 
> > 
> >https://www.dropbox.com/s/8ubv5if7cbnsjzn/P940-8_front.jpg?raw=1 
> > 
> >Does anyone have an estimate of how many characters X and Y we might 
> >use? We'll try to fire it up next week and experiment, but I'd like to 
> >start thinking about screen layouts and have no idea about what might 
> >be reasonable. We'd want good visibility so wouldn't want anything 
> >really tiny. 
> > 
> >I'd prefer a fixed-size, fixed-pitch font, to keep the design simple. 
> >We might have some characters/boxes with different background colors. 
> > 
> >The off-screen (mechanical) pushbuttons will be page left/right and 
> >cursor up/dn/left/right, and a spinner knob. There will be some box 
> >overhead pages and one page per plugin board.
> If you do not need graphics then that resolution is probably overkill 
> 
> 128x64 LCD: 
> http://panteltje.com/pub/gamma_soectrometer_IMG_4505.JPG 
> 
> 640x480 same font... 
> http://panteltje.com/pub/xvtx-p.gif 
> 
> Make a drawing to size first? 
> 
> There are a million fonts to chose from, some are free. 
> Some LCDs have their own character set. 
> Does it run an OS? Linux Xwindows has many fonts

You are going to hate life when you develop presbyopia.  

-- 

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209 

On 3/5/2022 2:44 PM, Mike Monett wrote:
> whit3rd <whit3rd@gmail.com> wrote:
> 
>> On Saturday, March 5, 2022 at 11:25:51 AM UTC-8,
>> jla...@highlandsniptechnology.com wrote:
>>> We're designing a new rackmount box, basicly a fancy power supply,
>>> with an 800x480 4.3" LCD on the front. Roughly this:
>>>
>>> https://www.dropbox.com/s/8ubv5if7cbnsjzn/P940-8_front.jpg?raw=1
>>>
>>> Does anyone have an estimate of how many characters X and Y we might
>>> use?
>>
>> Well, ten characters per inch and five lines per vertical inch is
>> readable.   Typewriter spacing...
>>
>> More to the point, why do a new screen and protocol for a new box?
>> Could you go to USB or Bluetooth for the communication, and source a
>> display (like a tablet, or electronic picture frame, or just an app for
>> a cellphone) that has builtin software support?
>>
>> Doesn't it make more sense to use a mass-produced  standard software
>> target instead of a novel build-from-sticks hardware assembly?
> 
> USB interface is a good idea.

For what timeframe?  Where will USB be in 10 years?  Will you even be
able to buy a computer with a USB interface?

> However, you need a computer which is not so
> useful for rack mount installations. Also, you must download and install
> the software on each computer that could be used.

That's ancient thinking.  You need "something" to act as an agent
between the display and device.  If you think in terms of a single
device, then there is pressure to integrate that agent in the
device -- or the display.

But, it can reside in a third location -- one that is more accessible
to a variety of devices and displays!

E.g., let <something> talk to your devices and (possibly) present a
web interface to *any* hardware UI (tablet, PC, phone) that wants
to interact with your device.  Now, you care less about Android vs.
iOS; Mac vs. PC; computer vs phone; big vs small screen; etc.

And, solve that problem *once* and it won't care when your Windows 27
PC with *3D* display comes along!

> Microsoft 11 is making it
> very difficult to install non-approved software. You can run linux, but
> then you need a version of software that runs on different flavors. You
> could attach to a smartphone, but again you need different versions. You
> could use bluetooth instead of USB, but you still have to download and
> install software for sifferent hosts.
> 
> Running software on a host computer is a very bad idea.

Indeed -- doing so the way you envision!

On Saturday, March 5, 2022 at 4:44:49 PM UTC-5, Mike Monett wrote:
> whit3rd <whi...@gmail.com> wrote: 
> 
> > On Saturday, March 5, 2022 at 11:25:51 AM UTC-8, 
> > jla...@highlandsniptechnology.com wrote: 
> >> We're designing a new rackmount box, basicly a fancy power supply, 
> >> with an 800x480 4.3" LCD on the front. Roughly this: 
> >> 
> >> https://www.dropbox.com/s/8ubv5if7cbnsjzn/P940-8_front.jpg?raw=1 
> >> 
> >> Does anyone have an estimate of how many characters X and Y we might 
> >> use? 
> > 
> > Well, ten characters per inch and five lines per vertical inch is 
> > readable. Typewriter spacing... 
> > 
> > More to the point, why do a new screen and protocol for a new box? 
> > Could you go to USB or Bluetooth for the communication, and source a 
> > display (like a tablet, or electronic picture frame, or just an app for 
> > a cellphone) that has builtin software support? 
> > 
> > Doesn't it make more sense to use a mass-produced standard software 
> > target instead of a novel build-from-sticks hardware assembly?
> USB interface is a good idea. However, you need a computer which is not so 
> useful for rack mount installations. Also, you must download and install 
> the software on each computer that could be used. Microsoft 11 is making it 
> very difficult to install non-approved software. You can run linux, but 
> then you need a version of software that runs on different flavors. You 
> could attach to a smartphone, but again you need different versions. You 
> could use bluetooth instead of USB, but you still have to download and 
> install software for sifferent hosts. 
> 
> Running software on a host computer is a very bad idea.

What???  Here is a computer... 

https://upload.wikimedia.org/wikipedia/commons/f/f1/Raspberry_Pi_4_Model_B_-_Side.jpg

Or most likely his box has a zynq running linux on one processor.  Then it just needs a USB connector on his card.  

Running linux solves a lot of mess with writing your own software for anything other than your application. 

I like the way Larkin asks us what length string he should use without any details on what he needs.  My preference these days is to make text as large as possible.  So the text size would depend on what is required to be displayed and what will fit. 

-- 

Rick C.

+ Get 1,000 miles of free Supercharging
+ Tesla referral code - https://ts.la/richard11209 

On Saturday, March 5, 2022 at 1:44:49 PM UTC-8, Mike Monett wrote:
> whit3rd <whi...@gmail.com> wrote: 
> 
> > On Saturday, March 5, 2022 at 11:25:51 AM UTC-8, 
> > jla...@highlandsniptechnology.com wrote: 
> >> We're designing a new rackmount box, basicly a fancy power supply, 
> >> with an 800x480 4.3" LCD on the front.

> > More to the point, why do a new screen and protocol for a new box? 
> > Could you go to USB or Bluetooth for the communication, and source a 
> > display (like a tablet, or electronic picture frame, or just an app for 
> > a cellphone) that has builtin software support? 


> USB interface is a good idea. However, you need a computer which is not so 
> useful for rack mount installations.

Any smart device in a big rackmount box has probably got some microprocessor
inside (what generates the characters otherwise?).    
What I'm wondering, is if there's a USB-slave display device, with non-proprietary  
standard I/O protocols, that can serve.   Displays can fail, it'd be nice if they were 
easy to replace ten years from now.   Can you get a replacement for a ten-year-old
black/white LCD, and its attached backlight nowadays?  Pin-compatible? 
For a USB mouse or keyboard, you CAN get the replacement.

Doesn't have to be USB, of course; bluetooth board in an Arduino would also
suffice to drive a slide-show (slow changing) display.  It'd need a power supply, too, then.
Firewire would have been perfect (lots of bus power available, isochronous transport),
but it's kinda dead these days.

>Also, you must download and install 
> the software on each computer that could be used. Microsoft 11 is making it 
> very difficult to install non-approved software. You can run linux, but ...

Oh, no, the whole purpose is defeated if you put a bunch of licensed specific-version
general-purpose-computer OS software in the middle.   It's a tethered display
problem, devoid of a deep string of software dependencies, that is under consideration.

I want a kind of micro- display standard socket.  It could be TTY emulator, or VGA.
That can be supported long-term.

> Running software on a host computer is a very bad idea.
I presume you mean a remote server computer?   Well, yeah.   Go
too deep with infrastructure, then Ukraine gets invaded and Ne gas 
becomes unobtainium...

On Sat, 5 Mar 2022 15:43:37 -0700, Don Y <blockedofcourse@foo.invalid>
wrote:

>On 3/5/2022 2:25 PM, whit3rd wrote:
>> Well, ten characters per inch and five lines per vertical inch is readable.   Typewriter spacing...
>
> From what distance?  I.e., when you put a display ON a bit of kit,
>you are essentially defining how/where you expect the user to
>interact with it.  If the user has other ideas, he's SoL (or,
>your sale is lost to a competitor that accommodates his needs).


The user would have to be close enough to push the buttons and twirl
the spinner knob.

>
>> More to the point, why do a new screen and protocol for a new box?  Could you go to USB or
>> Bluetooth for the communication, and source a display (like a tablet, or electronic picture frame,
>> or just an app for a cellphone) that has builtin software support?
>
>Unless you are painting on a predefined "virtual display", you're going to
>end up designing some display software.
>
>Increasingly (almost to the point of being ubiquitous), devices are
>shedding *their* displays in favor of some "remote" display/control
>capability.  Devices look, more and more, like client (or, servers
>if you're uncomfortable with the display-as-server model).
>
>I.e., you expose the interface to the "back end".  This leaves you with
>the task of designing a server that can harvest the information desired
>and present it on *it's* UI.
>
>And, if you stop thinking like an equipment manufacturer but, instead,
>see your role in a *system*, then you can imagine the UI might NOT
>want to conform to your idea of what the user *might* want to see
>on a screen and, instead, let the user *build* an interface that suits
>his needs.
>
>Possibly simultaneously displaying information from other devices
>(of which you may be ignorant!).
>
>Isn't it annoying to have to deal with a variety of devices, each with
>their own notion of *how* you should interact with them?
>
>[Do you display the time-of-day?  date?  what timezone?  what format?
>etc.  Do you really want to be making that decision for the user and
>annoying him at your lack of foresight for *his* needs?  "Why are
>the timestamps on your device skewed with respect to those on this
>other device?"]
>
>When I designed the UI for my disk sanitizer, I initially tried to
>cram as much information on a "standard" display as possible.  So,
>an "operator" could look at the state of all 60 disks at once in
>order to get an idea as to their progress, completion times, failure
>rates, etc.
>
>But, there are countless collections of data that might be of interest;
>what if the Operator wanted to focus on a *single* disk?  What if he
>wanted to see it's historical performance depicted graphically instead
>of a "current state"?  What if he wanted to *compare* two disks to
>highlight differences?  What if he has a second such system -- another
>60 spindles -- that he wants to monitor from the same point?  What
>if that point is his *home* (cuz he doesn't want to sit around for
>13 hours waiting for the process to play out)?  etc.
>
>So, the smart solution is to separate the display from the device and,
>once that connection has been abstracted/virtualized, spend effort on
>ADDING VALUE to the UI beyond what you *thought* was appropriate.

It's just a power supply. People want to see volts and amps.

So much philosophy, no numbers.



-- 

I yam what I yam - Popeye

On Sat, 05 Mar 2022 20:30:16 GMT, Jan Panteltje
<pNaonStpealmtje@yahoo.com> wrote:

>On a sunny day (Sat, 05 Mar 2022 11:25:36 -0800) it happened
>jlarkin@highlandsniptechnology.com wrote in
><4cd72hleqqcmvfjmkevjqqaj6isv15tah7@4ax.com>:
>
>>We're designing a new rackmount box, basicly a fancy power supply,
>>with an 800x480 4.3" LCD on the front. Roughly this:
>>
>>https://www.dropbox.com/s/8ubv5if7cbnsjzn/P940-8_front.jpg?raw=1
>>
>>Does anyone have an estimate of how many characters X and Y we might
>>use? We'll try to fire it up next week and experiment, but I'd like to
>>start thinking about screen layouts and have no idea about what might
>>be reasonable. We'd want good visibility so wouldn't want anything
>>really tiny.
>>
>>I'd prefer a fixed-size, fixed-pitch font, to keep the design simple.
>>We might have some characters/boxes with different background colors.
>>
>>The off-screen (mechanical) pushbuttons will be page left/right and
>>cursor up/dn/left/right, and a spinner knob. There will be some box
>>overhead pages and one page per plugin board.
>
>If you do not need graphics then that resolution is probably overkill
>
>128x64 LCD:
> http://panteltje.com/pub/gamma_soectrometer_IMG_4505.JPG
>
>640x480 same font...
> http://panteltje.com/pub/xvtx-p.gif

Is that 40x20 characters? Looks readable.

I could do something like 50x24 or 50x20 chars on my 800x480 LCD.

That's actually a lot for my power supply thing. I might have as many
as 8 channels per board/screen, one line each. Or even 12.

>
>Make a drawing to size first?

I was trying to guess how many chars might work X and Y first.

We could design the screens with Word and a fixed-pitch font, text in
a box or something.

>
>There are a million fonts to chose from, some are free.
>Some LCDs have their own character set.
>Does it run an OS? Linux Xwindows has many fonts
>

The box will use a microZed board, running linux. The display
controller will be an FT800 chip, with an SPI interface from the zed.
We've done this before, just not with such a giant display.



-- 

I yam what I yam - Popeye

On Saturday, March 5, 2022 at 6:10:53 PM UTC-5, whit3rd wrote:
> On Saturday, March 5, 2022 at 1:44:49 PM UTC-8, Mike Monett wrote: 
> > whit3rd <whi...@gmail.com> wrote: 
> > 
> > > On Saturday, March 5, 2022 at 11:25:51 AM UTC-8, 
> > > jla...@highlandsniptechnology.com wrote: 
> > >> We're designing a new rackmount box, basicly a fancy power supply, 
> > >> with an 800x480 4.3" LCD on the front.
> > > More to the point, why do a new screen and protocol for a new box? 
> > > Could you go to USB or Bluetooth for the communication, and source a 
> > > display (like a tablet, or electronic picture frame, or just an app for 
> > > a cellphone) that has builtin software support?
> > USB interface is a good idea. However, you need a computer which is not so 
> > useful for rack mount installations.
> Any smart device in a big rackmount box has probably got some microprocessor 
> inside (what generates the characters otherwise?). 
> What I'm wondering, is if there's a USB-slave display device, with non-proprietary 
> standard I/O protocols, that can serve. Displays can fail, it'd be nice if they were 
> easy to replace ten years from now. Can you get a replacement for a ten-year-old 
> black/white LCD, and its attached backlight nowadays? Pin-compatible? 
> For a USB mouse or keyboard, you CAN get the replacement. 
> 
> Doesn't have to be USB, of course; bluetooth board in an Arduino would also 
> suffice to drive a slide-show (slow changing) display. It'd need a power supply, too, then. 
> Firewire would have been perfect (lots of bus power available, isochronous transport), 
> but it's kinda dead these days.
> >Also, you must download and install 
> > the software on each computer that could be used. Microsoft 11 is making it
> > very difficult to install non-approved software. You can run linux, but ... 
> 
> Oh, no, the whole purpose is defeated if you put a bunch of licensed specific-version 
> general-purpose-computer OS software in the middle. It's a tethered display 
> problem, devoid of a deep string of software dependencies, that is under consideration. 
> 
> I want a kind of micro- display standard socket. It could be TTY emulator, or VGA. 
> That can be supported long-term.
> > Running software on a host computer is a very bad idea.
> I presume you mean a remote server computer? Well, yeah. Go 
> too deep with infrastructure, then Ukraine gets invaded and Ne gas 
> becomes unobtainium...

I don't know why you guys make this so difficult.  Raspberry Pi is as much a standard as any other formal standard.  

https://www.dfrobot.com/product-1784.html

Use this as shown with an rPi piggybacked providing a USB port and you will be able to replace the entire assemblage with a similar unit with whatever rPi is being sold for the next 20 years... and yes, as someone asked, USB will be around longer than RS-232 was popular, partly because it is such a popular standard, and partly because it is so versatile with universally available connectors, etc., etc., etc.  

-- 

Rick C.

- Get 1,000 miles of free Supercharging
- Tesla referral code - https://ts.la/richard11209