capabilities of the board and added components...

so i have this idea.
it involves the board, and SMALL touchscreen lcd, preferably 4", but
we'll see what's available.
it would require 3 "states" of the beagle board a

i tend to diven too far into details- so i'll keep this simple:

is it possible to have the beagleboard work in all the following ways
at the same time?
1. board and lcd are its own computer. you can boot it, use the screen
to navigate. battery or AC power.
2. board and lcd are usb linked to another computer. the screen is now
a seconday display.
3. board and lcd are plugged into the wall and a normal monitor. touch
screen works in similar fashion to #2.

im learning much as i read here, but figured i'd toss this out into
the board.
i know a few people are working on a small, inexpensive touchscreen
lcd option ATM.
if possible, give me an idea on the hardware additions i'm looking at
here....

is it possible to have the beagleboard work in all the following ways
at the same time?
1. board and lcd are its own computer. you can boot it, use the screen
to navigate. battery or AC power.
2. board and lcd are usb linked to another computer. the screen is now
a seconday display.
3. board and lcd are plugged into the wall and a normal monitor. touch
screen works in similar fashion to #2.

Hi JBell,

All three use cases will be possible dependent on the display you choose.
In order to have simultaneous output on your LCD and DVI (use case 3) you
might need to use a SPI LCD on-board, but as long we are talking 3" QVGA or
smaller resolution this should be doable (~1.2Mbit needed pr frame => 24MHz
SPI = 20 fps = OK?) ... Any requirements for the refresh rate on the
on-build LCD?

In case you have further questions please don't hesitate to contact me...

Best regards
  Søren

the lcd header and dvi use the same signals from the omap and the dvi framer doesn’t contain any local framebuffer memory. without some external memory, like some lcds have, it isn’t easy to split up the display refresh logic.

Hi John,

Right now, I've been looking for an LCD with VGA input...but as you
said, I fear doing dual output might be too much.

Right that will be tough - One other option is of cause to use the analog
output together with the DVI output
- Will this work for your application or do you need to have clear digital
images?

I've been looking at 2 different LCD's.
3.5" http://www.lcdtft.com/Detail.asp?Product_ID=090.004_LCD35VGANTS

This one indeed uses the analog input (PAL/NTSC)

5.7" http://store.earthlcd.com/OF-5-7-
VGA;jsessionid=0a010c451f43d4c5e982f82346218ed78a7c38b3ed96.e3eTaxiMa38
Te3qPe0?sc=7&category=12

This uses VGA causing you problems in case you would like to run it together
with the DVI.
Secondly you need a converter from DVI-D to VGA (analog)

SPI, I think you are referring to NOT using the VGA interface, but
rather an LCD more similar to a cell phone option, using a serial

interface?
Right - SPI is basically just 2 serial lines, a clock and a chip select (TX,
RX, CLK and CS) used for transferring data much like for a standard UART
except this is synchronous...

In case of a resolution of 320x240 pixels and a color depth of 16bits/pixel
you would need to transfer 320x240x16 = ~1.2Mbit/frame.
In case you would like a refresh rate of 20Hz (refresh time = 50ms) you
would need a SPI bandwidth of 20 x 1.2Mbit = 24MHz, which is fine within the
limits for the OMAP SPI IP-block
- Max clock rate is 48Mz...

Wrapping up... I think i've come to the conclusion that a NON VGA LCD
would be best. From what I've read, and what you mentioned, the

alternative is an SPI.
Right - Either SPI or analog output...

Any recommendations on tutorials or reading material to get started?

With respect to SPI look at chapter 19 in the TRM (spruf98b.pdf) or

With respect to SPI driven displays search the Internet...
I just found:
Graphic OLED Color Display 128x128 - LCD-00712 - SparkFun Electronics although
it might be too small for you use case?

Best regards - Good luck
  Søren

Søren,

Thanks for the reply again. I follow along with what you're saying. I
can't say i understand
all the acronyms and such (UART, etc), but i get the jist. I'm more of
a front-end developer,
but we all need to lean some how and some time.

I can't use the analog video signal, i need the clarity of digital.
Well, I could use a VGA analog signal, but I think converting from
HDMI->VGA just for a
secondary display is silly when the SPI option is there.

Is there any real benefit of doing SPI over VGA in terms of
performance?

I just found:Graphic OLED Color Display 128x128 - LCD-00712 - SparkFun Electronics
it might be too small for you use case?

Yeah, I'm looking for more of a 3-4". I like the idea of OLED
touchscreen though.

Odds are I'll have to wait for someone to come up with a plug and play
option for SPI lcd's
for developers. Sorta like how Matrix Orbital just signed on.

Gotcha.
Does using SPI eliminate this problem, by using the serial interface
as opposed to the lcd header or dvi?

UART is Universal Asynchronous Receiver/Transmitter commonly known as
a serial port. Since there is no clock line synchronizing the receiver
and transmitter, the interface is asynchronous, and the data signals
are oversampled (commonly 16x the baud rate) and framing bits like
start/stop bits are used to allow the receiver and tranmitter to be in
sync. Many serial ports have a synchronous mode also, and in that
case the receiver and transmitter share a common clock. Chips that
could do both synchronous and asynchronous modes used to be called
more correctly USARTs, although this term has fallen out of favor over
the last couple decades.

-Howard

Hmm - Missed this post some weeks ago...

Is there any real benefit of doing SPI over VGA in terms of performance?

More the other way around - VGA and DVI-D have much higher performance than
a SPI connected display...