Ready made displays for LEDTRIX

[Wombat]

I found these BiColor matrix displays which are around the $70 mark which could be a good display for an LEDTRIX. They may be a bit little small but could be easily daisy chained to make the display bigger.

They have all of the shift registers and line drivers etc on the board and would seem to me to be very easy to interface with the existing ledtrix boards we have with little code changes (would not need all of the components)

http://www.sureelectronics.net/goods.php?id=147

There is already some other projects and code written around them
http://forums.parallax.com/forums/default.aspx?f=7&m=281259&p=1

what does everyone think? I was thinking of using 1 or two of them for an information board. Tune to 98.5 FM sort of thing or Now Playing signs or a Countdown timer.

They can have up to 4 lines of 8 - 10 characters each line on them or one line of LARGE Characters and could display graphics. Also they are potentially three colors (Red,Green and Both make Orange)

What does everyone think?

[tconley]

by the sound of it you could combine several together.


Cascading function for extended applications.

[Wombat]

yep they are just basically 595 chips 64 bits long with a 4bit binary to set the row you are outputting and two data bits to select the colour on or off (Inverted). Works very similiar to the way the ledtrix works now. The two halves of the display have saparate data llines.

Would need a single pix to run it and slight mods to the code to output the color you want for each pixel on the line. 11 off 10 red 01 green 00 orange. 4 data lines would be needed in total. (two top half two bottom half)

to cascade them just daisychain them like you do with the 595's or renards and output 128 pixels per line instead.

There would be a limit to this as you have to account that each line is only on 1/16th the time so the scanning from the PIX needs to be quick.

Edited: the Logic as it is inverted inputs (High on data means LED off) and each half of display has own red and green data inputs (16 lines each half)

[vairmoose]

If you wanted to have many boards to get to the desired size, how about a pre-control that fed the data for a specific board to each board controller independent of the other boards? Wouldn't this wipe out the limitation on the size? Vixen would then just be feeding the pre-control with the string of data. The Pre-control would break that string into blocks for the specific boards. The board controller then only needs to worry about one board.

Larry

[tconley]

would this system put the same kind of load on the pc as the current ledtriks. I thought the demo was running without a pc.

[Wombat]

There is a circuit for it on this page
http://forums.parallax.com/forums/default.aspx?f=21&m=282223&p=1
shown here:
http://forums.parallax.com/forums/attach.aspx?a=23740

seems to run a parralax controller with an eeprom to store the messages/graphics and is updated via serial comms. there is code there for it too.

[Wombat]

If it was run off the parrallel port then it would have the same loading effect as the LEDTRIX as it has to do all of the work of scanning and outputting the data continuously.

If we used a PIX of some sort and had some eeprom storing the screen data then it could be serially programmed and would only need to be updated when it needed to be changed which would significantly reduce the loading on the PC.

Wombat

[tconley]

That sound like the prevebial holy grail of what every one wants. Or am i wrong?

[Wombat]

it is but it depends on what you want to display. if you just want to show a text.message only you can put a bitmap table in the eprom and then just send it the message to display plus the special formatting codes to do effects etc and colors to display. that limits you to only displaying what can fit in the bitmap table giving limited graphics. otherwise you can send the whole screen one line a time and send the next screen when you want to change it. this wouuld limit updates per sec on serial. its all a bit of a comprimise depending on what we will want to do with them

[tconley]

Could you do someting like what the MPEG compressions does. Where you send the initial image and the just the delta chages as the display is updated. Then periodically you send a fully refresh. This would greatly reduce the amount of bandwidth required. plus there is always the option instead of using a serial connection use one of the modules that will allow ip connectivity. then you have full network speed. When it comes down to it we all tend to use cat5 ethernet cable as our cabeling standard this would just make the most out of it.

[Wombat]

How about this for a mega RGB ledtrix

http://www.sparkfun.com/commerce/tutorial_info.php?tutorials_id=91

now thats a cool coffee table.
Wombat