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Give a Fish, Food for a day, Teach me to fish, I'll have food for life! — Parallax Forums

Give a Fish, Food for a day, Teach me to fish, I'll have food for life!

Kaos KiddKaos Kidd Posts: 614
edited 2006-01-05 20:08 in General Discussion
I believe in the above statement... So...
I'm considering using the following chip : http://pdfserv.maxim-ic.com/en/ds/MAX6955.pdf
To create a "many charactor multi function display"..
Issue is, how many charactors can I display and still achieve some "time" for·scroll functions like·left,right,up, down.
For the life of me, I can't get a handle on how to figure out how many "charactors" I can display, based on the timing requirements of the chip.
I'm looking at this chip because it's got the char rom, full·led drivers in reduced pin count and power requirements, I2C interface ( a max of 16 chips = 128 charactor display ... NICE ...)
Price is USD 15.64 each...
ANother interesting thing is that it can controll upto 128 leds...
that adds up to a real nice and big display (2048!) if you were to max out the system...
And with just a peek outside the box, that could be 2048 SSR's....

Ok, so please, if it's not that hard to explain, would someone show me how to figure out how calculate this stuff, based on the I2C protocall.

Thanks!



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Until our bytes cross again, may your chips never smoke, your bits never fall off, your parts bin never be empty and your jumpers never fall off.
KK
·

Comments

  • PJAllenPJAllen Banned Posts: 5,065
    edited 2006-01-05 00:33
    Well,... OK, but, uh... it'll cost you a fish.

    Actually, I know naught of I2C, but this a neat IC having the 14&16 segment ASCII deal.
  • BeanBean Posts: 8,129
    edited 2006-01-05 01:04
    KK,
    Right on the first page is says it drives up to 16 digits of 7 segment, 8 Digits of 14 or 16 segment displays, or 128 discrete LEDs.
    It also says the character ROM is for 14 & 16 segment display, so there is no character ROM for a matrix display. I assume that's what you are building.

    Bean.

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    http://www.parallax.com/detail.asp?product_id=30012

    "SX-Video OSD module" Now available from Parallax for only·$49.95
    http://www.parallax.com/detail.asp?product_id=30015

    Product web site: www.sxvm.com

    "I hope the goonwave is not vaporware"
    ·
  • Kaos KiddKaos Kidd Posts: 614
    edited 2006-01-05 04:49
    Bean..
    Yes, I've read the entire document. What I'm trying to figure out is how many of these chips I can drive with my BS2P and still have time to "scroll" the display. Looking at it as a 128 led controller, how long will it take to 'shift' in X bits and then turn on the display, leaving some 'housekeeping' time between shifts.
    An example of something I might create with this chip is a 8 row 128 column display.
    I'de need 8 chips... how long will it take the bs2 to load the 1024 bits?
    lets look at doing a 8 X 256 display... 16 chips... do I have enough time to "scroll" the display? How do I find / figure this out.

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    Until our bytes cross again, may your chips never smoke, your bits never fall off, your parts bin never be empty and your jumpers never fall off.
    KK
    ·
  • BeanBean Posts: 8,129
    edited 2006-01-05 13:51
    KK,
    · Okay I think I get what you are asking. But I think your asking it backwords. You keep saying "do I have enough time to scroll", well of course that depends on how fast you want to scroll.
    · So I think the real question is "How fast can I scroll with a 8x128 matrix using the BS2P".

    · Well the help file says that the BS2P I2COut command is 81k Bits per second, and I will assume the chip only needs 1 bit per LED. So for 128 LEDs that would be 128/81000 seconds = 1.58 milliseconds (+ overhead) so if say the overhead is 5 milliseconds that would be 6.58 milliseconds per chip. And 6.58 * 8 = 52.64 milliseconds. Or about 19 updates per second. So if you were scrolling, you could scroll 19 pixels per second (reasonable I think).
    · Now that assumes 5 milliseconds to get the data ready to send to each IC. If it takes longer, just recalculate it.

    · I hope this helps.
    Bean.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    "SX-Video·Module" Now available from Parallax for only $28.95

    http://www.parallax.com/detail.asp?product_id=30012

    "SX-Video OSD module" Now available from Parallax for only·$49.95
    http://www.parallax.com/detail.asp?product_id=30015

    Product web site: www.sxvm.com

    "I hope the goonwave is not vaporware"
    ·
  • Kaos KiddKaos Kidd Posts: 614
    edited 2006-01-05 14:20
    Bean:
    YES, thats the answer (and question!), I was looking for. THe magic number here is 81k per second. I can use that as the constant when trying to calculate some of this stuff. Every time I try to open the help file in the editor, my editor crashes... I don't know why. And for some silly reason, I was thinking in reverse.
    So, to expand on the vary valuable information you provided...
    52.64 ms per chip of 128 leds... * 8 rows of leds = 421.12 ms for a entire display update which = about 2 "frames" per second [noparse]:([/noparse]
    Acceptable animation would be in the 15 to 21 frames per second... Hmmmmm Maybe I need to rethink the whole project...
    THanks Bean!

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔

    Until our bytes cross again, may your chips never smoke, your bits never fall off, your parts bin never be empty and your jumpers never fall off.
    KK
    ·
  • BeanBean Posts: 8,129
    edited 2006-01-05 14:22
    KK,
    · No the 52.64 ms was for all 8 chips for 19 frames per second. Right within your acceptable range.
    ·
    Bean.

    ▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔▔
    "SX-Video·Module" Now available from Parallax for only $28.95

    http://www.parallax.com/detail.asp?product_id=30012

    "SX-Video OSD module" Now available from Parallax for only·$49.95
    http://www.parallax.com/detail.asp?product_id=30015

    Product web site: www.sxvm.com

    "I hope the goonwave is not vaporware"
    ·
  • Tom WalkerTom Walker Posts: 509
    edited 2006-01-05 15:47
    Kaos,
    <FWIW>

    The help-file crash is apparently a known issue (i.e. there are threads referring to it...sorry I don't have a link), but a work around is to open the help file outside of the IDE...at least that is the present work-around while a more permanent and satisfying solution is being pursued...

    </FWIW>

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    Truly Understand the Fundamentals and the Path will be so much easier...
  • Kaos KiddKaos Kidd Posts: 614
    edited 2006-01-05 20:08
    Bean..
    I misunderstood the *8 (I thought that was accounting for the bits)... but, yah, wow... nice...
    And thanks again for pointing that out to me!

    Tom..
    Thanks for the info, I'll try that...

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    Until our bytes cross again, may your chips never smoke, your bits never fall off, your parts bin never be empty and your jumpers never fall off.
    KK
    ·
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