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is this extremely hard to do with the propeller, — Parallax Forums

is this extremely hard to do with the propeller,

Comments

  • cavelambcavelamb Posts: 720
    edited 2012-02-08 18:24
    What exactly is it that you want to do - that you don't know how to do?
  • jvrproductionsjvrproductions Posts: 61
    edited 2012-02-08 18:32
    i want to try to do an flexible rbg led display but i dont know where to start like:
    What may be a better way to do the arrays how many leds may be controlled by one propeller, (Just learning)
  • ElectricAyeElectricAye Posts: 4,561
    edited 2012-02-08 18:45
    jvrproductions wrote: »
    ....[video]http://m.youtube.com/index?desktop_uri=/&gl=US#/watch?v=9TafnBAEoOw[/video]

    This link doesn't show me a video. What are we supposed to be looking at here?
  • CircuitsoftCircuitsoft Posts: 1,166
    edited 2012-02-08 18:46
    http://www.youtube.com/watch?v=9TafnBAEoOw
  • JasonDorieJasonDorie Posts: 1,930
    edited 2012-02-08 18:51
    There are many LED driver chips that take serial data input and do PWM of multiple LEDs, like the Texas Instruments TLC5940. You can chain many of these together and drive them with a Propeller. I have updated a single chip at roughly 17KHz with the Prop, meaning you could easily control 15 of them at 1KHz, 30 of them at 500Hz, and so on. If you want full RGB control, you need 3 of those chips per 16 RGB LEDs.

    And here's the original video link without the "mobile" junk on it: http://www.youtube.com/watch?v=9TafnBAEoOw
  • Martin_HMartin_H Posts: 4,051
    edited 2012-02-08 19:14
    I've controlled 192 LED's with a single propeller chip and I could have done more but got bored of soldering. Here's my build thread.

    http://forums.parallax.com/showthread.php?136152-LED-Marquee-Module-for-Gadget-Gangster-Platform-(w-video)
  • jvrproductionsjvrproductions Posts: 61
    edited 2012-02-09 06:02
    Thank for the help. I was looking on Martin post but I did not on the pictures any led driver? And more questions? I saw yesterday looking around some companies that sold rgd leds that come with its own chip and are connected by 6 cables 4 for data and 2 for power. Is this a better way to do the array or it's better to do cols of LEDs with LEDs drivers and connect the cols to made the rows? Thanks against and sorry for the English .
  • Martin_HMartin_H Posts: 4,051
    edited 2012-02-09 06:15
    I didn't use an LED driver. I did it directly from the propeller chip and scanned the LED's lighting them up four at a time to keep current draw down. A driver chip often can source enough current that you don't need to do this technique. The display looks much brighter as a result. I was only doing a single color LED, but RGB isn't that much harder as it is like controlling three separate arrays at the same time. The biggest challenge is that you'll run out of pins faster.

    A module with a built in driver has the advantage of simplicity and is a turn key solution. You will need to read the module's documentation to learn how to control it, but it will likely be easier than building your own. I built mine from scratch for the challenge and learning it afforded, but that was more my goal than the module itself.
  • jvrproductionsjvrproductions Posts: 61
    edited 2012-02-09 09:13
    Martin_H wrote: »
    I didn't use an LED driver. I did it directly from the propeller chip and scanned the LED's lighting them up four at a time to keep current draw down.
    Martin Thanks for your reply. I want to do this to learn to so i thinks it's better start doing one like the one you did :-) (I am trying to run without walk first.....) What i do not understood its. If you did not use a led driver. How did you get control of each led with so few pins?
    Thanks
    Jose
  • Martin_HMartin_H Posts: 4,051
    edited 2012-02-09 10:52
    jvrproductions wrote: »
    If you did not use a led driver. How did you get control of each led with so few pins?

    That's a good question because at first glance it look like I would need 192 pins to control that many LED's. But there are two ways to increase the number of LED's you can control.

    * First arrange the LED's in a matrix and hook one set of pins to the rows and another set to the columns. Start with all pins set to input, bring a row pin high, now step through the column pins switching from input to low if the LED should be on. Set the row pin back to an input and move to the next row. You can see this technique in my code and in the schematic of my post. For example if you had ten row pins and ten column pins you could control 100 LED's with twenty pins.

    * Second is that I used Charlieplexing where I connected two LED's to the same row and column, but biased them in the opposite directions as alternate columns. This doubles the number of LED's you can control so your twenty pins above is now controlling 200 LED's. The schematic shows how alternate LED's are forward or reverse biased.

    You can go crazy with Charlieplexing and control an even greater number of LED's, but it gets complicated fast. If you want to start simple just bias all the LED's in your matrix the same direction, save Charlieplexing for later.
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