2 dotstar on the same clock input

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aloniba
 
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2 dotstar on the same clock input

Post by aloniba »

Hi.

https://learn.adafruit.com/adafruit-dotstar-leds
Is it possible to connect two DotStar LED stripe on the same clock input ?

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bcochran1
 
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Re: 2 dotstar on the same clock input

Post by bcochran1 »

I'm sure you can for example connect two, one meter strips of Dotstar LEDs and use exactly the same signal connections for the entire 2 meter strip. The second one meter strip should not at all need a separate clock signal. Now for full disclosure: I have not yet purchased any Dotstar strips, but I have a plan to do so. I will defer to what the Adafruit support folks say, of course.

Bob

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aloniba
 
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Re: 2 dotstar on the same clock input

Post by aloniba »

Thanks Bob,

But its not what I meant
I'll clarify my question.

Can I connect two parallel DotStar LED stripe, each stripe on different input pin, but with the same clock pin?
the led stripe use 2 pin (command and clock),
I want to connect two stripe and use only 3 pin connections.

Every led stripe will be in a different zone(location)..
barak.

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bcochran1
 
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Re: 2 dotstar on the same clock input

Post by bcochran1 »


Thank you for clarifying it. I think the word "stripe" in your question confuses me. I had thought you really meant the word "strips". So "stripe" still confuses me (smile).

You are asking a very good question. I do not know the answer. I did purchase a 10 pack of APA102C 5050 LEDs (product #2343), plus the companion breakout boards. I soldered one single Dotstar to one breakout board and put it in a breadboard. I've connected a Fubarino SD board to the DotStar -- this uses a PIC32 chip and the MPIDE clone of Arduino. I am working to blink the Dotstar using hardware SPI. So far I have not succeeded because I am not transmitting the APA102 "start", "led", and "end" frames correctly.

Now I suppose I could solder a second DotStar to a breakout board, and try to control this by the same SCK pin on the Fubarino for the clock signal but a different pin on the Fubarino for the data input.

But what if I want to assert a different clock speed for the second DotStar? (Remember...I still do not fully understand SPI or how the DotStar uses its clock signal...I'm just throwing this out for consideration.) Well in this situation I would think that if you want to run two different DotStars using two different clock signals, you will need two different clock pins, too. I'm not saying this is correct -- it is just my theory and it could be wrong. I don't know what the true answer is.

Bob

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pburgess
 
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Re: 2 dotstar on the same clock input

Post by pburgess »

In theory, yes. But our library isn't written to handle this case -- it's strictly one data and one clock pin. You'd need to write your own code to set both data pins as needed for each bit before triggering the clock bit.

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