[TLC5940] dot-correction and grayscale mode?

Forum 2005-2010 (read only) General Frequently-Asked Questions
1

Hello,
Can you clear me how is difference between 6bits dot-correction and 12 bits grayscale in the case adjust brighness? Can I use dot-correction mode to make RGB LED with 2^18 = 262144 colors? (I don't care about that 12bit > 6bits then have much more colors).
Thanks!

2

Can I use dot-correction mode to make RGB LED with 2^18 = 262144 colors?

No these are not incremental complementary bits.

That is they cover the same region of brightness. If you read the data sheet it is all explained.

3

Thanks!
However, I think TLC5940 should need 8bit for each output that enough to make fullcolor. My project only need 6bit for each. So with 12bit, I will need shift data at 25Mhz to update grayscale so as fastest as possible. Does anyone use TLC5940 at this frequency?

4

So with 12bit, I will need shift data at 25Mhz to update grayscale so as fastest as possible

What makes you say this. The TLC5940 doesn't require this. What is your application?

5

I intend make a clock propeller with only one propeller has 160 RGB LEDs, and turning ~30round/second to make 30hz refresh. That mean, turning each round ~33ms. In fact, I want to time to output all pin is smallest. However I don't know that send data to TLC5940 at 25Mhz is will occurs any problem?
Also, is LED can light if time ON holds ~10us? and how configure TLC5940 to dimming with only 8bit for each output?

6

I intend make a clock propeller

Sorry I don't know what this is. Do you mean a persistence of vision system.

However I don't know that send data to TLC5940 at 25Mhz is will occurs any problem?

You can't do this with an arduino it's clock is only 16MHz so you can't even approach a speed of 25MHz. Is that the shift in bit speed or the refresh rate for the 160 RGB LEDs?

how configure TLC5940 to dimming with only 8bit for each output?

You can't.

7

Sorry I don't know what this is. Do you mean a persistence of vision system.

Yes, it is look like http://www.youtube.com/watch?v=l4F8UbM-1t4

Is that the shift in bit speed or the refresh rate for the 160 RGB LEDs?

25Mhz, it is shift bit speed from MCU to TLC5940, I calculated that hold time ON of LEDs only ~10 ->20us before propeller shift to next position. However I don't know hold time is enough or not to make LED can light? :-?

8

You are going to have to rethink your design, you can't shift data into anything with an arduino at 25Mhz.