Octows2811 with matrix panel
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brendanmatkin
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Start off on this page for the Octows2811. Make sure to scroll down (there is a white space gap)!
Instead of several rows of strips, just consider the matrix to be a single strip of 256 (8x32).
You might also look at this Adafruit library ( and this guide ).
Instead of several rows of strips, just consider the matrix to be a single strip of 256 (8x32).
You might also look at this Adafruit library ( and this guide ).
GremlinWrangler
Well-known member
For single strip use you can also fastLED http://fastled.io/, and just use one channel of the Octoboard as a handy level converter.
The panel I have is setup to start Left and go Right on the first row which is 8 wide, so 8 columns, 32 rows. In the Plasma Animation example in Octows2811 library I have this definition at the top:
This results in the first 4 rows being lit, so 32 pixels total.
If I change to COLS_LEDs 32 and ROWS_LEDs 8 I get the same exact result.
I'll take a look at Fastled.io, does it use DMA like Octo library? Does it work as quickly?
Code:
#define COLS_LEDs 8 // all of the following params need to be adjusted for screen size
#define ROWS_LEDs 32 // LED_LAYOUT assumed 0 if ROWS_LEDs > 8
#define LEDS_PER_STRIP (COLS_LEDs * (ROWS_LEDs / 8))This results in the first 4 rows being lit, so 32 pixels total.
If I change to COLS_LEDs 32 and ROWS_LEDs 8 I get the same exact result.
I'll take a look at Fastled.io, does it use DMA like Octo library? Does it work as quickly?
GremlinWrangler
Well-known member
Notice the LEDs per strip is divided by 8, so those numbers are assuming you are feeding 8 strands, not a single strand with the other 7 inactive. I think you need tell it you have 8*8 columns as if you had 8 of these stacked up.
FastLED can do DMA but believe it also wants to feed 8 strands because it assumes you are wanting to maximise throughput.
Your speed question is tricky, since OctoWS2811 pixels take a fixed amount of time to update per pixel regardless of the software. The magic of the OctoWS library is that the code does not block while feeding the strand, and you can feed 8 pixels at a time if your pixels array allows. So your refresh rate is can be as high as 1/8 the time to refresh your total pixels with the next frame being prepped while the last frame is read out.
I think you are looking at 10ms refresh for the strand length, so you even with blocking code from another less clever library you could still get a reasonable refresh.
FastLED can do DMA but believe it also wants to feed 8 strands because it assumes you are wanting to maximise throughput.
Your speed question is tricky, since OctoWS2811 pixels take a fixed amount of time to update per pixel regardless of the software. The magic of the OctoWS library is that the code does not block while feeding the strand, and you can feed 8 pixels at a time if your pixels array allows. So your refresh rate is can be as high as 1/8 the time to refresh your total pixels with the next frame being prepped while the last frame is read out.
I think you are looking at 10ms refresh for the strand length, so you even with blocking code from another less clever library you could still get a reasonable refresh.
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