Hi!
I am playing with Teensy 3.2, Teensy Audio board and APA102 led.
Since common Teensy SPI ports (11 and 13) are taken for audio board needs, I use 7 for data and 14 for clock.
I have two questions.
- for some reason I do need to tell FastLED about pins I’m using - although they support SPI and as I understand FastLED should work without it.
- I’m powering my LED from usb cable. When I plug it in MacBook - everything works fine (red, then green, then blue, then off, 5 secs each). However if I plug it in Xiaomi PowerBank - colors become strange. Instead of red, green and blue - purple, dim red and bright red. Or it may work for a few seconds and then stop lightning up.
What may be the cause of this?
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think about it for a moment - if you don’t tell FastLED which data/clock pins to use it has to pick a set by default (which usually the ‘common’ pair of pins). If you aren’t using the common pair, the library needs to know somehow - so you have to tell it. Don’t worry, if you specify a pair of pins that can be driven by hardware, FastLED will use hardware spi.
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sounds like your power bank is only putting out 100-500mA instead of the 2A+ that you can get out of the MacBook.
Some USB chargers/batteries require you to play some games w/resistors to be able to use higher currents (if they’re even capable of it). You’d have to google around for specifics of how to do that though.
Thanks!
I got it about pins, that’s good news.
Considering power… My single LED uses 60mA max. Could the problem be low load? And I’m pretty sure that my powerbank is strong enough - it charges iPhone very fast.
Yes - but iPhone tells the battery that it wants high current charging. Many USB devices won’t give high current without, as I said above, playing games with resistors on the USB lines. The iPhone absolutely tells chargers/batteries that it wants 1A or 2A charging rates. Also don’t forget that the teensy itself draws power.
Many of those power banks turn off automatically if the load is too low for too long. Common thresholds are in the 100 to 200 mA range.
Thanks, Paul! Some specific numbers like this are very useful.