• Hardware

  • Controlling 16x LEDs with Bela mini via PD

Hi,
I have a Bela project where my arduino right now manages 16 LEDs by parsing messages it receives via PD from bela. see picture:

it works very well with no latency.

However, I managed to free all the digital pins on the bela so I may as well use the Bela mini's digital outputs to control the LEDs and clean things up.

What I don't understand is, would the bela provide enough current for the 16 LEDs? they'd need to be light up at the same time in certain scenarios (it's a 16- step sequencer interface). The bela will probably also have another USB device attached to it, probably another Bela Mini who acts as slave unit. Is there the risk I'll damage the unit?

The specifications for the LEDs we'll want to use for the final prototype are below, in particular we want to use the RED ones, used with 150ohms resistors..

sorry but I'm new to this. I really appreciate your help.

Cheers

Could I just know if this would be safe to test?
Thanks

You can draw up to 8mA from each gpio, that should be plenty to light up an LED, though it may not be full brightness. Make sure you dimension the resistor so that you don't exceed the current limit.

Ok nice, I was worried because I remembered something like drawing 100mA max from the gpio. I’ll test it and compare to the arduino result, thanks!

It works very well. I noticed a slight increase in CPU when piloting the 16 pins through bela rather than by using the serial output + arduino; around 5% at 16 blocks and 3% at 32/64.
But I guess it’s completely normal since the beaglebone now has to manage the digital output by itself.
Thanks again!

Are you using them at signal rate or at message rate?

And how often are you writing to them?

I’m sending the LED states from PD at BPM rate, 250 BPM max test rate.
So it should be around 133 messages per second sent to the digital outs in total, considering 2(states) x 16(LEDs) x 4.1 (beat rate)