What Ampere does the Bela want?

William

Hi,

Bela arrived. While I do struggle a bit with the performance (who came up with real time cross convolution anyway?) , I really like the board and the whole workflow.

BTT. I couldn't find any info on what ampere the board (BBB + Bela) takes when powered with the barrel connector. I've read that 1.2A is the minimum for a BBB via the external connector but I don't really understand why the external connector should provide 1.2A even though bela runs on 0.5A via USB without any complaints.

The use case:
I want the bela to power a beatstep (or any other MIDI over USB peripheral). Is it sufficient to provide 1.2A over the connector and then let the bela power the beatstep over midi?

Cheers!

ryjobil

My 300 mA 5V phone charger struggles to keep the voltage at 4.5V and sags when CPU usage goes up. I would say 300 mA minimum to keep Bela going, so the 500 mA USB is probably about perfect for maintaining a stable 5V if not providing power to external devices.

If the external MIDI device or combination of them doesn't want more than 0.5A then a 1.2A supply is probably all you need.

giuliomoro

I measured the current when the CPU was spinning fast and it was about 350mA I think. You may require significantly more if you drive many LEDs, speaker outputs, headphones or other low-impedance loads. The speaker themselves may draw up to ~250mA each which is the main reason why we force you to use the barrel connector instead of the USB B port if you need to use the onboard power amps.
But if you use none of these, then 350mA should be enough for the BBB and the Bela cape alone. It then really depends on how much current the USB device requires, but in principle if it is supposed to be bus-powered, then I would say 1.2A to Bela should be enough for it.

William

Hi, thanks for the detailed response. Hacking can continue this evening then. 🙂