Raspberry Pi Forums

Hey!

This is my first post on this forum so please forgive me if I fail to comply with any forum specific rules.

I'm trying to build a project which involves a Pi connected to an Arduino over USB and to a Focusrite Scarlett 2i2 over USB as well. A small diaphragm condenser microphone is to be connected to the audio interface and the audio over USB is then further processed by code running on the Pi. The final output involves the Pi sending a command to the Arduino using Firmata.

Now, my question is this. How do I handle the power requirements for both the interface and the Arduino? Will the Pi be able to handle the interface by itself, in case of which, I'll power the Arduino over its own DC adapter? Or if not, is there any recommended USB hub that I can use to handle all the power requirements?

I've gone through the recommended list of peripherals and most are not available locally in India (which is where I am from, by the way) and the Pi Hub which seems to be the cleanest option again isn't available here.

The Pi cannot handle many USB peripherals without getting into power problems, you are right in thinking about a powered hub. But since your hub choices are limited, I think you might be better off studying what the best hubs are that are available to you, and picking one that has lots of good reviews in general, not necessarily for the Pi. You want to make sure that it will not back feed power to the pi, that is the biggest concern that I can think of that can cause problems. also, make sure it claims many more mA than you need for your projects, because most hubs deliver less power than they claim, and it is better to get one with too much power than not enough in the end.

If you have a Linux box ( or already have your Pi) then run the following command to see the power requirements of attached USB peripherals, you can use this to check one at a time.

lsusb -v

Then pay close attention to the lines saying MaxPower= nnn mA

What I do when considering a peripheral, before buying, is put the item name or product code into a google search, along with keywords maxpower and lsusb, and sometimes someone has posted the output from their unit. Often the manuals for peripherals give equivocal information abou the power requirements, I believe the lsusb output is probably the most reliable (someone correct me if I am in wrong in saying that).