WOW-TO: Raspberry Pi B2 USB.power empowerment by software command

 v2.0.0   [ 20150515]

brain1.jpg

pi2.jpg

What you will need:

1 x Raspberry Pi B2

1 x motivated brain (about 2 grams might  be enough)

ressources:

Dear RASBERRY PI B2 fans all over:

I am an admitted RASPBERRY Pi B2 fan.

I found some good instructions in the net, but none of them seemed to fit perfect and was not a 100 % solution. Therefore i wrote this new one. Hope this helps -  where needed.

Feedback and criticism are warmly welcome.

You may comment 365/24 online using: http://docs.google.com 

regards from berlin, germany, europe

may, 2015

contact

e-mail: pimail.project@gmail.com

blog   : http://pimail.blogspot.de/

Why this?

Because of practical considerations for my theoretical “pimail” - ICT4D - project. There must be as few as possible external components. Each component is a risk in an ignorant and illiterate sourrounding.

Power @ USB.ports does not really depend on micro.USB.port input power definition. It's regulated down to a maximum of 600 mA in total for all 4 USB.ports, because of conceptual considerations of Raspberry Pi Foundation in models B+ and 2 as a low power consumer product.

BUT NOTE! There are good news for Raspberry Pi Model B+ and 2. All other models will not work on this! That’s very important to know about!

It is now possible to enlarge the 600 mA output limit, together for all 4 - USB.ports, up to a maximum of 1.200 mA output, in total, for all those 4 USB.ports with only one right placed software command. So you are able to double powersupply of USB.ports.

So you don’t need extra external stuff; and this really made my day.

You can add and empower a maximum of one external USB.drive into your Raspberry Pi B2. Pls, choose a big one, if needed. So, check the data sheet in advance!

And: never use two USB.drives simultaneously, when powered up only by Raspberry Pi B2; this will (probably) not be the right way and this (probably) will NOT work 4u!

Practical hint: If your drive makes a constant sound like “clac,....., clac,...., clac” - it probably does not have enough power and will fail starting. So, let’s provide some more juice!

How to do it right -  Better: how i did it and succeeded (may be, other ways also will lead to the same results):

Take a 4 GB µSD-card and install a fresh Raspbian Whezzy image on your system. I used this one:

FirmwareVersion:

Just empower your Raspberry Pi B2.

Do not insert your USB.HDD here, pls. Leave it outside the USB.port!

Do not configure anything at this time, e.g. with raspi-config. We don't need to do this here! You may do it later of course.

Now let’s call these commands in the SSH session:

sudo bash

cd

sudo nano /boot/config.txt

Right now, here comes the tricky part of the show:

just add the following line at the end of the file.

That’s it and will made your day :)

max_usb_current=1

sudo reboot

Your 4 Raspberry Pi B2 USBports will now have enough “power to empower” your USB.HDD! If you have a powermeter, you can determine, how hungry (in mA) your HDD.

In the beginning, the spin_up phase, some harddiscs will consume lot of energy >1.000 mA. This might be a problem, because of polyfuse; if it is so, pls, change to a modern HDD, consuming loss power and delivering more bytes. I think, there is no better alternative.

What capacity does your HDD have?

Insert your USB.HDD now in any of the 4 USB.ports.

sudo reboot

you may proceed as usual:

sudo apt-get update && sudo apt-get upgrade && sudo rpi-update

sudo raspi-config

sudo reboot

Have fun!

+++

LINKS:

REDDIT - comments, following this posting:

http://www.reddit.com/r/raspberry_pi/comments/31ikze/more_power_for_raspberry_pi_b_and_2_usbports/

EnergiaRocket:

Btw, this still doesn't mean that a single port will give you 1A or more on RPi. My external HDD that consumes 1A doesn't start spinning on RPi, but works with a normal PC or powered hub (or with other external power). The reason for that is probably the fact that RPi sticks to USB 2.0 specs which "limits" power to 0.5A per port.

pelrun

The pi has hardware explicitly designed to double the maximum current available to the usb ports. You still need to have a power supply that can handle the extra load. Additionally, your hard drive can potentially pull a lot more than 1A at spinup, even if only for a tenth of a second, which a powered hub without a hardware current limiter might happily attempt (and possibly successfully supply) but the pi will not.

Other:

http://raspberrypi.stackexchange.com/questions/27708/is-setting-max-usb-current-1-to-give-more-power-to-usb-devices-a-bad-idea

All that max_usb_current=1 does is to set GPIO38 high, which in turn turns on a FET, which connects a second 39K resistor in parallel to an existing one, on pin 5 of U13, the AP2553W6 USB power manager, lifting the current limit from 0.6A to double that (1.2A), see no possible scenario there why the PI resets because of that, except in case the gate of the FET Q4 is somehow shorted to GND. Which could be caused by a production fault. Inspect Q4, as look if there is solder shorting pins together. Also R6 (resistor mounted between gate of Q4 and GND) should be 100K not 0 Ohm. U13, Q4 and R6 should be near the USB ports.

contact: pimail.project@gmail.com ** blog: http://pimail.blogspot.de 

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