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Jessie
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Re: micro USB power question.

Sat Nov 12, 2011 10:51 pm

I read in the wiki or the FAQ that the final unit was to be powered by a micro USB power source. Ok so here is the question is that particular port a useable port or is it there for the sole purpose of getting power? For instance on the A model is it the sole port, and on the B model is it one of the two ports?

Here is the reason why I\'m asking. When I get my R-Pi I want to dremmel up a 7 port powered usb hub. I would like only one power cord to go to the unit. Many of the cheap $16 powered hubs I see come with a 5V 2A (10,000 mw) power supply which should be more than enough to power all connected acessories. Now if the micro-USB port is just a dummy port for only powering up the unit then I will just de-solder it and run some copper from the hub board to the R-Pi. If the port is functional I will have to come up with a better solution.

kme
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Re: micro USB power question.

Sat Nov 12, 2011 11:29 pm

The microUSB is a DC port only. Not data lines available.

digital_addict
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Re: micro USB power question.

Sun Nov 13, 2011 1:31 am

First of all I have not done this, neither am I an expert. Having said that this is what I am planning to do when I get my R-Pi. I don\'t want more than one brick in the wall either.

As far as I am aware the micro usb power socket is to replace the coax type on the original board, and is power only.

Assuming that the micro usb socket on the R-Pi has been conventionally connected to the board. i.e., looking at the socket from the front, pin 1 (5v) is on the left. IMO there are 2 ways to solve this issue.

1 Use a type A plug to micro type A plug cable, check that there is continuity between the outer pins of each plug. (there are 5 pins in a micro plug) You will then have to open the usb hub and solder a link between the data pins at the back of the chosen socket. This may or not be possible.

2 Take 1 type A plug with wire attached, and 1 type A micro plug ditto. Connect the 2 red wires together and likewise the 2 black. The green and white white wires on the type A plug end must also be soldered together, whilst the other 2 can be taped up. All joints must be insulated as you must try to reconnect the shield mesh otherwise you could introduce RFI into the R-Pi\'s power supply and this could cause havoc.

hippy
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Re: micro USB power question.

Sun Nov 13, 2011 10:46 am

The micro-USB socket is reported as power only.

How easy it is to remove the socket and solder wires direct to PCB pads or tracks remains to be seen. It may be possible to wire to the PCB without removing the socket and the power supply wires don\'t necessarily have to go to that socket; it may be best they don\'t if you want to bypass the on-board over-current fuse. It may be possible to inject power into the host USB sockets or via the GPIO header pins.

The easiest approach will likely be to find a micro-USB plug/cable with \'flying leads\' to provide power via the fitted socket.

The micro-USB socket, even though it\'s not using the data lines, will likely have pads for the socket pins if only for mechanical rigidity. It may therefore be possible to wire the data lines from a host USB port to that socket. There may however be issues if using a USB charger ( shorting of data lines ).

We won\'t really know what we can and cannot do or how easy or not those things are until we have further details of the redesigned circuit and PCB.

obarthelemy
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Re: micro USB power question.

Sun Nov 13, 2011 11:38 am

Is it important ? I\'d just gut an A-to-micro cable. Off with its head ! (on the A side). Not touching the board side and connector.

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Jongoleur
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Re: micro USB power question.

Sun Nov 13, 2011 12:21 pm

When I get MY Pi, I\'m going to use it for a while, then decide on how to customise it. I\'ve got some ideas, but take a soldering iron to (possibly) a Mk 1 from the first batch? Not bloody likely!

Anyhow, I seen to recall that once the board layout has been finalised, details will be released for projecteers to plan ahead. When we get that, we\'ll know better what needs to be done to butcher the poor thing.

Edit: @obarthelemy: Off with its head? You\'ll have to identify which conductors carry the voltages in the cable. I suppose the easiest way would be to leave a little cable on the A side and strip the wires. Some probing wiith a multimeter between the A connector pads and the individual cable ends should settle the problem.... 8-)
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abishur
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Re: micro USB power question.

Mon Nov 14, 2011 3:26 am

It may just be a micro usb form factor, but it will still follow the usb micro standards. That means you don\'t have to do any probing, you just need to google \"usb pinout\" and it will tell you which color wire is which.
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Jongoleur
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Re: micro USB power question.

Mon Nov 14, 2011 6:53 am

I suppose it depends on where you source the USB lead you want to cut up, but I\'d rather NOT take for granted that whoever manufactured the cable stuck to a wire colour protocol. In my experience, its not unknown for internal wiring that the end-user is never meant to see to be consistent but not follow a standard. Wiring colours in moulded mains leads is one thing, but low voltage/signal connectors? I\'d test before use!
I'm just a bouncer, splatterers do it with more force.....

tufty
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Re: micro USB power question.

Mon Nov 14, 2011 7:49 am

[quote]Quote from hippy on November 13, 2011, 10:46
It may be possible to inject power... via the GPIO header pins.[/quote]
ISTR Gert saying relatively recently that there would be 2 x +5v points on the GPIO part of the board which could be used for injecting power. As I recall it, his words were along the lines of \"there is no \'in\' or \'out\' on a copper track\". Obviously, their existence is very much dependent on the final layout, and, even assuming those points do exist on the delivered product, suitability / precautions required for any given purpose will vary depending on the placement of the various protection (overvoltage, overcurrent) measures.

Simon

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Montekuri
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Re: micro USB power question.

Mon Nov 14, 2011 11:27 am

I think all this questions are aswered in the \"official\" topic about Raspberry Pi power supply:
http://www.raspberrypi.org/forum?mingle ... opic&t=809

langlo94
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Re: micro USB power question.

Mon Nov 14, 2011 5:11 pm

Could we just connect the power to one of the usb ports, infinite power.

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abishur
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Re: micro USB power question.

Mon Nov 14, 2011 7:07 pm

[quote]Quote from Jongoleur on November 14, 2011, 06:53
I suppose it depends on where you source the USB lead you want to cut up, but I\'d rather NOT take for granted that whoever manufactured the cable stuck to a wire colour protocol. [/quote]

Eh, it\'s certainly a good practice, but in all the many, *many* cables I\'ve dissected over the years I\'ve never had someone use the right colors in the wrong places. I\'ve had completely wrong colors (in which case I had to test them out to see which pin went to which wire), but never the official colors in the wrong places. ;)

@langlo - my goodness, the implications of this infinite energy source are staggering!
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