A physical Dummy, Power Usage and MIPI

Discussion in 'Pyra News' started by EvilDragon, Feb 17, 2014.

  1. Neelix

    Neelix Insecticidal Maniac

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    IIRC the charging chip in the pandora is only set to draw up to 500mA on the mini-USB port.   (even if connected to a charger that could supply more)

    I'm not sure what the computer would do if it tried to draw more.  It's a netbook though, so I'm sure it wasn't designed with more than 500mA in mind.

    (Pandora System Info is showing that it is drawing the full 500mA - input: +2510 mW) 

    - Neelix
     
  2. _wb_

    _wb_ Microbe Staff Member

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    I don't think the Pandora can use 5W even with the display at max brightness, wifi active and cpu at 100%. It's only possible to consume that much power if besides all that, you use it to power a power-draining USB device and do some big file transfers from one SD card to the other.
     
  3. _wb_

    _wb_ Microbe Staff Member

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    Yes, I don't think it ever draws 1A from mini-USB.

    Still, >2W is quite a lot of power consumption for the Pandora. It means Widelands was keeping the cpu very busy.

    With a µUSB charger we can get 900mA while transmitting data or 1.5A while charging only. I think 7.5W should be enough to make the Pyra charge even when heavily used -- or else the battery would only last a couple of hours, even if it would be a 8000mAh one (8Ah at 3.7V is 30Wh, so if it uses more than 7.5W, that battery would last less than 4 hours).
     
  4. _jr_

    _jr_ Advanced Member

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    But Widelands is AFAICT a good example of a game that isn't rate limited and would run one core at 100% even on the Pyra.


    Anyway, if the Pyra cannot charge (with highest supported charging current) while using the OTG port (e.g. connected as slave to a PC that only provides 500mA), that would be a major fail.


    Concerning the requirement of three USB ports: while I don't ever use more than one USB port on the Pandora because a powered hub is needed in nearly every situation (power on the OTG port resp. low and full speed support on the large port), it could be more useful on the Pyra in theory, but if I have several components USB anyway the additional hub isn't making much of a difference to me. Especially on the go I usually don't have any additional components with me in the first place (defeating the purpose of having a portable system in the). Therefore I don't see any convincing reason to have more than one full sized USB port *if* that decision reduces the charging capabilities of the device.


    I'm not that much concerned about durability, even my N900 did survive about 1.000 plugging cycles and is just starting to become slightly sensitive (and hopefully lasts until I can get a Neo900). I hope that any solution is much more durable than the known bad implementation of the N900.


    Therefore I could live with charging only over the OTG port *If* it is possible to use a charging adapter in any usage scenario, even though I'd be annoyed any time I had to stop a (long) running transfer, unplug the connection, plug in the charger, replug the connection, and restart the operation (a large copy operation, a video stream, or whatever), just because the battery runs low at an inconvenient time.
     
  5. WizardStan

    WizardStan Mega GP Mania

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    If you try to draw more than has been requested then it is within spec to simply shut the port down entirely. The Pandora doesn't negotiate it's charge rate, it just tries to slurp down 500ma and hopes for the best. Sometimes the PC will give it, sometimes it'll throttle it to 100ma, sometimes it'll just kill the port entirely. It depends on the system.
    There is absolutely no reason to think that it won't be able to charge while being used as a slave, plugged into a PC. That is the default, they would actually have to do something very, very, VERY wrong for that to not work.The question is whether it can charge while acting as a host: plug a USB3 device into it with a special cable so it can get the ultra high speed USB and keep charging at the same time. According to the spec this is possible but not many devices support it and I've never even seen the required cable anyway.
     
  6. _wb_

    _wb_ Microbe Staff Member

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    What would happen if you take a powered USB-3.0 hub and connect it to the Pyra as a host?
     
  7. Neelix

    Neelix Insecticidal Maniac

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    You seem to have missed the context here. It wasn't a question of 'can it charge in slave mode' but 'can it draw enough power to charge in slave mode during periods of heavy usage. In my case (extended Widelands gameplay session) the answer turned out to be no.
    - Neelix
     
  8. WizardStan

    WizardStan Mega GP Mania

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    Ack! Sorry, I misunderstood.
     

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