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Incompatible Self-Powered Hub

morgaine

[This thread was split off from an earlier general one about Powered Hubs and has been given a more appropriate subject line.  Note that replies prefix "Re:" to the old subject line.]

 

 

The Pi's very poor power design results in some perfectly good self-powered hubs being incompatible with it.  For example, the cheap little 7-port self-powered Dynamode USB-H70-1A2.0 hub that Farnell advertises as a Pi accessory:

 

 

is not actually Pi-compatible at all, because in addition to powering its 7 host ports, it also powers the Pi board through its A-B upstream lead yet is incapable of supplying enough power to do that successfully (the Pi's Vcc drops to well below 4V).  As a result, when the micro-USB is powered down but the hub is powered up and connected, the Pi ends up rebooting continuously every couple of seconds, potentially leading to destroyed HDMI displays among other worries.

 

So, buying a self-powered hub is not necessarily the end to your Pi power problems.

 

Really the Pi's power design needs to be nuked from orbit and redesigned from scratch.  It's just plain bad in numerous ways.

 

Morgaine.

  • in reply to GreenYamo

    Steve Read wrote:

     

    I guess they can't possibly fully test every bit of kit they hold (Don't they carry 100K + lines?) so it is only down to situations like this that can them aware.

     

    Absolutely.  It's totally impossible (practically and commercially) for them to test their whole product line even superficially, so they have to rely on the product advertising and specifications from each supplier being truthful.  When the supplier neither tests a product for claimed compliance nor checks that what is in the package is consistent with what's written on the packaging, then top tier distributors like Farnell are presented with an impossible problem.

     

    This would destroy their operation if it became common in the industry, because the buck stops with the retailer for end-user sales,

     

    I hope they nail this one.  Dynamode are clearly breaking at least two different advertising and/or trading regulations on this product.