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Why would they make USB current software based?

E

Eli

Super Moderator | Elite Member
So, I usually use a USB cord to charge my Blackberry because its just more convenient than using the AC charger..

Well, with this new laptop, when I would plug my phone in, the phone would give me an error that USB charging current isn't sufficient. WTF?

The phone still charged, just really slowly. I finally got around to installing the drivers, and it works normally now.

But what the hell is the point in that? USB is specced at 5V, 500mA. The computer shouldn't care or control how much of that 500mA is being used. It doesn't matter whether a device is drawing 1mA or 500mA..

😕
 
Originally posted by: Eli
So, I usually use a USB cord to charge my Blackberry because its just more convenient than using the AC charger..

Well, with this new laptop, when I would plug my phone in, the phone would give me an error that USB charging current isn't sufficient. WTF?

The phone still charged, just really slowly. I finally got around to installing the drivers, and it works normally now.

But what the hell is the point in that? USB is specced at 5V, 500mA. The computer shouldn't care or control how much of that 500mA is being used. It doesn't matter whether a device is drawing 1mA or 500mA..

😕
Click to expand...

It's software based because it's easier that way.
 
Wouldn't you want your laptop to prioritize conserving battery power over ensuring the maximum amperage is being pushed out to the USB ports for devices that may or may not be there?
 
Originally posted by: PottedMeat
I thought USB was 5V 100mA initially, then the device can request more current up to 500mA?
Click to expand...
That seems to be the case, but.. why?


Originally posted by: QED
Wouldn't you want your laptop to prioritize conserving battery power over ensuring the maximum amperage is being pushed out to the USB ports for devices that may or may not be there?
Click to expand...
:laugh:

Is the power just dissipating into the air? 😛

No amperage is being drawn when nothing is connected.

However, I suppose you are right, the issue is probably conserving battery life.. If the software can control how much current devices get, it can save battery life.

Still annoying. If my USB device needs 500mA, give it 500mA. Obviously I'm aware that it's going to reduce battery life......
 
Because software is easier to write and deploy than making a whole new standard requiring ALL USB devices to be hardware upgraded to work together.
 
I find this annoying as well. My companies lock down our laptops I can't install the BB software, meaning I can't charge my (personal) BB off of my laptop while traveling for work.
 
That explains why I couldn't get a usb phone charger to work... Bastards

So why do all those USB phone chargers with 20 tips exist? No one can use them...
 
Originally posted by: spidey07
Because software is easier to write and deploy than making a whole new standard requiring ALL USB devices to be hardware upgraded to work together.
Click to expand...

I don't really understand.

Current, in a spec, does not matter. Only voltage does.

If the USB spec is 5V, 500mA.. nothing will draw more than this(unless its a rogue device).

I can understand throttling USB current, maybe, if I were using battery power.. But when I'm plugged in? That's stupid.

I understand that its probably to save battery life overall, but give me more control damnit. If my desktop ever pulled shit like this, I'd de-solder the old USB chip and put a better one in or something. :|
 
Two reasons.

A USB device could be plugged into an unpowered hub. The device needs to be able to negotiate with the host as to how much power it requires. You don't want the USB port to reach it's current limit and trip off, disconnecting the hub and all the other peripherals.

The computer (particularly laptop) may have limited power availability (e.g. battery) and can negotiate with the peripherals to operate in a low power mode under certain circumstances.

When you plug a device in, it should enter a low power mode, and begin negotiating with the hub/host computer as to how much power it requires. Only if the computer tells the device that sufficient power is available, should the device power up into normal operating mode.
 
Originally posted by: Mark R
Two reasons.

A USB device could be plugged into an unpowered hub. The device needs to be able to negotiate with the host as to how much power it requires. You don't want the USB port to reach it's current limit and trip off, disconnecting the hub and all the other peripherals.

The computer (particularly laptop) may have limited power availability (e.g. battery) and can negotiate with the peripherals to operate in a low power mode under certain circumstances.

When you plug a device in, it should enter a low power mode, and begin negotiating with the hub/host computer as to how much power it requires. Only if the computer tells the device that sufficient power is available, should the device power up into normal operating mode.
Click to expand...
I really don't give a shit. This is stupid and annoying, I should not have to install software for a 5V power jack to work properly. :laugh:

I understand the reasons I guess, I just want more control over it.
 
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