just pulled the trigger on a pocket pro

[jusmee]

Originally Posted by omro

Why is the battery power relevant and cause it to die if you're on mains???

Don't know about the PP because I haven't tried it, but on my HP pda, the rate power is supplied by the charger can be exceeded by the power consumed when the processor is very busy. On a really flat battery, I can sometimes plug it in, and it will start to boot, then crash because it depletes the little bit of built up charge. If I leave it charge for 15 - 30 minutes, it will successfully complete the booting (after a reset from the crash)

[omro]

Well I'm hopeful that it'll arrive tomorrow so we shall see. I'm excited.

[DaleDe]

Originally Posted by LoganK

As for mains, the Pocket Pro, as I understand it, only uses the USB port for power. There is no standard way to draw power in this manner other than to connect as a USB device and negotiate with the computer. If the software is broken, then this negotiation cannot take place and the device cannot charge. Furthermore, the device probably disassociates from the computer during the firmware update meaning it is no longer "on mains". Finally, it may be the case that charging/power management is entirely controlled via software. Thus, if the software breaks the device can no longer manage its power settings.

The Pocket Pro has a standard AC charger included with the device. It provides a standard way to power and charge the device via the USB connector, also supplied. A USB connection to a computer can also be used but it is not the _only method_ nor is it the preferred method.

Dale

[Dave_S]

Originally Posted by LoganK

As for mains, the Pocket Pro, as I understand it, only uses the USB port for power. There is no standard way to draw power in this manner other than to connect as a USB device and negotiate with the computer. If the software is broken, then this negotiation cannot take place and the device cannot charge.

It seems that you just described a Catch-22 situation for devices that are solely powered by USB, like keyboards and mice? While negotiation with the computer for power requirements is possible, with no negotiation the device will receive the default full power of 500 ma. whether it actually draws that much or not. That is how USB powered lights and fans receive power from a USB port with no microcontroller involved at all.

[jusmee]

Originally Posted by Dave_S

It seems that you just described a Catch-22 situation for devices that are solely powered by USB, like keyboards and mice? While negotiation with the computer for power requirements is possible, with no negotiation the device will receive the default full power of 500 ma. whether it actually draws that much or not. That is how USB powered lights and fans receive power from a USB port with no microcontroller involved at all.

The are 4 wires. Two for power, 2 for data. It is perfectly possible to use the power wires without any computer connected to the data wires. That's how/why the plugpack can charge the reader via the USB port.

nitpick (sorry): ma is measure of current not power (although there is a direct relationship if the voltage is constant). USB supplies a voltage that is capable of supplying current up to some rated amount. The amount actually drawn can be anything up to that maximum amount.

[LoganK]

Originally Posted by DaleDe

The Pocket Pro has a standard AC charger included with the device. It provides a standard way to power and charge the device via the USB connector, also supplied.

Standard for the device, maybe, but not standard for USB. There are a handful of ways in which the USB client port can detect that a power source is connected rather than a USB host. I was actually unaware that there is now an endorsed method of charging until I went looking as a result of the comments here.

Since it does include an adapter, it is likely that the device will charge, and be powered by, the adapter in all cases. The BeBook comment above would seem to confirm this.

Originally Posted by Dave_S

It seems that you just described a Catch-22 situation for devices that are solely powered by USB, like keyboards and mice? While negotiation with the computer for power requirements is possible, with no negotiation the device will receive the default full power of 500 ma.

It is actually the opposite: the device must draw the minimum until negotiated for more. This generally means 2.5mA (unconnected), 100mA (connected but not negotiated for more), or 500mA negotiation.

Originally Posted by Dave_S

That is how USB powered lights and fans receive power from a USB port with no microcontroller involved at all.

They draw power by taking advantage of the fact that it is difficult (and not entirely necessary) to dynamically limit the current available the the port. As I recently learned, though, the Battery Charging Specification changes the rules slightly.

Originally Posted by jusmee

The are 4 wires. Two for power, 2 for data. It is perfectly possible to use the power wires without any computer connected to the data wires.

Exactly. Although generally against the specification, it is difficult to prevent me from building my USB-powered toothbrush and abusing the USB port.