HP 50G USB power & running faster - auto shift from 75Mhz to 203Mhz
in [HP48]
|
Prev: SYSEVAL Question
Next: USB Drivers
From: pynnonen on 10 Oct 2006 23:20 If the HP 50G can get its power from the USB, why not also kick up the ARM9's clock from 75Mhz to 203Mhz? When it is disconnnected, drop it back down to 75Mhz. Also, many USB devices charge via the USB port, why not do the same for the HP 50G? Also, I called the HP Help Center, and they were not aware that you could run the HP 50G from the USB. I even tried removing the batteries, and it still worked. If anyone from HP is a calculator engineer, please inform them of this capability. Is the HP 50G USB port High Speed(480Mbs) or Full Speed(12Mbs)?
From: Brion on 10 Oct 2006 23:43 pynnonen wrote: > If the HP 50G can get its power from the USB, why not also kick up the > ARM9's clock from 75Mhz to 203Mhz? When it is disconnnected, drop it > back down to 75Mhz. Also, many USB devices charge via the USB port, why > not do the same for the HP 50G? > > Also, I called the HP Help Center, and they were not aware that you > could run the HP 50G from the USB. I even tried removing the batteries, > and it still worked. > > If anyone from HP is a calculator engineer, please inform them of this > capability. > > Is the HP 50G USB port High Speed(480Mbs) or Full Speed(12Mbs)? I saw severel mentions of the ability to power the 50g from the USB port, but when I tried to confirm that on the HP Calc web site or in the two on-line manuals, there is no mention of it. If the calc could also charge (NiMH) batteries from the USB port, I would buy it even though I have an hp49g+. That may be too hard for them to do - most devices I know of that charge their batteries from USB power are Li-ion based. Brion
From: The Maverick on 11 Oct 2006 00:59 pynnonen wrote: > If the HP 50G can get its power from the USB, why not also kick up the > ARM9's clock from 75Mhz to 203Mhz? Because you can't clock the memory reliably at that speed. I did a variety of tests using one of the overclock utilities a few months ago .... the highest speeds that were reliable didn't actually make much difference to the calculation speeds. In the end I just went back to good old 75 MHz.
From: bokubob on 11 Oct 2006 01:14 The charger for a motorola razr (at least the version I have) has a usb connector on the end that is the same one that the 50G has on it. So, if you just want a power supply, you could pick up one of those I suppose (though I don't have a 50G to test this idea) pynnonen wrote: > Also, many USB devices charge via the USB port, why > not do the same for the HP 50G? If we're charging batteries with the usb port, then I suppose they don't "need" to be AAA (though there are nice things about such batteries) we could have a li-ion pack. With a li-ion pack, it doesn't need to be so thick.... how about a flat, thin 50G the size of a 42s? Before we go on about how great AAAs are, consider all of the car and portable chargers out there. For instance: http://www.instructables.com/id/EGBQJPLCB2EP287KTZ/ -Jonathan
From: James M. Prange on 11 Oct 2006 01:41
pynnonen wrote: > If the HP 50G can get its power from the USB, why not also kick up the > ARM9's clock from 75Mhz to 203Mhz? When it is disconnnected, drop it > back down to 75Mhz. That's a good idea, if we assume that the *only* reason for choosing to not run the processor at its highest possible speed is to limit battery current. Other possible considerations in choosing the processor speed could include avoiding overheating, working reliably with other hardware, such as SRAM and flash memory, and the correct speeds for the communications ports. I've read that the 49g+ (which implies the 50g as well) can work at higher speeds, but what is the highest speed that it can *reliably* work with, including at the environmental extremes? Do the external communication ports work correctly when the processor speed is increased? Other than that, I'm not so sure that the operating system "knows" where the power is coming from, only what the power supply voltage is. The switch between drawing power from the battery and getting it from the USB port could be entirely in hardware, without ever telling the processor or operating system about it. > Also, many USB devices charge via the USB port, why > not do the same for the HP 50G? That one's easy; other devices that use the USB port are designed to use a particular rechargeable battery, but the 50g is (I assume) designed to use non-rechargeable alkaline cells, although various other batteries do work just fine with it. Designing it to be rechargeable would mean designing it for a particular rechargeable battery, and product safety liability issues would be a consideration. I much prefer the flexibility of having the option to use different kinds of batteries, and if I choose to use a rechargeable battery, then simply use an external charger for it. But although you can't charge the 50g's battery through the USB port, I've read that the serial port connector includes a connection directly to the battery, for the option of powering anything that you choose to connect. You could connect a charger (suitable for whatever rechargeable battery you happen to use) through the serial port connector. > Also, I called the HP Help Center, and they were not aware that you > could run the HP 50G from the USB. I even tried removing the batteries, > and it still worked. > > If anyone from HP is a calculator engineer, please inform them of this > capability. I agree, but I note that within large corporations, the various departments don't always communicate very well. The "help centers", those who write the documentation, the "web masters" who post documentation and revised firmware and applications, and marketing usually aren't as knowledgeable about the actual products as we'd desire. > Is the HP 50G USB port High Speed(480Mbs) or Full Speed(12Mbs)? Good question; I don't know the answer. For all that I know, it might even be Low Speed (1.5Mbps). -- Regards, James |