On Mon, Sep 07, 2009 at 04:25:49PM -0300, Werner Almesberger wrote: > Dave Ball wrote: > > > Should the modem be powered from VBAT or VB_GSM? I've just noticed > > that I had assumed the latter, but looking at U1750, VB_GSM is on > > the battery side of the switch, where VBAT is actually the switched > > supply. > > At least the RF amplifier has to be supplied directly from the > battery, because of its high current peaks.
Is it just that we need to find a power switch with lower on resistance? > The question is now > if it even makes sense to provide a means to cut power to the > logic side of the module. Not likely. Someone malicious would have included the necessary voltage regulator to feed the logic side from the RF side supply. > There are two reasons for having such a switch: > > - make absolutely sure the modem can't turn on by accident, and > > - prevent malicious firmware from spying on you (E.g., sending > out your location even if the phone is supposedly turned off.) And three: Making sure the modem actually turns off when you turn off the phone. In the GTA01, it would stay on unless you sent the a...@poff command. -- Rask Ingemann Lambertsen Danish law requires addresses in e-mail to be logged and stored for a year _______________________________________________ gta02-core mailing list [email protected] https://lists.openmoko.org/mailman/listinfo/gta02-core
