From: Alexandre P. N. <al...@om...> - 2007-03-15 01:30:22
|
Daniel O'Shea escreveu: > Alexandre Pereira Nunes wrote: > >> The pxa 255 processor has no battery back power input for the rtc. AFAIK >> the only way would be to keep it standardly fed and in a deep sleep >> mode, which I don't think has been tested and proven to work. >> >> I'm not sure about future gumstix generations. >> > > The PXA270 has a 'Backup Battery Supply' pin? > I did not check, but I don't think it has. It has (almost) bug-free power management tough, a dirty trick of having a super-cap (or perhaps a small batt and another diode) and a diode and a gpio input pin set as an interrupt may work as a poor man rtc backup. Another configuration would even allow for a small rechargeable rtc backup. IIRC, the rtc does not stop (duh!) under deep sleep, and that's supposed (when the gpio sleep mask is correctly configured) to run with < 1 ma power consumption (that was promised for the pxa 255, but it's not tested; other linux ports claims to have it working for pxa 27x tough). As for the current product, I think the options are to have an external time source: either an external rtc, a gps, or a network time source, depending on what's needed. On this list some time ago people posted several suggestions about external rtc models, with it's own battery backup, and communication by means of i2c, spi, or standard bus modes (which could be used by standard gpio pins). - Alexandre |