[Openec] RFC: One-Wire-Filesystem (owfs) for charging battery on XO and openec, (long)

[Albert Cahalan]

On 9/2/07, Frieder Ferlemann <frieder.ferlemann at web.de> wrote:

> The One-Wire-Filesystem allows to access data on 1-wire devices
> as if they were a file within a directory.

nice for debugging

> A task in linux user space would periodically (and/or on
> notification) read the data from the appropriate files
> and based on that give directions to the EC.

Polling is terrible. Waking up the CPU is not much better.

> These directions would tell the EC what to do now and
> what to do next.

Watch out here. Battery condition might suddenly change.
One might even swap batteries.

Consider also the problem of human-powered start-up
from a fully drained battery.

> The resources within the EC are pretty low (RAM is 128 byte
> idata memory, 2kByte xdata memory).
> While one can it is not really a good idea to have floating
> point operations on the EC. (Linux kernel does not either)
> The 2kByte do not allow an elaborated charging algorithm
> to use a longer history.

Note that the gang charger idea also suffers here.
Charging without the OS means charging without
a battery history. Battery changes are trouble too.
One might save battery history on the school server,
but watch out for malicious history.

It's nice to charge without booting Linux.