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Re: RTC Trickle Charge Value




----- Original Message -----
From: "Dave Matlock" <Dave.Matlock@xxxxxxx.com>
To: <dev-etrax@xxxxxxx.com>
Sent: den 2 juli 2003 20:35
Subject: RE: RTC Trickle Charge Value


> My problem is that I was using the 'date -s' command to set the time.
This says it works, but it does not work when I reset the devboard, for
whatever reason.  I used 'hwtestrtc -s' and it works great.  Anybody know
why?
>
> Thanks,
> Dave

The date command only sets the system time but doesn't write the time to the
RTC.
I believe hwclock is the standard tool normally used to set the hardware
RTC on PC:s.

/Johan

> -----Original Message-----
> From: Johan.Adolfsson@xxxxxxx.com">mailto:Johan.Adolfsson@xxxxxxx.com]
> Sent: Wednesday, July 02, 2003 9:47 AM
> To: Dave Matlock; johan.adolfsson@xxxxxxx.com
> Subject: Re: RTC Trickle Charge Value
>
>
>
> ----- Original Message -----
> From: "Dave Matlock" <Dave.Matlock@xxxxxxx.com>
> To: <johana@xxxxxxx.com>
> Sent: den 2 juli 2003 17:08
> Subject: RE: RTC Trickle Charge Value
>
>
> > Johan,
> >
> > I guess I don't understand.  Are you saying the DevBoard82 cannot
> > use the trickle charger, thus the RTC cannot keep time between power
> cycles?
>
> No, the devboard 82 has a battery mounted so you don't need to do
> anything with the trickle charger to make it work.
> Just use hwtestrtc or some other utility to set the RTC and you
> should be fine.
>
> > If I need this functionality, do I need to add the diodes and resistors
> that
> > you are mentioning?
>
> No, the diodes and resistors are built into the DS1302 and there
> is a register setting in the DS1302 that configures how they should be
> connected to give the proper maximum charge current.
> On the devboard_82 it is a non-rechargable battery so the trickle charger
> shouldn't be used at all.
> On the devboard_lx it is a capacitor so enabling the tricklecharger is
> needed to keep time between power cycles.
> (although the capacitor can be replaced with a battery -
>  the PCB is prepared for that)
>
> > Thanks,
> > Dave
>
> /Johan
>
>
>
> > -----Original Message-----
> > From: Johan.Adolfsson@xxxxxxx.com">mailto:Johan.Adolfsson@xxxxxxx.com]
> > Sent: Wednesday, July 02, 2003 12:22 AM
> > To: Dave Matlock; dev-etrax@xxxxxxx.com
> > Subject: Re: RTC Trickle Charge Value
> >
> >
> >
> > ----- Original Message -----
> > From: "Dave Matlock" <Dave.Matlock@xxxxxxx.com>
> > To: <dev-etrax@xxxxxxx.com>
> > Sent: Wednesday, July 02, 2003 1:32 AM
> > Subject: RTC Trickle Charge Value
> >
> >
> > > What value should I use for the DS1302 RTC chip trickle charge in the
> > kernel configuration?  Is only one of the values valid or do they each
> have
> > different functions?
> > >
> > > Thanks,
> > > Dave
> >
> > It depends on if the backup power source to the DS1302 is rechargable or
> not
> > and the maximum charge current for it.
> > If it's not rechargable use 0.
> > If it is rechargable you can choose to have 1 or 2 diodes and
> > 2k, 4k or 8k ohm resistor to reduce the charge current.
> >
> > On a devboard_lx (with capacitor) I suggest: 6
> > Imax = (3.3v-0.7V)/4kohm = 0.65mA
> > (changing to 5 giving Imax = (3.3v-0.7V)/2kohm = 1.3mA
> >  would probably be ok to)
> >
> > On a devboard_82 (with non-rechargable battery): 0
> >
> > /Johan
> >
> >
>
>