Rockbox mail archiveSubject: Re: rockbox-dev Digest, Vol 77, Issue 9 clock sync suggestions
Re: rockbox-dev Digest, Vol 77, Issue 9 clock sync suggestions
From: Andrew Kemnitz <superbrainak_at_yahoo.com>
Date: Tue, 21 Feb 2012 12:35:17 -0800 (PST)
about the clock syncing with RDS is there a way to make a list for each area and include those on the site, in order to eliminate the wrong time situation? also you could have an option that lets you change the update interval(so it wont ask every minute) and tell you that it has an update and if it is the right time.
about the placing of the RDS option I would say that it would be best to place it in the date and time settings because it is just using radio for the data and not having to do with the broadcast of music or the function of the tuner.
thanks for reading!
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Sent: Monday, February 13, 2012 4:00 AM
Subject: rockbox-dev Digest, Vol 77, Issue 9
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1. Clock sync using RDS (Bertrik Sikken)
In the past week, I have started to look at the possibility of using
RDS to synchronise the clock of a DAP. Of course this is only possible
with a DAP having an RDS-capable FM chip (gigabeat s, sansa clip zip,
RDS sends a CT (clock-time) message once a minute, containing the
current time with one minute resolution:
* date as modified julian date (which is basically UTC date with
* hours and minutes
* local time offset (in units of a half hour)
What I've seen so far is that all-but-one of the strong FM transmitters
in my area (netherlands, at UTC +1:00 right now) transmit a correct
UTC time (including a correct local time offset of +1:00). One FM
transmitter sends local time with a local time offset of +0:00.
So the *local* time is actually correct for all stations I tried.
My proposal is:
** tuner driver side **
Upon reception of an RDS CT message, the RDS code performs basic
checks on the RDS CT packet, like range of hours (0-23) minutes
(0-59) and date (later than 2012-1-1). It then calculates local
time by summing UTC time and offset.
The reception of RDS time is advertised as an RDS event.
The radio API gets a new property to retrieve the RDS time
(in seconds since 1970-1-1 0:00 in local time).
** radio code side **
When the radio code sees that an RDS time was received, the RDS
time is stored along with a timestamp taken from the RTC.
The radio menu gets a new menu, "Sync to RDS time" (or similar).
When the user selects this menu, he/she is presented with a new time,
calculated from the latest received RDS time and the stored RTC
timestamp, and the user can check/confirm before actually updating
* UTC vs local time? Since the raw RDS time + offset is apparently
wrong for some stations, but local time is OK, I propose to send
local time over the tuner api.
* Should we put the synchronisation in some time&date menu, or in
the fm radio menu?
* Should RDS clock sync be automatic or manual? I propose manual
because I don't trust RDS time to be accurate everytime
(because of bad fm reception for example).
Any ideas for changes/improvements on this proposal?
With kind regards,
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