Plexus/source/Dcf77.spin

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{{******************************************************************************}
{ FileName............: Dcf77.spin }
{ Project.............: }
{ Author(s)...........: MM }
{ Version.............: 1.00 }
{------------------------------------------------------------------------------}
{ DCF77 (clock) control }
{ }
{ Copyright (C) 2006-2007 M.Majoor }
{ }
{ This program is free software; you can redistribute it and/or }
{ modify it under the terms of the GNU General Public License }
{ as published by the Free Software Foundation; either version 2 }
{ of the License, or (at your option) any later version. }
{ }
{ This program is distributed in the hope that it will be useful, }
{ but WITHOUT ANY WARRANTY; without even the implied warranty of }
{ MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the }
{ GNU General Public License for more details. }
{ }
{ You should have received a copy of the GNU General Public License }
{ along with this program; if not, write to the Free Software }
{ Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA. }
{ }
{------------------------------------------------------------------------------}
{ }
{ Version Date Comment }
{ 1.00 20070727 - Initial release }
{******************************************************************************}
{------------------------------------------------------------------------------}
DCF77 is a time signal being transmitted by 'radio'. The time signal being
transmitted is based on an atomic clock.
This code assumes we have a DCF77 receiver with a digital output. This output
is connected to one of the available input pins.
The output pin of the DCF77 receiver changes it output according to the
received radio signal. This radio signal is an amplitude modulated signal.
The amplitude level is converted into a digital signal by the DCF77 receiver.
A typical output signal of a DCF77 receiver is:
┌──┐ ┌──┐ ┌─┐
│ │ │ │ │ │
│ │ │ │ │ │
│ │ │ │ │ │
┘ └─────────────────┘ └───────────────────┘ └──────────────────
The spacing of these pulses is 1 second. Every second the amplitude signal is
being lowered for a small duration (0.1 s or 0.2 s). This lowered amplitude
is being output as a pulse here.
The duration of the pulse defines whether it represents a digital '0' or a
digital '1'.
These digital '0' and '1' together form a digital representation of the time.
This digital stream of bits is being transmitted within one minute. The next
minute a new digital stream starts.
For synchronization purposes there will be no pulse when the 59's digital signal
is being transmitted. This is used to indicate the start of the next digital
stream (and the next minute).
The pulse length is converted into a binary signal according to its length:
0.1s --> '0'
0.2s --> '1'
The digital stream format is (with the first received bit at the right):
5 555555555 44444 444 443333 3333332 22222222 211111 11111
Sec 9 876543210 98765 432 109876 5432109 87654321 098765 432109876543210
D P84218421 18421 421 218421 P218421 P4218421 SAZZAR
30000 0 00 200 1000 2211
R = Call bit (irregularities in DCF77 control facilities)
A1 = '1' Imminent change-over of time from CET <-> CEST
Transmitted 1 hour prior to change (refelected in Z1/Z2)
Z1 = Zone time bit 0 '10' = CET ; UTC + 1 hour
Z2 = Zone time bit 1 '01' = CEST; DST ; dayligt saving time, UTC + 2 hours
A2 = '1' Imminent change-over of leap second
Transmitted 1 hour prior to change (January 1/July 1)
S = Startbit coded time information (always '1')
1 = Minute (BCD)
2 = ,,
4 = ,,
8 = ,,
10 = ,,
20 = ,,
40 = ,,
P1 = Parity bit preceeding 7 bits (all bits including parity equals even number)
1 = Hour (BDC)
2 = ,,
4 = ,,
8 = ,,
10 = ,,
20 = ,,
P2 = Parity bit preceeding 6 bits (all bits including parity equals even number)
1 = Calendar day (BCD)
2 = ,,
4 = ,,
8 = ,,
10 = ,,
20 = ,,
1 = Day of the week (BCD) 1 = Monday
2 = ,,
4 = ,,
1 = Month (BCD)
2 = ,,
4 = ,,
8 = ,,
10 = ,,
1 = Year (BCD)
2 = ,,
4 = ,,
8 = ,,
10 = ,,
20 = ,,
40 = ,,
80 = ,,
P3 = Parity bit preceeding 22 bits (all bits including parity equals even number)
D = No pulse here except for leap second ('0' pulse) -> the next (leap) second
then has no pulse.
The pulse following the 'no pulse' indicates start of next minute/data stream.
The DCF device is connected as follows:
3V3
┌────────┐ 
R │ DCF │ 10k
3V3 ──┳──┳──┤ ├─┻── Input
C  │ device │
┌────┻──┻──┤ │
 └────────┘
R = 1kΩ
C = 1uF + 1nF
The resistor here has one major purpose: filtering out any noise from the 3V3
power supply, which is typically connected directly to the Propeller device.
Since the DCF signal itself is a low frequency (77.5 kHz), it falls within
the frequency range of the Propeller chip itself, which can lead to problems.
Without this resistor the DCF device was unable to function properly. The
resistor has very little impact on the voltage available to the DCF device.
Because the DCF device draws very little current, the voltage drop over the
resistor is very low (0.08V here).
{------------------------------------------------------------------------------}}
CON
CDcfIn = 22 ' Input pin for DCF77 _>Hive ADM-Port 1 ->Expansionsbus B17
CDcfOut = 24 ' Output pin for DCF77 signal (debug/visualization) ->Hive-Administra-LED
CDcfLevel = 1 ' Level for '1' signal
CNoSync = 0 ' Not in sync (never sync data received)
CInSync = 1 ' In sync (no error since last sync)
CInSyncWithError = 2 ' Not in sync (error since last sync), but time is up to date
CCest = 1 ' CEST timezone (daylight saving time)
CCet = 2 ' CET timezone
CAm = 0 ' AM
CPm = 1 ' PM
VAR
byte Cog ' Active cog
long Stack[26] ' Stack for cog
byte Bits[8] ' Current detection of pulses (bit access)
long BitLevel ' Current bit level (NOT the signal level!)
long BitError ' Current bit status
byte BitNumber ' Current index of bit (== seconds)
' Time settings
byte DataCount ' Incremented when data below updated
byte TimeIndex ' Indicates the active index for the time settings
' Typically the background writes in one of the registers
' and if they all check out it makes them available by
' changing the TimeIndex.
byte InSync ' Synchronization indication
byte TimeZone[2]
byte Seconds[2]
byte Minutes[2]
byte Hours[2] ' 0..23 hour indication
byte HoursAmPm[2] ' 1..12 hour indication (used with AM/PM)
byte AmPm[2]
byte WeekDay[2]
byte Day[2]
byte Month[2]
word Year[2]
{{------------------------------------------------------------------------------
Params : -
Returns : <Result> TRUE if cog available
Descript: Start DCF acquisition
Notes :
------------------------------------------------------------------------------}}
PUB Start: Success
{
DIRA[dcfstart]~~
outa[dcfstart]:=1
waitcnt((clkfreq * 2)+ cnt)
outa[dcfstart]:=0
}
result := Cog := cognew(DcfReceive, @Stack)
{{------------------------------------------------------------------------------
Params : -
Returns : -
Descript: Stop cog and DCF acquisition
Notes :
------------------------------------------------------------------------------}}
PUB Stop
if Cog == 0 ' Only if cog is active
return
cogstop(Cog) ' Stop the cog
{{------------------------------------------------------------------------------
Params : -
Returns : -
Descript: Interfaces to variables
Notes :
------------------------------------------------------------------------------}}
PUB GetActiveSet: Value
result := TimeIndex
PUB GetInSync: Value
result := InSync
PUB GetTimeZone: Value
result := TimeZone[TimeIndex]
PUB GetSeconds: Value
result := Seconds[TimeIndex]
PUB GetMinutes: Value
result := Minutes[TimeIndex]
PUB GetHours: Value
result := Hours[TimeIndex]
PUB GetWeekDay: Value
result := WeekDay[TimeIndex]
PUB GetDay: Value
result := Day[TimeIndex]
PUB GetMonth: Value
result := Month[TimeIndex]
PUB GetYear: Value
result := Year[TimeIndex]
PUB GetBit(Index): Value
result := Bits[Index]
PUB GetDataCount: Value
result := DataCount
PUB GetBitNumber: Value
result := BitNumber
PUB GetBitLevel: Value
result := BitLevel
PUB GetBitError: Value
result := BitError
{{------------------------------------------------------------------------------
Params : -
Returns : -
Descript: Handle DCF reception
Notes : At fixed intervals the DCF input is polled. Every second the
data is checked and the data updated.
This code does not compensate for a leap second. However, this
is handled by a resynchronization.
We use a state machine so we can divide everything up.
Digital output:
On : In sync (no error)
1 Hz : In sync with DCF77 signal (rising edge is start second)
3 Hz : In sync with DCF77 signal (59th second)
Active in first 0.5 second
10 Hz : Previous bit had error
Active in first 0.5 second
20 Hz : Resyncing (waiting for pulse, max 1 s); followed by bit
error signal
This is the only variable in length (time) signal
The last 100 ms of the 2nd 0.5 second contains a small 40 ms pulse
when a binary '1' has been detected (for a '0' no pulse is generated)
If no signal is being received then the following output is
repeatedly generated: 20 Hz (1s), 10 Hz (0.5s), no signal (0.5s)
------------------------------------------------------------------------------}}
PUB DcfReceive | LLocalTime, LIntervalCounts, LState, LWaitInterval, LBitNumber, LBitError, LLevels, LBitLevel, LIndex, LAccu, LParity, LError, LNewData
DIRA[CDcfIn]~
DIRA[CDcfOut]~~
DataCount := 0
LLocalTime := 0
InSync := CNoSync
LNewData := FALSE
LWaitInterval := CNT ' Get current system counter
LState := 99 ' Last state == initiates new state
LIntervalCounts := (CLKFREQ / (1000 / 10)) #>381 ' Interval counts
TimeIndex := 0
LIndex := 1
repeat
' The state machine consists of 100 equal steps
' Each of these steps have a time span of 10 ms, getting to a total
' of 1 second
waitcnt(LWaitInterval += LIntervalCounts) ' Wait for next interval
' We keep the local time running independent from the received DCF signal
' because that might need synchronization. Only when synchronization has taken place
' the local time is synchronized with the DCF. This only happens every minute, when
' the received data checks out correctly
LLocalTime++
case LLocalTime
001: ' Update local time
' Note: the date is not adjusted
if Seconds[TimeIndex] == 59
Seconds[TimeIndex] := 0
if Minutes[TimeIndex] == 59
Minutes[TimeIndex] := 0
if HoursAmPm[TimeIndex] == 12
HoursAmPm[TimeIndex] := 1
if AmPm[TimeIndex] == CAm
AmPm[TimeIndex] := CPm
else
AmPm[TimeIndex] := CAm
else
HoursAmPm[TimeIndex]++
if Hours[TimeIndex] == 23
Hours[TimeIndex] := 0
if WeekDay[TimeIndex] == 7
WeekDay[TimeIndex] := 1
else
WeekDay[TimeIndex]++
else
Hours[TimeIndex]++
else
Minutes[TimeIndex]++
else
Seconds[TimeIndex]++
100: LLocalTime := 0
' Handling the 0/1 detection
' We allow a 10% margin of error:
' 0 .. 0.3s 0/1 signal detection
' 0.3 .. 0.9s signal must be 0
' 0.9 .. 1 s not checked
' 1 .. 2 s only when resync active
LState++
case LState
01..30 : if INA[CDcfIn] == CDcfLevel
LLevels++ ' We only need to check one level
31..90 : if INA[CDcfIn] == CDcfLevel
LBitError := TRUE ' Any signal here is an error
101..200: if INA[CDcfIn] == CDcfLevel
LState := 0 ' Restart state machine
' We divide the second up into several parts, including handling data of the
' previous second.
' In the last state (100) data from the current second are copied to the data
' which is handled the next second
case LState
091: if (LLevels => 15) ' Decide if we detected a binary '0' or '1'
LBitLevel := TRUE
Bits[LBitNumber / 8] |= (1 << (LBitNumber // 8))
else
LBitLevel := FALSE
Bits[LBitNumber / 8] &= !(1 << (LBitNumber // 8))
092: ' Check for illogical data (this might also be the missing pulse occuring every minute)
if LBitNumber <> 59
LBitError := LBitError | (LLevels =< 5) | (LLevels => 25)
093: ' We can check the received data immediately
' The background operates on the inactive settings
if LBitLevel
LParity++
case LBitNumber
0 : if LNewData ' If new data, switch over to new data set
Seconds[LIndex] := 0 ' Synchronize seconds
' Note: we can not synchronize in the
' 59th seconds because the 'local time'
' state machine adjusts the minutes/hours
' when the seconds reaches '60'
LLocalTime := 0 ' Synchronize the 'local time' state machine
if TimeIndex == 0 ' Switch to different active set
TimeIndex := 1
LIndex := 0
else
TimeIndex := 0
LIndex := 1
InSync := CInSync
OUTA[CDcfOut]~~ ' Output on
LNewData := FALSE
LError := FALSE
15 : ' R = Call bit (irregularities in DCF77 control facilities)
16 : ' A1 = '1' Imminent change-over of time from CET <-> CEST
' Transmitted 1 hour prior to change (refelected in Z1/Z2)
19 : ' A2 = '1' Imminent change-over of leap second
' Transmitted 1 hour prior to change (January 1/July 1)
20 : if !LBitLevel ' S = Startbit coded time information (always '1')
LError := TRUE
17, 42, 45, 50 : if LBitLevel ' Start new data
LAccu := 1
else
LAccu := 0
21, 29, 36 : if LBitLevel ' Start new data and parity controlled data
LAccu := 1
LParity := 1
else
LAccu := 0
LParity := 0
18, 22, 30, 37, 43, 46, 51: if LBitLevel ' 2
LAccu += 2
case LBitNumber
18: TimeZone[LIndex] := LAccu
if (LAccu == %00) or (LAccu == %11)
LError := TRUE
23, 31, 38, 44, 47, 52 : if LBitLevel ' 4
LAccu += 4
case LBitNumber
44: WeekDay[LIndex] := LAccu
24, 32, 39, 48, 53 : if LBitLevel ' 8
LAccu += 8
25, 33, 40, 49, 54 : if LBitLevel ' 10
LAccu += 10
case LBitNumber
49: Month[LIndex] := LAccu
26, 34, 41, 55 : if LBitLevel ' 20
LAccu += 20
case LBitNumber
34: Hours[LIndex] := LAccu
if LAccu > 11 ' 1..12 Hour + AM/PM
AmPm[LIndex] := CPm
else
AmPm[LIndex] := CAm
if LAccu > 12
HoursAmPm[LIndex] := LAccu - 12
else
if LAccu == 0
HoursAmPm[LIndex] := 12
else
HoursAmPm[LIndex] := LAccu
41: Day[LIndex] := LAccu
27, 56 : if LBitLevel ' 40
LAccu += 40
case LBitNumber
27: Minutes[Lindex] := LAccu
57 : if LBitLevel ' 80
LAccu += 80
Year[LIndex] := 2000 + LAccu
28, 35, 58 : if (LParity & %1) <> 0
LError := TRUE
59 : ' D = No pulse here except for leap second ('0' pulse) -> the next (leap) second
' then has no pulse.
' The pulse following the 'no pulse' indicates start of next minute/data stream.
if !LError
LNewData := TRUE
100: ' Copy current second data to data we will be handling the next second
' and (re)set data for next second
if !LBitError ' An error switches to the next state (resync)
LState := 0 ' otherwise restart state machine
BitLevel := LBitLevel
LBitLevel := FALSE
BitError := LBitError
LBitError := FALSE
BitNumber := LBitNumber ' Last to change because foreground might check this one
' to read others
LLevels := 0
if BitError ' A sync error resets the second counter
LBitNumber := 0
if InSync == CInSync
InSync := CInSyncWithError ' 'Out of sync' if we were 'in sync'
else
LBitNumber++ ' Next second
if LBitNumber == 60 ' We could check for leap second here, but ...
LBitNumber := 0
DataCount++ ' Adjust data indicator for foreground
201: LState := 0 ' Resync failed: restart state machine
' Output
' time out biterror sec59 level Note: 'biterror' and 'sec59' never active at same time
' 1 1 1 1 1
' 10 0
' 17 0
' 20 1
' 30 0
' 34 1
' 40 1
' 50 0 0 0 0
' 75 1
' 91 1
' 95 0 0 0 0
' 101 1 1 1 1
' .. t t t t
' 195 0 0 0 0
if InSync <> CInSync ' Only control the output when not in sync
case LState
001 : OUTA[CDcfOut]~~ ' Always on
010, 020, 030, 040: if BitError ' 10 Hz signal (bit error)
!OUTA[CDcfOut]
017, 034, 075 : if !BitError AND (LBitNumber == 59) ' 3 Hz signal (in sync and 59th second)
!OUTA[CDcfOut]
091 : if LBitLevel ' Bit is '1'
!OUTA[CDcfOut] ' Always off
050, 095 : OUTA[CDcfOut]~
101, 105, 110, 115, 120, 125, 130, 135, 140, 145, 150, 155, 160, 165, 170, 175, 180, 185, 190, 195: !OUTA[CDcfOut]