time code transmissions

[David Stephenson]

As they were very cheap I bought a DCF77 receiver from aliexpress. It receives the time code transmissions from Mainflingen in Germany on 77.5 kHz (VLF)
https://en.wikipedia.org/wiki/DCF77
The unit comes with a ferrite rod aerial an amplifier chip with a crystal filter (77.5 kHz I suppose) and very little other information. So I have got it to work; here is the code...
I have also attached a picture.

#chip 12F1840,.25
#config osc=intosc,wdte=off,mclr=off,boren=off
' Define HI2C settings
#define HI2C_BAUD_RATE 25
#define HI2C_DATA PORTA.2
#define HI2C_CLOCK PORTA.1
Dir HI2C_DATA in
Dir HI2C_CLOCK in
HI2CMode Master
wait 100 ms
dir porta.3 in 'data pin
dir porta.0 out 'not used
dir porta.4 out 'not used
dir porta.5 out 'not used
set porta.0 off 'pon off=on
set porta.4 off
set porta.5 off
option_reg.7=0
wpua=b'00000110' 'HI2C pins
SL=0x7C 'DISPLAY ID
COMSEND=0x00 'display COMMAND send
DS=0X40      'display DATA send
wait 10 ms
onetwoline 'initialize LCD
wait 10 ms
j=0
kmin1=0:kmin=0
khour1=0:khour=0
kday1=0:kday=0
kmonth1=0:kmonth=0
kyear1=0:kyear=0 'initialize constants

t1con=b'00000100' 't1con.0 timer1 is on/off
pir1.0=0 'set interrupt flag off
intcon.6=1 'enable peripheral interrupts
t1gcon.7=0 'timer1 continuous counting
tmr1l=0
tmr1h=0
t1con.0=1 'timer on
pie1.0=1 'timer1 overflow Interrupt
'start of main loop...
do
xyz:
  do
  if porta.3=1 then exit do
  if pir1.0=1 then exit do
  loop

if pir1.0=1 then 'detected missing pulse at 59 sec
j=59
screen3
pir1.0=0
tmr1l=0
tmr1h=0
goto xyz
end if

if j=59 and pir1.0=0 then
j=0
khour1=khour 'update on minute roll-over
kmin1=kmin
kday1=kday
kmonth1=kmonth
kyear1=kyear
khour=0
kmin=0
kday=0
kmonth=0
kyear=0
end if

tmr1l=0
tmr1h=0
screen3
j=j+1 'j is the second count
  do
  if porta.3=0 then exit do
  loop

id7=tmr1h 'id7=37 is about 150 ms

jj=j-1 'one second ahead!
'binary coded decimal (arrgh!!)
if id7>37 then
if jj=21 then kmin=kmin+1
if jj=22 then kmin=kmin+2
if jj=23 then kmin=kmin+4
if jj=24 then kmin=kmin+8
if jj=25 then kmin=kmin+10
if jj=26 then kmin=kmin+20
if jj=27 then kmin=kmin+40

if jj=29 then khour=khour+1
if jj=30 then khour=khour+2
if jj=31 then khour=khour+4
if jj=32 then khour=khour+8
if jj=33 then khour=khour+10
if jj=34 then khour=khour+20

if jj=36 then kday=kday+1
if jj=37 then kday=kday+2
if jj=38 then kday=kday+4
if jj=39 then kday=kday+8
if jj=40 then kday=kday+10
if jj=41 then kday=kday+20

if jj=45 then kmonth=kmonth+1
if jj=46 then kmonth=kmonth+2
if jj=47 then kmonth=kmonth+4
if jj=48 then kmonth=kmonth+8
if jj=49 then kmonth=kmonth+10

if jj=50 then kyear=kyear+1
if jj=51 then kyear=kyear+2
if jj=52 then kyear=kyear+4
if jj=53 then kyear=kyear+8
if jj=54 then kyear=kyear+10
if jj=55 then kyear=kyear+20
if jj=56 then kyear=kyear+40
if jj=57 then kyear=kyear+80
end if

pir1.0=0 'make sure!
tmr1l=0
tmr1h=0
loop
end 'should never get here

sub screen3
hi2cstart
hi2csEND(Sl)
hi2csEND(Comsend)
hi2csend(0x80) 'first line
hi2cstop
j1=j/10
j2=j%10
hi2cstart
  hi2csend(Sl)
  hi2csend(DS)
hi2csend(khour1/10+48)
hi2csend(khour1%10+48)
hi2csend(32)
hi2csend(58)
hi2csend(32)
hi2csend(kmin1/10+48)
hi2csend(kmin1%10+48)
hi2csend(32)
hi2csend(58)
hi2csend(32)
hi2csend(j1+48)
hi2csend(j2+48)
hi2csend(32)
hi2cSTOP

hi2cStart
hi2cSEND(Sl)
hi2cSEND(Comsend)
hi2csend(0xC0) 'second line
hi2cstop
hi2cstart
hi2cSEND(Sl)
hi2cSEND(DS)
hi2csend(kday1/10+48)
hi2csend(kday1%10+48)
hi2csend(32)
hi2csend(47)
hi2csend(32)
hi2csend(kmonth1/10+48)
hi2csend(kmonth1%10+48)
hi2csend(32)
hi2csend(47)
hi2csend(32)
hi2csend(50)
hi2csend(48)
hi2csend(kyear1/10+48)
hi2csend(kyear1%10+48)
hi2csend(32)
hi2cstop
end sub

sub onetwoline 'initialize display
SL=0x7C 'DISPLAY ID
COMSEND=0x00 'display COMMAND send
DS=0X40      'display DATA send
chht=0x38 'two lines
hi2cStart
hi2cSEND(Sl)
hi2cSEND(Comsend)
hi2cSEND(chht) 'initialize 16x1or2
hi2cSEND(COMSEND)
hi2cSEND(chht+1) '16x1or2
hi2cSEND(0x10) 'osc set to slowest
hi2cSEND(0x77) 'contrast low byte=3 now 5 now 7
hi2cSEND(0x54) 'pwr booster on
hi2cSEND(0x6F) 'follower
hi2cSEND(0x0C) 'on/off
hi2cSEND(0x01) 'clear
hi2cstop
end sub

[David Stephenson]

So what about the UK time signals (MSF on 60 kHz)?
Aliexpress offer a dual frequency (40 and 60 kHz) VLF receiver (the 40 kHz is for the Japanese VLF transmissions). The problem (as ever) is there is little to no information supplied. I tried all possible combinations of pins high and low and could not get it to work. So the solution was to remove the 60kHz crystal and put it onto a DCF77 board (I also swapped the ferrite inductors, but this made little difference).
UK VLF time signals used to be broadcast from Rugby - a nice central location. Now they are broadcast from Anthorn in Cumbria (almost in Scotland) . This is a long way from me in fact the German one is probably nearer (and is definitely more powerful 50kW versus 17kW).

As is to be expected the coding is different. Rather than a missing pulse on the minute MSF60 has an extra long pulse (500ms) on the minute. Other than that it is a mixture of long (200ms) and short pulses (100ms) to give the BCD time (except near the minute there can be 300ms pulses "as a parity check"). The code is below. I used a 12LF1552 (as I have no 12F1840's left). It only has a 8-bit counter (timer0), but with the prescaler (256:1) it is essentially 16-bit (with only the high byte accessible).

#chip 12LF1552,.25
#config osc=intosc,wdte=off,mclr=off,boren=off
' Define HI2C settings
#define HI2C_BAUD_RATE 25
#define HI2C_DATA PORTA.2
#define HI2C_CLOCK PORTA.1
Dir HI2C_DATA in
Dir HI2C_CLOCK in
HI2CMode Master
wait 20 ms
dir porta.3 in 'mclr pin
dir porta.0 out 'pon=power on
dir porta.4 in 'time pulses
dir porta.5 out 'out n/c
set porta.0 off 'pon off=on
set porta.5 off
option_reg=b'00000111'
wpua=b'00000110' 'HI2C pins
wait 20 ms
onetwoline 'initialize LCD
wait 20 ms
jj=0
kmin1=0:kmin=0
khour1=0:khour=0
kday1=0:kday=0
kmonth1=0:kmonth=0
kyear1=0:kyear=0 'initialize constants
tmr0=0
'start of main loop...
do
  do
  if porta.4=1 then exit do 'start of pulse
  loop
tmr0=0
  do
  if porta.4=0 then exit do 'end of pulse
  loop
jj=jj+1
id7=tmr0 'id7=37 is about 150 ms
if id7<110 then screen3
tmr0=0
if id7>110 then 'found minute marker
jj=0
khour1=khour 'update on minute roll-over
kmin1=kmin
kday1=kday
kmonth1=kmonth
kyear1=kyear
khour=0
kmin=0
kday=0
kmonth=0
kyear=0
screen3
end if
'binary coded decimal (arrgh!!)
if id7>37 and id7<72 then
if jj=51 then kmin=kmin+1
if jj=50 then kmin=kmin+2
if jj=49 then kmin=kmin+4
if jj=48 then kmin=kmin+8
if jj=47 then kmin=kmin+10
if jj=46 then kmin=kmin+20
if jj=45 then kmin=kmin+40

if jj=44 then khour=khour+1
if jj=43 then khour=khour+2
if jj=42 then khour=khour+4
if jj=41 then khour=khour+8
if jj=40 then khour=khour+10
if jj=39 then khour=khour+20

if jj=35 then kday=kday+1
if jj=34 then kday=kday+2
if jj=33 then kday=kday+4
if jj=32 then kday=kday+8
if jj=31 then kday=kday+10
if jj=30 then kday=kday+20

if jj=29 then kmonth=kmonth+1
if jj=28 then kmonth=kmonth+2
if jj=27 then kmonth=kmonth+4
if jj=26 then kmonth=kmonth+8
if jj=25 then kmonth=kmonth+10

if jj=24 then kyear=kyear+1
if jj=23 then kyear=kyear+2
if jj=22 then kyear=kyear+4
if jj=21 then kyear=kyear+8
if jj=20 then kyear=kyear+10
if jj=19 then kyear=kyear+20
if jj=18 then kyear=kyear+40
if jj=17 then kyear=kyear+80
end if
tmr0=0
loop
end 'should never get here

sub screen3
hi2cstart
hi2csEND(Sl)
hi2csEND(Comsend)
hi2csend(0x80) 'first line
hi2cstop
j1=jj/10
j2=jj%10
hi2cstart
  hi2csend(Sl)
  hi2csend(DS)
hi2csend(khour1/10+48)
hi2csend(khour1%10+48)
hi2csend(32)
hi2csend(58)
hi2csend(32)
hi2csend(kmin1/10+48)
hi2csend(kmin1%10+48)
hi2csend(32)
hi2csend(58)
hi2csend(32)
hi2csend(j1+48)
hi2csend(j2+48)
hi2csend(32)
hi2cSTOP

hi2cStart
hi2cSEND(Sl)
hi2cSEND(Comsend)
hi2csend(0xC0) 'second line
hi2cstop
hi2cstart
hi2cSEND(Sl)
hi2cSEND(DS)
hi2csend(kday1/10+48)
hi2csend(kday1%10+48)
hi2csend(32)
hi2csend(47)
hi2csend(32)
hi2csend(kmonth1/10+48)
hi2csend(kmonth1%10+48)
hi2csend(32)
hi2csend(47)
hi2csend(32)
hi2csend(50)
hi2csend(48)
hi2csend(kyear1/10+48)
hi2csend(kyear1%10+48)
hi2csend(32)
hi2cstop
end sub

sub onetwoline 'initialize display
SL=0x7C 'DISPLAY ID
COMSEND=0x00 'display COMMAND send
DS=0X40      'display DATA send
chht=0x38 'two lines
hi2cStart
hi2cSEND(Sl)
hi2cSEND(Comsend)
hi2cSEND(chht) 'initialize 16x1or2
hi2cSEND(COMSEND)
hi2cSEND(chht+1) '16x1or2
hi2cSEND(0x10) 'osc set to slowest
hi2cSEND(0x77) 'contrast low byte=3 now 5 now 7
hi2cSEND(0x54) 'pwr booster on
hi2cSEND(0x6F) 'follower
hi2cSEND(0x0C) 'on/off
hi2cSEND(0x01) 'clear
hi2cstop
end sub