REM 
REM Psion Series MC/3/3a time setting via serially attached GPS receiver that outputs NMEA
REM 
REM Uses the CALL $058B to retrieve the "country data" structure - this includes UTC offset (in minutes) and "Summer Time" flag
REM After opening the serial port we get 255 bytes of NMEA - LOCate GPRMC, get GPS traceable UTC time from next 7-12 bytes
REM calc time (in seconds from 1/1/1970) from that and UTC offset and "Summer Time"
REM (as Hex $nnnnNNNN - split into hi & low part $nnnn & $NNNN or just by simple maths ;-) )
REM call OS function $038B to set the time
REM 
REM Add a "delay processing time" fudge factor of ... 1s?
REM 
REM Time is expressed as:
REM 
REM 1690166270 or $64BDE3F3 (32-bit number) - i.e. split into $64BD & $E3F3 as above
REM 
REM Tested working on the MC/Series 3/Series 3a
REM 
REM Assumes a GPS receiver attached to the serial port, running at 9600 8N1
REM Assumes a GPS fix
REM 
REM Assumes GPRMC or GPGGA sentences which contain UTC time after "GPRMC," or "GPGGA,"
REM 
REM $GPRMC,170805.000,A,5337.5945,N,00300.7381,W,0.00,281.17,250523,,,D*7D
REM $GPVTG,281.17,T,,M,0.00,N,0.01,K,D*34
REM $PGTOP,11,3*6F
REM $GPGGA,170806.000,5337.5945,N,00300.7381,W,2,9,1.13,4.2,M,49.5,M,0000,0000*40
REM 
REM 
REM The "GenGetCountryData" OS call may or may not be meaningless on the MC - certainly its clock has no concept of "Summer Time"
REM like the 3/3a does. So stime% is set to 1 in the MC's OPL to get UTC to BST working (in summer!). Also (obviously!) all the 
REM graphics commands such as gAT, gPRINT, etc. are meaningless on the MC (I also removed them from the Series 3 code too). 
REM 
REM I also had to change the sentence to search for to GPGGA rather than GPRMC on the S3 & MC, possibly something to do with 
REM serial overruns or something else entirely...?
REM 
REM DISCLAIMER: THIS IS BARELY WORKING CODE! There is minimal error checking, lot's of superflous variables & commented out code
REM             Shared in the hope it might prove useful to someone. somewhere ;-)
REM 
REM 
REM  :: Chris Farrow @zedstarr July 2023 ::
REM 
REM 

	PROC main:
	  local w%
		
	  statuswin on :font -$3fff,0
	  w%=gcreate(0,0,416,160,1) :gborder 0 :gtmode 3
	  guse w%
	  gfont 4  
		
	  settime:
	  get

	ENDP

	PROC rsset:(baud%,parity%,data%,stop%,hand%,term&)
	  LOCAL frame%,srchar%(6),dummy%,err%
	  frame%=data%-5
	  IF stop%=2 :frame%=frame% OR 16 :ENDIF
	  IF parity% :frame%=frame% OR 32 :ENDIF
	  srchar%(1)=baud% OR (baud%*256)
	  srchar%(2)=frame% OR (parity%*256)
	  srchar%(3)=(hand% AND 255) OR $1100
	  srchar%(4)=$13
	  POKEL ADDR(srchar%(5)),term&
	  err%=IOW(-1,7,srchar%(1),dummy%)
	  IF err% :RAISE err% :ENDIF
	ENDP

	PROC settime:
	  LOCAL ret%,pbuf%,buf$(255),end%,len%,loc%
	  local ax%,bx%,cx%,dx%
	  local htim&,ltim&
	  local htim%,ltim%,ltim1%,ltim2%
	  local yr%,mo%,dy%,hr%,mn%,sc%,yday%
	  local dy2&,tm2&,tim$(6),time$(12),tim&
	  local cdata$(40),cBuf%,offset%,stime%
	  
	  gat 10,20
	  gprint "Setting system time from attached GPS"
	  
	  rem Get Country Data - find summertime flag and UTC offset
	  cBuf%=addr(cdata$)+1
	  ret%=CALL($058b,cBuf%)
	  pokeb addr(cdata$),40
	  
	  rem summer time bitmap is at addr(cdata$)+26
	  rem UTC offset in minutes is at addr(cdata$)+3
	  
	  stime%=peekb(cBuf%+25)
	  offset%=peekw(cBuf%+2)

	  gat 10,40
	  
	  if stime% AND 1
	    gprint "Summer Time is On, UTC offset is",offset%/60,"hr"
	  else
	    gprint "UTC offset is",offset%/60,"hr"
	  endif
	  
	  gat 10,60
	  
	  gPRINT "Finding $GPRMC sentence in NMEA:"
	  gupdate off
	  
	  LOPEN "TTY:A"
	  REM receive at 9600 with Xon/RTS/CTS h/shake
	  rsset:(15,0,8,1,7,&0)
	  pBuf%=ADDR(buf$)
	  
	  DO

	    REM read max 255 bytes, after leading count byte
	    len%=255
	    ret%=IOW(-1,1,#UADD(pbuf%,1),len%)
	    POKEB pbuf%,len%   REM len% = length actually read
	    loc%=loc(buf$,"GPRMC")
	    
	  UNTIL loc%

	  rem possible alternative method ??? - get systime now and calc offset to UTC??? 
	  rem get systime sometime later, add calculated offset, then set time?

	  tim$=mid$(buf$,loc%+6,6)
	  
	  gat 10,80
	  gprint "UTC is: ";tim$
	  
	  dy2&=days(day,month,year)
	  tm2&=val(left$(tim$,2))*int(3600)+val(mid$(tim$,3,2))*60+val(right$(tim$,2))+1   rem 1s fudge factor

	  if stime% AND 1
	    tm2&=tm2&+3600
	  endif

	  rem time$=hex$(dts&:(dy2&,tm2&)+offset%*60)
	  tim&=dts&:(dy2&,tm2&)+offset%*60
	  
	  htim&=tim&/65536
	  ltim&=tim&-htim&*65536
	  htim%=uadd(htim&,0)
	  if ltim&>32767
      ltim1%=peekb(addr(ltim&))
      ltim2%=peekb(addr(ltim&)+1)
	    pokeb addr(ltim%),ltim1%
	    pokeb addr(ltim%)+1,ltim2%
	  else
	    ltim%=ltim&
	  endif
	  
	  rem create HEX string of 32-bit time value
	  rem split into high 16 bits and low 16 bits
	  
	  rem htim1%=uadd(eval("$"+(mid$(time$,1,1)+"*4096")),eval("$"+mid$(time$,2,1)+"*256"))
	  rem htim2%=uadd(eval("$"+(mid$(time$,3,1)+"*16")),eval("$"+mid$(time$,4,1)))
	  rem ltim1%=uadd(eval("$"+(mid$(time$,5,1)+"*4096")),eval("$"+mid$(time$,6,1)+"*256"))
	  rem ltim2%=uadd(eval("$"+(mid$(time$,7,1)+"*16")),eval("$"+mid$(time$,8,1)))
	  rem htim%=eval("$"+tim
	  rem ltim%=uadd(ltim1%,ltim2%)
	  
	  rem print "htim& ",htim&
	  rem print "ltim& ",ltim&
	  rem get
	  
	  ax%=CALL($0389,0,htim%,ltim%) rem at last! SET THE TIME ;-) 
	  
	  gupdate on
	  giprint "System Time set to "+left$(tim$,2)+":"+mid$(tim$,3,2)+":"+right$(tim$,2)+" UTC"
	  gat 10,120 
	  gprint "Press any key to exit..."

	ENDP


	PROC dts&:(d&,t&)
	  local dt&
	  
	  dt&=d&
	  dt&=dt&-days(1,1,1970)
	  dt&=dt&*86400+t&
	  return dt&
	ENDP