' VSX-AMPLIFIER-JUKEBOX (unfinished but works well)
' No Copywrite or restrictions. Completely Free to use. Rodyne.com 2026

' NOTE: Requires a PICO 2 (RP2350) Overclocked to 250Mhz to do the MP3 Decoding.
' The board I am using is a Pimaroni Pico Plus with the 80 pin RP2350B chip so a 
' couple of the pins are different from the normal pico2: We use GP41 instead 
' of GP27 and GP42 instead of GP28 for the analogue inputs, otherwise same as pico2

' SYSTEM COMMANDS BELOW MUST BE RUN FROM PROMPT (NOT PRGM) TO CONFIGURE A NEW 
' BOARD SEE MANUAL FOR DESCRIPTION OF WHAT THEY MEAN:

'OPTION HEARTBEAT OFF             ' Turn off the green flashing light for bedroom!
'OPTION SYSTEM SPI GP2, GP3, GP4  ' Config SPI FOR SD CARD READER
'OPTION SDCARD GP22               ' Config SD Card reader chip select pin
'OPTION AUDIO I2S GP16, GP18      ' Config I2S FOR PCM5102 DAC
'OPTION CPUSPEED 250000           ' Give CPU more umph! to handle mp3 decoding

'Global variables
DIM VFDfont(91) as integer  ' For the VFD display SC16315 chip conv ASCII to font
DIM artists$(400) length 40 ' Upto 400 artists (I have 122)
DIM tracks$(300) LENGTH 128 ' Upto 300 mp3 tracks per artist (128 bytes is max filename)
dim DispStr$                ' What will be displayed on VFD, scrolls if bigger than 8

DIM INTEGER SelectWheelState,PrevGP0,VolumeWheelState,PrevGP1
DIM integer NumArtists,NumTracks,CurrentTrack,CurrentArtist,key3
DIM integer CurrentVolume,CurrentInputSource,ArtistFinished,TrackTimer
dim integer DispPos,TrackSS,TrackMM,LastDP

'memory ' Not sure how big the MP3 buffer needs to be so keep above arrays reasonable

setpin gp6, gp7, i2c2 ' Init PT2259 volume chip - def I2C Addr = &H44 (7-bit)
SETPIN GP10, DOUT     ' SC16315 CLK (IDLE = HIGH - MODE 3)
SETPIN GP5,  DOUT     ' SC16315 STB (IDLE = HIGH)
SETPIN GP11, DOUT     ' SC16315 DIN
SETPIN GP15, DOUT     ' MAINS-POWER RELAY (0=POWER-OFF)
SETPIN GP14, DOUT     ' MUTE SPEAKERS (0=Speakers muted)
SETPIN GP19, DOUT     ' INPUT SOURCE RELAY (GP19=0=I2S, GP19=1=CD OR AUX)
SETPIN GP20, DOUT     ' INPUT SOURCE RELAY (GP20=0=CD PLAYER, GP20=1=AUX)
SETPIN GP0,  DIN, PULLUP  ' ROTARY ENCODE SELECT WHEEL DN (0V ACTIVE)
SETPIN GP21, DIN, PULLUP  ' ROTARY ENCODE SELECT WHEEL UP (0V ACTIVE)
setpin gp0, INTb, SelectWheelInterrupt
SETPIN GP1,  DIN, PULLUP  ' ROTARY ENCODE VOL CONTROL  DN (0V ACTIVE)
SETPIN GP13, DIN, PULLUP  ' ROTARY ENCODE VOL CONTROL  UP (0V ACTIVE)
setpin gp1, intb, VolumeWheelInterrupt
SETPIN GP26, DIN, PULLUP  ' STANDBY "POWER" BUTTON (0V ACTIVE)
SETPIN GP12, DIN  ' IR INPUT (FUTURE USE)
SETPIN GP42, ARAW 'KEY2 (GP28 ON NORMAL PICO) N/U yet 
SETPIN GP41, ARAW 'KEY3 (GP27 ON NORMAL PICO)
                  '


' For the SC16315 VFD Display driver we only need to send clock/data and cs, it is
' SPI protocol but if we use SPI we waste a pin, plus at the time of designing I 
' was not sure I could have the SD Card and the display working together so I thought
' I would not waste a pin and bit bang the data out (not the pioneer does not use the
' SC16315's keyboard scan so we do not need MISO)

SUB SPISendByte(dat) 
  LOCAL i
  FOR i = 0 TO 7
    PIN(GP11) = dat AND &H01  ' Toggle MOSI LSB First
    PIN(GP10) = 0             ' clock hi
    dat = dat >> 1            ' shift bits to ready next bit
    PIN(GP10) = 1             ' clock low
  NEXT i                      ' rinse/repeat until all 8 bits gone
END SUB

' Init the SC16315 VFD Driver (Flowchart on Page 10 of SC16315S datasheet)

SUB InitVFD 
  PIN(GP5) = 0      ' COMMAND: set Display Mode 12 digits/16 segments - last 2 chars n/u
  SPISendByte(&H08) 
  PIN(GP5) = 1
  PIN(GP5) = 0      ' COMMAND: Set data: Write to Display RAM, Auto-Increment
  SPISendByte(&H40) 
  PIN(GP5) = 1
  PIN(GP5) = 0      ' COMMAND 3: Set RAM Address to 00H Auto increment  
  SPISendByte(&HC0) 
  FOR i = 1 TO 36   ' write 0 to all RAM addresses (CLR RAM)
    SPISendByte(0)
  NEXT i  
  PIN(GP5) = 1  
  PIN(GP5) = 0      ' COMMAND 4 : Display OFF
  SPISendByte(&H80) 
  PIN(GP5) = 1  
END SUB

' The display has 12 characters, character 3 and character 12 are the symbols that
' we do not use, the other 10 are split into 8 alphanumeric and 2 numeric as below
'
' +---+---+---+---+---+---+---+---+   +---+---+
' | 11| 10| 9 | 8 | 7 | 6 | 5 | 4 |   | 2 | 1 |
' +---+---+---+---+---+---+---+---+   +---+---+
'
' So to display HELLO we send "H" to char 11, "E" to char 10.. etc

' Each character has up to 16 segments in the SC16315 mode pioneer have used, but
' the SC16315 has upto 24 segments so the last 8bits are not used, thus we have to
' map each ASCII char to a 16 bit (2byte) bitmap this is done in the VFDFont() 
' array so each character is two bytes with the font data and a blank 0x00 byte.
' I'm Pretty sure after the init I dont need to keep sending the COMMANDs for mode 
' and data but that is what the datasheet example says, and it works, so whatever..


SUB PrintVFD dtext$  ' Print text$ on VFD (String of exactly 10 characters)
  LOCAL i, charCode, segData
  dtext$ = UCASE$(dtext$ + "          ")
  PIN(GP5) = 0      ' COMMAND: set Display Mode 12 digits/16 segments - last 2 chars n/u
  SPISendByte(&H08) 
  PIN(GP5) = 1
  PIN(GP5) = 0      ' COMMAND: Set data: Write to Display RAM, Auto-Increment
  SPISendByte(&H40) 
  PIN(GP5) = 1
  PIN(GP5) = 0      ' COMMAND 4 : Display OFF
  SPISendByte(&H88) 
  PIN(GP5) = 1  
  PIN(GP5) = 0      ' COMMAND 3: Set RAM Address to 00H Auto increment  
  SPISendByte(&HC0) 
  i=11
  ' Immediately Send 12 digits using ASCII segment data from font table
  DO while i>0
    charCode = ASC(MID$(dtext$, i, 1))
    IF charCode < 32 OR charCode > 90 THEN charcode = 32
    segData = VFDfont(charCode) ' get ASCII->segment conversion
    SPISendByte(segData AND &HFF)         ' Low Byte (Segments 1-8)
    SPISendByte((segData >> 8) AND &HFF)  ' High Byte (Segments 9-16)
    SPISendByte(0)                        ' 3rd Byte (Extra segments/Icons)
    i=i-1
  LOOP
  PIN(GP5) = 1  
  PIN(GP5) = 0      ' Finally Send instruction for Display ON at full brightness
  SPISendByte(&H8e) 
  PIN(GP5) = 1
END SUB

' The PT2599 has a basic and hard to find datasheet, there is a noticable click
' when I send a command to set the volume, I have tried a few variations on the 
' data sent but dont see an easy way to get rid of it (bugger!) a hard mute input
' would have been too much to ask!
' Looking back I should have used one of the combined volume control, selector 
' chips LCSC seems to have a few of such as the ROHM BD37534FV-E2 as I could have
' also ditched the input relays and had a few more inputs available for lower $ (sigh!)

SUB SetVolume(percent, DoVFD) ' Set Volume between 0% (mute) and 100% (full)
  LOCAL db, tens, ones, tempstr$
  db = 79 - INT(percent * 0.79)
  tens = INT(db / 10) +&HE0
  ones = db MOD 10    +&HD0
  IF percent=0 then
    I2C2 WRITE &H44, 0, 1, &H77 ' Mute ON
  ELSE
    I2C2 WRITE &H44, 0, 3, &H74, tens, ones ' Unmute and set L&R to -20dB
  ENDIF      
  if DoVFD=1 then PrintVFD("VOL: " + str$(percent))
END SUB

' I use two relays to select 3 input sources, the primary one being the I2S DAC so
' I can play my MP3's, but setting relay U15 lets us select the CD input and if you
' also set U11 then the AUX input. So basically we are just toggling 2 GPIO pins

SUB SelectInput(src, DoVFD)
  if CurrentInputSource <> src then
    IF src=1 THEN
      PIN(GP20) = 1 ' 1 = Select CD PLAYER
      PIN(GP19) = 0
      if DoVFD=1 then PrintVFD("SRC: CD ")
    elseif src=2 THEN
      PIN(GP20) = 1 ' 2 = Select AUX
      PIN(GP19) = 1
      if DoVFD=1 then PrintVFD("SRC: AUX")
    ELSE
      src = 0
      PIN(GP19) = 0 ' off/dont-care
      PIN(GP20) = 0 ' 3 = Select MP3 
      if DoVFD=1 then PrintVFD("SRC: MP3")
    ENDIF        
    CurrentInputSource = src  
  endif  
END SUB

' This next bit you just send it a folder name (eg B:/genesis) and it will find
' all the MP3 files under it. eg the next level down is an album folder so we
' will retrieve the tracks under the album folder. eg it will get files like:
' B:/genesis/foxtrot/suppers ready.mp3 or
' B:/genesis/duke (Full album).mp3
' these are populated in the tracks$() array which is cleared as you select the
' artist. I could not see any comments about size restrictions on the PLAY MP3
' so hoping all good long term

SUB GetTrackList path$ AS string, DoPrint AS Integer
  local integer ii, NumAlbum
  LOCAL SubDir$(50) ' Allow upto 50 sub-folders for albums if required
  local string file$
  CurrentTrack=0
  Numtracks=0
  NumAlbum=0
  for ii=0 to BOUND(tracks$())
    tracks$(ii)=""
  next ii
  ' All tracks in root artist folder
  file$=DIR$(path$+"*.mp3", file)
  do while file$<>"" and NumTracks<bound(tracks$())
    tracks$(NumTracks)=path$+file$
    if DoPrint then print " - Add track "+str$(NumTracks+1)+" : '"+tracks$(NumTracks)+"'"
    file$=DIR$()
    NumTracks=NumTracks+1
  loop
  ' Second, find all subdirectories (albums)
  file$=DIR$(path$+"*", dir)
  do while file$<>"" and NumTracks<bound(subDir$())
    IF file$ <> "." AND file$ <> ".." THEN
      SubDir$(NumAlbum)=path$+file$
      if DoPrint then print " +album '"+SubDir$(NumAlbum)+"'"
      NumAlbum=NumAlbum+1
    endif
    file$=DIR$()
  loop
  ' Get all the tracks in these subdirectories
  for ii=0 to numAlbum
    file$ = DIR$(subdir$(ii) + "/*.mp3", FILE)
    do while file$<>"" and NumTracks<bound(tracks$())
      tracks$(NumTracks)=SubDir$(ii)+"/"+file$
      if DoPrint then print " - Add album-track '"+tracks$(NumTracks)+"'"
      file$=DIR$()
      NumTracks=NumTracks+1
    loop
  next ii  
  print "Select Artist '"+path$+"': " + str$(NumAlbum) +" Albums, "+ Str$(NumTracks) + " Tracks"
  print ""
END SUB

sub PlayTrack
  if CurrentTrack<NumTracks then
    play mp3 tracks$(CurrentTrack)
    print "Playing Track " +str$(CurrentTrack+1) + " : "+tracks$(CurrentTrack)
    DispPos=0
    TrackSS=0
    TrackMM=0
    LastDP=0
  ELSE  
    CurrentArtist=CurrentArtist+1
    ArtistFinished=1
  endif
end sub



'###################################
'####  MAIN PROGRAM STARTS HERE ####
'###################################

ProgramInit:

  ' Initialise pin and variables to default states
  
  PIN(GP10) = 1 ' SC16315 CLK (IDLE = HIGH - MODE 3)
  PIN(GP5)  = 1 ' SC16315 STB (IDLE = HIGH)
  pin(gp15) = 0 ' MAINS-POWER RELAY (0=POWER-OFF)
  pin(gp14) = 0 ' MUTE SPEAKERS (0=Speakers muted)
  PIN(GP19) = 0 ' INPUT SOURCE RELAY (GP19=0=I2S, GP19=1=CD OR AUX)
  PIN(GP20) = 0 ' INPUT SOURCE RELAY (GP20=0=CD PLAYER, GP20=1=AUX)

  SelectWheelState = 0
  PrevGP0=pin(GP0)
  VolumeWheelState = 0
  PrevGP1=pin(GP1)

  I2C2 OPEN 100, 100
  
  'Initialise variables when amplifier looses power - preserved during standby
  
  CurrentArtist = 0
  CurrentTrack = 0
  NumArtists=0
  CurrentVolume = 20      ' 20% (quiet)
  CurrentInputSource = 0  ' 0=MP3, 1=CD - also had 2=AUX but problem with relay :-(  
  RESTORE fontdata        ' Load the VFD display SC16315 segment fontdata array
  FOR ii = 32 TO 90
    READ VFDfont(ii)
  NEXT ii
  
  ' Get list of all artists from SD Card root folder
  dim string f$
  f$=DIR$("B:/*", DIR)
  do while f$<>"" and NumArtists<bound(artists$())
    artists$(NumArtists)=f$
    f$=DIR$()
    NumArtists=NumArtists+1
  loop
  Print str$(NumArtists) + " Artists found on disk"

  ArtistFinished=1  
  TrackTimer=0
  
ProgramStart:

  SETTICK 1000,TimerInterrupt,1

  print "Waiting power on.."
  
  'Note The main Amplifier CCT is de-powered at this time so cannot initialise anything!

  DO WHILE PIN(GP26) = 1 ' WAIT FOR POWER BUTTON TO BE PRESSED
  LOOP
  pin(gp15) = 1 'power on main amplifier hardware
  PAUSE 250
  DO WHILE PIN(GP26) = 0 ' WAIT FOR POWER BUTTON TO BE RELEASED
  LOOP

  pause 200 ' 200mS delay for the SC16315S VFD Driver and PT2259 volume control
  
  VolumeWheelState = 0
  SelectWheelState = 0
  InitVFD 
  PrintVFD(" RODYNE  26") ' init the display and display company/welcome message
  I2C2 WRITE &H44, 0, 1, &HF0 ' PT2259 volume control init/Reset/Clear registers
     print pin(gp14)
  SetVolume(CurrentVolume,0) 
     print pin(gp14)  

  pause 2000
  PrintVFD(" WELCOME  ") 
  SelectInput(CurrentInputSource,0) ' re-select correct input source 

  pause 1000
  pin(gp14) = 1 'turn on speakers
  

  DO ' NORMAL OPERATION LOOP (UNTIL POWER OFF/STBY BUTTON PRESSED)
  
    if ArtistFinished=1 then
      IF CurrentArtist<NumArtists then 
        GetTrackList "B:/"+artists$(CurrentArtist)+"/",0 'get selected artists songlist
        CurrentTrack=0  ' start at track 1
        Playtrack       ' and play song
      endif  
      ArtistFinished=0
      pause 500
    endif 
    
    if mm.info(sound)="OFF" then      ' No music playing (after init or track finished)
      print "Track finished"
      if CurrentTrack<NumTracks then  ' If more tracks then play the next one
        CurrentTrack=CurrentTrack+1   ' by incrementing the current track variable
        PlayTrack
      ELSE  
        CurrentArtist=CurrentArtist+1 ' if at end of tracklist then goto next artist
        ArtistFinished=1              ' will activate the code 10 lines above
      endif
      pause 500      
    endif    

    if pin(gp26) = 0 then exit DO ' Exit loop if POWER OFF BUTTON Pressed
    
    ' The volume and select wheels are rotary encoders, the wheelstates are 
    ' handled in the interrupts at the end of the code
    
    IF VolumeWheelState=2 then ' volume turned up
      if CurrentVolume<96 then
        CurrentVolume = CurrentVolume+4
        SetVolume(CurrentVolume,1)
      endif
      VolumeWheelState = 0
    endif  
    
    IF VolumeWheelState=1 then ' volume turned down
      if CurrentVolume>3 then
        CurrentVolume = CurrentVolume-4
        SetVolume(CurrentVolume,1)
      endif
      VolumeWheelState = 0
    endif  

    IF SelectWheelState=1 then 'Select wheel rotated anti-clockwise
      play STOP
      PrintVFD("PREVIOUS    ")
      if CurrentTrack>0 then
        print "PREV SONG"
        CurrentTrack=CurrentTrack-1
      else
        CurrentTrack=0  
      endif  
      Playtrack
      SelectWheelState = 0
      pause 500
    endif
    
    IF SelectWheelState=2 then ' Select wheel rotated clockwise
      play STOP
      PrintVFD("NEXT       ")
      if CurrentTrack<NumTracks then
        print "NEXT SONG"
        CurrentTrack=CurrentTrack+1
        Playtrack
      else
        ArtistFinished=1  
      endif  
      SelectWheelState = 0
      pause 500
    endif  
    
    ' Looking at the five buttons at the bottom left of the amplifier on Key3 input
    '
    ' +------------+------------+------------+------------+    +--------------+
    ' | Select MP3 | Select CD  | RND Track  | RND Artist |    | Pause/Resume |
    ' +------------+------------+------------+------------+    +--------------+
    '
    ' Get analog voltage of the Key3 input represents which button was pressed
    
    Key3 = pin(GP41) \ 100 ' \ is integer division : makes 0-4096 value = 0-41
    if Key3 <33 then ' KEY PRESSED
      pause 25
      Key3 = pin(GP41) \ 100 ' get value again as it can glitch      
      PRINT Key3 'debug
      if key3=9 then  ' Select MP3 (Jukebox) button pressed
        SelectInput(0,1)
        if mm.info(sound)="PAUSED MP3" then
          play resume
          pause 800
          PrintVFD("-RESUME-")          
        endif
      endif  
      if key3=14 then ' Select CD PLAYER button pressed
        SelectInput(1,1)
        if mm.info(sound)<>"OFF" then
          play pause
        endif
      endif  
      if key3=19 then ' RND Track button pressed
        CurrentTrack = INT(rnd*NumTracks) ' Select a random track for this artist
        PrintVFD("RND TRAK   ")
        play stop
        PlayTrack
      endif
      if key3=23 then ' RND Artist Button pressed
        CurrentArtist = INT(rnd*NumArtists) ' Select random artist
        PrintVFD("RND ARTS ")
        play stop
        ArtistFinished=1
      endif
      if key3=26 then ' Pause/resume Button pressed
        print mm.info(sound)
        if mm.info(sound)="PAUSED MP3" then ' Play is PAUSED so resume
          play resume
          PrintVFD("-RESUME-")
        else ' MP3 is playing so PAUSE
          PrintVFD("-PAUSED-")
          play pause
        endif        
      endif
      do
        pause 100 
      LOOP until pin(gp41)>33 ' Pause/debounce wait for user to release the switch
      DispPos=0 ' Causes re-display of song title after any key press
    endif

    ' Here we control what is displayed. When song starts display the artist/track
    ' info, note we can just use the track(currenttrack) as we dont have font data
    ' for slashes and backslashes so they appear as spaces.
    ' After we have displayed the track we display the song length counter in MM:SS
    ' format. Note the variable DispPos increments every second (see interrupt at 
    ' end of file) until reset, as does the song timer TrackMM (minutes) and 
    ' TrackSS (seconds) There is an initial 2 second delay before any of this 
    ' happens so we can display any button press info
    
    if mm.info(sound)="MP3" then 'Only do this when song playing
      if DispPos<>LastDP and DispPos>2 then ' only want to call once every second
        if DispPos<len(tracks$(CurrentTrack)) then ' display track info
          DispStr$=tracks$(CurrentTrack)
          DispStr$=MID$(DispStr$,2,LEN(DispStr$)-5)+"           "
          DispStr$=mid$(DispStr$,DispPos,8)+" "+STR$(CurrentTrack+1,2,0,"0")
        else ' display track timer
          DispStr$=str$(TrackMM,2,0,"0")+":"+STR$(TrackSS,2,0,"0")+"    "
          DispStr$=dispStr$+STR$(CurrentTrack+1,2,0,"0")
        endif
        PrintVFD(DispStr$)
        LastDP=DispPos
      endif
    endif  
  
  LOOP ' loops indefinately until the power/standby button pressed then we exit

  pin(gp14) = 0 'turn off speaker relays
  
  CurrentTrack=CurrentTrack-1 ' set pos back to start of song being played
  PrintVFD("           ")     ' otherwise when we pwr-on we get last display text
  
  ' was going to save the artist/track/volume to flash, but power consumption was
  ' only found to be 600mW in standby and 24W when on and playing at normal volume
  
  if mm.info(sound)<>"OFF" then ' STOP MP3 PLAYING
    play stop
  endif
  
  pin(gp15) = 0 'power off main amplifier hardware
  
  DO 
    pause 50
  LOOP UNTIL pin(gp26) <> 0 ' Wait for power button released
  pause 1000                ' Wait for sticky fingers

GOTO ProgramStart 'Program endless loop so loop back to just after initialise


'##########################################################################
'####    VFD FONT BITMAP DATA STARTS HERE ONLY ASCII 32 to ASCII 90    ####
'####    ARE REQUIRED AS WE CAN ONLY DO UPPERCASE LETTERS AND NUMBERS  ####
'####    (I THINK THIS IS THE WAY YOU ARE SUPPOSED TO DO CONSTS?)      ####
'##########################################################################

fontdata:
data &H0000 ' space (ASCII 32)
data &H0000 ' !
data &H0000 ' "
data &H0000 ' #
data &H0000 ' $
data &H0000 ' %
data &H0000 ' &
data &H0000 ' '
data &H0000 ' (
data &H0000 ' )
data &H0000 ' *
data &H0000 ' +
data &H0000 ' ,
data &H0300 ' -
data &H0001 ' .
data &H0000 ' /
data &HfC44 ' 0
data &H6000 ' 1
data &HDB00 ' 2
data &HF300 ' 3
data &H6700 ' 4
data &HB700 ' 5
data &HBF00 ' 6
data &HE000 ' 7
data &HFF00 ' 8
data &HE700 ' 9
data &H0003 ' :
data &H0003 ' ;
data &H0000 ' <
data &H0000 ' =
data &H0000 ' >
data &H0000 ' ?
data &H0000 ' @
data &HEE00 ' A
data &H9F48 ' B
data &H9C00 ' C
data &H7B00 ' D
data &H9F00 ' E
data &H8F00 ' F
data &HBD00 ' G
data &H6F00 ' H
data &H9090 ' I
data &HF800 ' J
data &H0E48 ' K
data &H1C00 ' L
data &H6C60 ' M
data &H6C28 ' N
data &HFC00 ' O
data &HCF00 ' P
data &HFC08 ' Q
data &HCC08 ' R
data &HB700 ' S
data &H8090 ' T
data &H7C00 ' U
data &H6028 ' V
data &H6C0C ' W
data &H006C ' X
data &H0070 ' Y
data &H9044 ' Z (ASCII 90)


'####################################
'#### INTERRUPT FUNCTIONS AT END ####
'####################################

SelectWheelInterrupt: ' Rotary encoder Falling edge triggered interrupt
  NewGP0 = pin(GP0)
  if NewGP0<>PrevGP0 THEN
    if pin(gp21) <> NewGP0 then
      SelectWheelState=1
    else
      SelectWheelState=2      
    endif    
    PrevGP0=NewGP0
  endif  
ireturn
   
VolumeWheelInterrupt: ' Rotary encoder Falling edge triggered interrupt
  NewGP1 = pin(GP1)
  if NewGP1<>PrevGP1 THEN
    if pin(gp13) <> NewGP1 then
      VolumeWheelState=1
    else
      VolumeWheelState=2    
    endif    
    PrevGP1=NewGP1
  endif
ireturn

TimerInterrupt:       ' track timer and position of scrolling VFD Display
  TrackSS=TrackSS+1
  if TrackSS>59 then  ' Seconds overflow so increment minutes
    TrackSS=0
    TrackMM=TrackMM+1 ' minutes unlikely to overflow unless MP3 > 99 minutes long 
  endif    
  DispPos=DispPos+1   ' scroll cursor to next
IRETURN