'Quadrature multichannel decoder for PicoMite using PIO
 
 'this is a 4 channel quadrature decoder for MMBasic V5.08.00 or newer
 'running on a PicoMite or PicoMiteVGA usinf PIO 1
 
 'Original PIO source: https://github.com/p-o-l-e/quadrature-decoder
 
 '30-4-2024  Volhout
 
 
 
 'system initialisation ---------------------------------------------------------
 
 'program PIO 1
 program_PIO 'program the code in PIO 1
 
 'quadrature decoders generic settings
 PIO_f%=63e6                            'frequency = 63MHz
 PIO_s%=0                               'shift register (shift in left)
 PIO_e%=PIO(execctrl gp0,wrp_tgt,wrap)  'start and stop of the loop
 
 'start quadrature decoders (uncomment the needed decoders)
 start_sm0 : sm0=1       'start decoder on GP0 and GP1
 'start_sm1 : sm1=1       'start decoder on GP2 and GP3
 'start_sm2 : sm2=1       'start decoder on GP4 and GP5
 'start_sm3 : sm3=1       'start decoder on GP26 and GP27
 
 
 
 'main MMBasic code -------------------------------------------------------------
 
 'this code is just a demo that shows the position of the quadrature decoders
 'the selected decoder positions are printed on the console
 'type "r" to reset the decoders to 0
 
 'main loop
 do
   a$=inkey$                                     'just for control
   
   'get the data from the fifo and print
   if sm0 then print str$(read_fifo(0),12,0);    'get data from decoder
   if sm1 then print str$(read_fifo(1),12,0);    'get data from decoder
   if sm2 then print str$(read_fifo(2),12,0);    'get data from decoder
   if sm3 then print str$(read_fifo(3),12,0);    'get data from decoder
   print
   
   'just some pause
   pause 100                                     'any delay needed
   
   'reset position (PIO X register) under control of keyboard
   if a$="r" then                                'press r to zero position
     if sm0 then pio execute 1,0,&hA023 '= assembly "mov X, null" (zero X reg)
     if sm1 then pio execute 1,1,&hA023 '= assembly "mov X, null" (zero X reg)
     if sm2 then pio execute 1,2,&hA023 '= assembly "mov X, null" (zero X reg)
     if sm3 then pio execute 1,3,&hA023 '= assembly "mov X, null" (zero X reg)
     a$=""
   end if
   
 loop while a$=""  'exit when any key not r
 
end
 
 
 
 
 ' subroutines -------------------------------------------------------------------

 
 'this function returns the actual count of decoder n
function read_fifo(n) as integer
 
 local dat%(3)
 pio read 1,n,4,dat%()                                   'read whole fifo
 read_fifo = dat%(3)                                    'last data in fifo
 if read_fifo>2147483647 then inc read_fifo,-4294967296 '2'th complement
 
end function
 
 
 'this subroutine programs the quadrature decoder program for PIO1 into
 'PIO program memory
sub program_PIO
 
 'this is the PIO program in machine code
 dim p%(7)=(&h001A00170015001A,&h0015001A001A0017,&h0017001A001A0015, &h001A00150017001A,&h4042A0404042A0C3,&hA029001A005AA0A6,&h8000A0C1A0290059,0)
 
 'here the program is programmed in memory
 pio program 1,p%()
 
 wrap=27           'end of the program
 wrp_tgt=16        'start of the program loop
 
end sub


 'this subroutine starts state machine 0 quadrature decoder on gp0 and gp1
sub start_sm0
 
 'uses GP0,GP1, assign pins in MMBasic
 setpin gp0,pio1
 setpin gp1,pio1
 
 'assign pins in PIO
 pin_sm0%=PIO(pinctrl 0,0,0,gp0)
 
 'configure and start PIO
 pio init machine 1,0,PIO_f%,pin_sm0%,PIO_e%,PIO_s%,wrp_tgt
 pio start 1,0
 
end sub

 
 'this subroutine starts state machine 1 quadrature decoder on gp2 and gp3
sub start_sm1
 
 'uses GP2,GP3, assign pins in MMBasic
 setpin gp2,pio1
 setpin gp3,pio1
 
 'assign pins in PIO
 pin_sm1%=PIO(pinctrl 0,0,0,gp2)
 
 'configure and start PIO
 pio init machine 1,1,PIO_f%,pin_sm1%,PIO_e%,PIO_s%,wrp_tgt
 pio start 1,1
 
end sub

 
 'this subroutine starts state machine 2 quadrature decoder on gp4 and gp5
sub start_sm2
 
 'uses GP4,GP5, assign pins in MMBasic
 setpin gp4,pio1
 setpin gp5,pio1
 
 'assign pins in PIO
 pin_sm2%=PIO(pinctrl 0,0,0,gp4)
 
 'configure and start PIO
 pio init machine 1,2,PIO_f%,pin_sm2%,PIO_e%,PIO_s%,wrp_tgt
 pio start 1,2
 
end sub

 
 'this subroutine starts state machine 3 quadrature decoder on gp26 and gp27
sub start_sm3
 
 'uses GP26,GP27, assign pins in MMBasic
 setpin gp26,pio1
 setpin gp27,pio1
 
 'assign pins in PIO
 pin_sm3%=PIO(pinctrl 0,0,0,gp26)
 
 'configure and start PIO
 pio init machine 1,3,PIO_f%,pin_sm3%,PIO_e%,PIO_s%,wrp_tgt
 pio start 1,3
 
end sub

Pre_load_value = [32bit INT]

Arm_the_PIO_index_latch

Move_the_motor_until_index_pulse_occurs

Transfer_Pre_load_value_to_PIO_count_register

   'set defined position in register X under control of the keyboard
   if a$="s" then
     input "desired count ";cnt%
     pio write 1,0,1,cnt%       'write the count cnt% in the fifo
     pio execute 1,0,&h8080  '= assemble "pull" (moves FIFO to OSR register)
     PIO execute 1,0,&hA027  '= assemble "mov X, OSR" moves the OSR value to X
     a$=""
   end if