'step/dir_decoder_pico_PIO_version 4

'program options
do_assemble=0        'either assemble the code, or brute force program
use_test_signal=1    'internally generate test signal

'step pulse generation for testing
if use_test_signal then
  stp_init             'init GPIO pins
  settick 10,do_step   '10ms = 100Hz step frequency
  cntr = 0            'step counter
  direction = 0       '0 = count up, 1 = count down  
else
  setpin gp0,pio1    'the STEP signal
  setpin gp1,pio1    'the DIRECTION signal
end if


'Generic defines
f= 63e6             '63 MHz PIO frequency
pio clear 1
dim dat%(4)         'array to store FIFO data


' PIO code -------------------------------------------------------------------

if do_assemble then 'assemble
 
  'header and start of the PIO code
  pio assemble 1,".program test"
  pio assemble 1,".line 0"
 
  'wait for step pulse
  pio assemble 1,"wait 0,pin,0"  'wait for GP0 to become 0
  pio assemble 1,"wait 1,pin,0"  'wait for GP0 to become 1 = rising edge STEP pulse
  pio assemble 1,"JMP pin, plus1" 'jump according state GP1 pin
 
  'The plus and minus routines, X is the actual 32 bit position counter
  pio assemble 1,"minus1:"      'label:jump here to decrement X
  pio assemble 1,"JMP X--, push_out"  'decrement X
  pio assemble 1,"JMP push_out" 'regardless X value go to push_out
  pio assemble 1,"plus1:"       'label to increment X
  pio assemble 1,"mov X, !X"    'invert X
  pio assemble 1,"JMP X--, next1" 'decrement x
  pio assemble 1,"next1:"        'label:regardless X value come here
  pio assemble 1,"mov X, !X"     'invert back
 
  'send the most recent position to FIFO
  pio assemble 1,"push_out:"      'label
  pio assemble 1,"mov ISR, X"     'move X to ISR
  pio assemble 1,"push"           'push ISR into FIFO, not blocked
 
  'jump to start of PIO program
  pio assemble 1,"JMP 0"          'jump to beginning
 
  pio assemble 1,".end program"       '50900RC4 and newerr
  'pio assemble 1,".end program list" 'needed for 50900RC3
 
else  'brute force program the same code
 
  dim p%(7)=(&h4800c520a02020,&ha0290047a0290008,&h8000a0c1,0,0,0,0,0)
  pio program 1,p%()
 
end if


'configure PIO 1 statemachine 0 (PIO 1 is free on PicoMiteVGA)
p0=pio(pinctrl 0,0,0,gp0)           'gp0 is lowest IN pin (gp0,gp1)
e0=pio(execctrl gp1,0,31)           'GP1=dir, wrap and wrap target
s0=pio(shiftctrl 0,0,0,0,0,0)       'shift IN direction is left (the 5'th '0')


'initialize PIO 1 state machine 0
pio init machine 1,0,f,p0,e0,s0,0)  'init machine @ start loop


'start the quadrature decoder PIO 1 statemachine 0
pio start 1,0



'main MMBasic code -------------------------------------------------------------

'main loop
do
  a$=inkey$                                     'just for control
 
  'get the data from the fifo
  pio read 1,0,5,dat%()                         'read whole fifo
  posi%=dat%(4)                                  'last data in fifo
  if posi%>2147483647 then inc posi%,-4294967296 '2'th complement
  print posi%                                    'show position
 
  'just some pause
  pause 100                                     'any delay needed
 
  'reset position (PIO X register) under control of keyboard
  if a$="r" then                                'press r to zero position
    pio execute 1,0,&hA023    '= assembly "mov X, null" (zero the X register)
    a$=""
  end if
 
  'set defined position in register X under control of the keyboard
  if a$="s" then
    input "desired count ";cnt%
    cnt%=cnt% and &hffffffff
    pio write 1,0,1,cnt%       'write the count cnt% in the fifo
    pio execute 1,0,&h8080  '= assemble "pull" (moves FIFO to OSR register)
    PIO execute 1,0,&hA027  '= assemble "mov X, OSR" moves the OSR value to X
    a$=""
  end if
 
loop while a$=""  'exit when any key not r

end



'test code in MMBasic that drives GP0 and GP1 according
sub stp_init
setpin gp0,dout : pin(gp0)=0  'step pin
setpin gp1,dout : pin(gp1)=0  'dir pin
end sub

sub do_step
'this rountine counts 1000 steps up, then down, etc...
inc cntr,1            'new step
pulse gp0,0.1         '1 ms step pulse
if cntr>=1000 then
  cntr = 0
  direction = 1 - direction
  pin(gp1) = direction
end if
end sub