'create a AR88 WW2 receiver with coarse and fine dial, driven from a
 'quadrature encoder
 'the quadrature decoder runs on PIO
 'the fine dial is driven by a stepper motor (must rotate multi turns)
 'the coarse dial is driven from a servo (180 degrees max)
 'send strings to main RP (text t.b.d)
 
 'hardware : 64*64 stepper = 4096 per revolution
 'hardware : 125*4 quadrature encoder = 500 per revolution
 'softwaare gain needed = 4096/500 = 8
 
 
 
 'stepper driver
 Option default integer
 
 'system initialisation -------------------------------------------------------
 
 'inti the stepper control pins
 initio
 
 ' variables for stepper
 Dim phases(7)=(&b0001,&b0011,&b0010,&b0110,&b0100,&b1100,&b1000,&b1001)
 Dim steps2go=0, quadra,quadra_old, delta, limh
 
 'stepper motor can make 1000 steps per second max. In a 20ms loop equals
 limh = 1000 * 0.02
 
 'set the max speed of the stepper at 1ms per step (1kHz)
 SetTick 1,step_it
 
 'variable for servo
 dim positio!,rot=1

 
 'program PIO 1
 program_PIO 'program the code in PIO 1
 
 'start quadrature decoders (uncomment the needed decoders)
 start_sm0 'start decoder on GP7 and GP8
 zero_sm0  'zero quadrature
 
 
 
 'main program loop --------------------------------------------------------
 
 Do
   'INPUT read PIO FIFO for quadrature changes
   quadra = -read_fifo(0)
   
   'debug
   'print str$(quadra,12,0)   'get data from decoder

   
   'OUTPUT to stepper
   'add delta fifo since last read to stes2go (pos or neg)
   delta=quadra_old-quadra:quadra_old=quadra
   
   'limit the pulse speed to the max the stepper can handle to avoid lag
   delta = max(min(delta*8,limh),-limh)       '8 = software gain
   
   'output the value
   if rot then Inc steps2go,delta else steps2go=0


   'OUTPUT to SERVO : add delta fifo to servo pos
   'PWM 3,50,(position_as_a_percentage * 0.05 + 5)
   positio! = 7.5 + 0.0025 * quadra : rot=1
   if positio!<3 then positio!=3 : rot=0       'hardware limit
   if positio!>11.5 then positio!=11.5 :rot=0  'hardware limit
   PWM 3,50,positio!

   
   'OUTPUT send delta to UART
   print #1,str$(quadra,6,0)   'get data from decoder
   
   Pause 20  'loop speed
 Loop While Inkey$=""
 
 PIO stop 1,0
 PIO clear 1
 
End
 
 
 
 ' subroutines ---------------------------------------------------------------
 
 'zero counter state machine 0
Sub zero_sm0
 
 PIO execute 1,0,&hA023 '= assembly "mov X, null" (zero X reg)
 
End Sub
 
 
 '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 gp12 and gp13
Sub start_sm0
 
 'uses GP12,GP13, assign pins in MMBasic
 SetPin gp7,pio1
 SetPin gp8,pio1
 
 '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
 
 'assign pins in PIO
 pin_sm0%=Pio(pinctrl 0,0,0,gp7)
 
 '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
 
 'inits stepper output signals on GP2...5
Sub initio
 local brightness=75         'default 75% (3/4 of 4S lipo)
 
 'init stepper pins to dout and low
 For i=2 To 5
   SetPin "GP"+Str$(i),dout :Pin("gP"+Str$(i))=0
 Next
 
 'use PWM3A f=to drive a servo
 setpin gp6,PWM
 PWM 3,50,7.5    'mid position
 
 'use PWM7A/B to dim light bulbs
 setpin gp14,pwm
 setpin gp15,pwm
 pwm 7,1000,100-brightness,100-brightness   'inverted output = 100%-brightness
 
 setpin gp1,gp0,com1
 open "COM1:115200" as #1
 
End Sub
 
 
 'moves the stepper until step2go is zero
Sub step_it
 Static ps=0
 Local dn
 
 If steps2go<>0 Then
   Inc steps2go,Choice(steps2go<0,1,-1)
   dn=Choice(steps2go<0,7,1)
   Inc ps,dn:ps=ps Mod 8
   Port(GP2,4)=phases(ps)
 End If
 
End Sub