'PIO clear
pio clear 1
dim d%=0

print "write"
 
for i=1 to 4
   pio write 1,0,1,d%
next i

print "ready"

end

   if(piointerrupt){  // have any PIO interrupts been set
#ifndef PICOMITEVGA
       for(int pio=0 ;pio<2;pio++){
#else
       for(int pio=1 ;pio<2;pio++){
#endif
           PIO pioinuse=(pio==0 ? pio0 :pio1);
           for(int sm=0;sm<4;sm++){
               int TXlevel=((pioinuse->flevel)>>(sm*4)) & 0xf;
               int RXlevel=((pioinuse->flevel)>>(sm*4+4)) & 0xf;
               if(RXlevel && pioRXinterrupts[sm][pio]){  //is there a character in the buffer and has an interrupt been set?
                   intaddr=pioRXinterrupts[sm][pio];
                   goto GotAnInterrupt;
               }
               if(TXlevel !=4 && pioTXlast[sm][pio]==4 && pioTXinterrupts[sm][pio]){  // was the buffer full last time and not now and is an interrupt set?
                   intaddr=pioTXinterrupts[sm][pio];
                   pioTXlast[sm][pio]=TXlevel;
                   goto GotAnInterrupt;
               }
               pioTXlast[sm][pio]=TXlevel;
           }
       }
   }

' demo program to deomnstrate the use of the PIO interrupt
' the PIO is programmed to push 1 word into FIFO at every rising edge of the GP0 pin.
' the GP0 pin is controlled from MMBasic in this demo, but could also be driven from
' an external source.
 
'-------------------------------- PIO state machine -----------------------------------

'PIO clear
 pio clear 1
 
'the PIO program
'address    code    mnemonics         comment
'  0      2000      WAIT GP0=0
'  1      2080      WAIT GP0=1
'  2      8000      PUSH noblock
'  3      0000      JMP 0
 
'program pio1
 pio program line 1,0,&h2000
 pio program line 1,1,&h2080
 pio program line 1,2,&h8000
 PIO program line 1,3,&h0000
 
'write the configuration, running 100kHz (data in FIFO 10us after rising edge GP0)
 PIO init machine 1,0,1e5,0,,,0



'-------------------------------- MMBasic MAIN ---------------------------------------
 
'Halt the PIO from GP0 from MMBasic before it fills the FIFO out of control
 setpin gp0,dout
 pin(gp0)=0
 
'variables
 dim d%
 dim newdata%=0
 
'start the pio1 code, state machine 1.0 will be waiting for a rising edge on the GP0 pin
'then it will push 1 word into fifo. Then it will wait for the falling edge. The cycle repeats.
 PIO start 1,0
 
'interrupt format PIO INTERRUPT PIO,SM,RX_SUB,TX_SUB
 PIO interrupt 1,0,GetFifo,OFF
 
'freguently feed data into the fifo
 Settick 100,FeedFifo
 
'Main: check if data, when yes, then print
 do
   if newdata%=1 then
     print d%
     newdata%=0
   end if
 loop



'----------------------------------- SUBS ---------------------------------------
 
'in this sub get get 1 word from the Fifo. We can expand that to read data until
'the fifo is empty by repeated read and check of the fifo empty flag.
SUB GetFifo
 PIO READ 1,0,1,d%
 newdata%=1
end sub
 
'in this sub we toggle the GP0 pin to force the PIO to put data in the FIFO
sub FeedFifo
 pin(gp0)=1:pause 1:pin(gp0)=0:pause 1
end sub