'--------------------------------------------------------------------------------------
' real time measurement of preignition angle for two stroke engine
' made by Zsolt Fazekas (fazekaszs at hotmail.com)
' Copyright reserved
'--------------------------------------------------------------------------------------
 
$regfile = "89s52.dat"
$crystal = 22118400
$map
$baud = 19200
 
Dim E As Word                                                 'time elapsed from interruption until upper dead point
Dim F As Word                                                 'time elapsed from upper dead point until interruption
Dim K As Byte                                                 'secondary variable counting the number of measures made by timer2
 
Dim Fh As Byte                                                'Fh, Fl, Eh, El - upper and lower bytes of F and E
Dim Fl As Byte
Dim Eh As Byte
Dim El As Byte
 
Reset F
Reset E
Reset K
 
Reset Fh
Reset Fl
Reset Eh
Reset El
 
Set Tcon.0                                                    'INT0 falling edge
Set Tcon.2                                                    'INT1 falling edge
 
Enable Interrupts
Enable Timer2
Enable Timer1
Disable Serial
 
 
Config Timer2 = Counter , Gate = Internal , Mode = 0          'not the capture mode, however simple counter mode
Counter2 = 0                                                  'reset counter (driven by a 200KHz outside clock sign coming in through port P1.0)
 
Config Timer1 = Timer , Gate = Internal , Mode = 2            'auto reload for transmit
Load Timer1 , 3
 
Declare Sub Kuld(f As Word , E As Word , Fh As Byte , Fl As Byte , Eh As Byte , El As Byte)
 
On Int0 Fordulatszam                                          'falling edge interrupt coming in through port P3.2 (at upper dead point)
On Int1 Elogyujtas                                            'falling edge interrupt coming in through port P3.3 (at the point of ignition)
 
Start Timer1
Start Timer2
 
 
Do
Enable Int0
Enable Int1
Loop
End
 
Fordulatszam:                                                 'INT0 interrupt, saving E 
Stop Timer2                                                   'stop timer 2 for reading
Reset Tcon.1                                                  'deleting the interrupt flag
K = K + 1
 
If T2con.7 = 1 Then                                           'overflow flag is 1, (f. e. because crankshaft halts)
Counter2 = 0
Reset T2con.7                                                 'overflow flag is deleted
Start Timer2
F = 0
E = 0
K = 0
Else
   Eh = Th2
   El = Tl2
   E = Makeint(el , Eh)
         If K >= 3 Then                                       'after enabling interrupt one has to wait until K=3
         Disable Int0
         Disable Int1
         Call Kuld
         K = 0                                                'the value of K is reset after serial transmission
         End If
   Counter2 = 0
   Start Timer2
End If
Return
 
 
Sub Kuld(f As Word , E As Word , Fh As Byte , Fl As Byte , Eh As Byte , El As Byte)
F = F + 6                                                     '6 and 4: time ellapsing between stopping and starting Timer2
E = E + 4                                                     'this should be added to times measured for correction
Fh = High(f)
Fl = Low(f)
Eh = High(e)
El = Low(e)
If Fl = 255 And Fh = 255 Then                                 'the higest value should be avoided because of sincronisation
Fl = 254
End If
If El = 255 And Eh = 255 Then                                 'the higest value should be avouded because of sincronisation
El = 254
End If
If P2.1 = 1 Then                                              'switch
Scon = &H40
Enable Serial
Sbuf = 255                                                    'for sincronisation
Bitwait Scon.1 , Set
Reset Scon.1
Sbuf = 255                                                    'for sincronisation
Bitwait Scon.1 , Set
Reset Scon.1
Sbuf = Fl
Bitwait Scon.1 , Set
Reset Scon.1
Sbuf = Fh
Bitwait Scon.1 , Set
Reset Scon.1
Sbuf = El
Bitwait Scon.1 , Set
Reset Scon.1
Sbuf = Eh
Bitwait Scon.1 , Set
Reset Scon.1
Disable Serial
End If
End Sub
 
 
Elogyujtas:                                                   'INT1 interrupt, saving F
Stop Timer2                                                   'stop timer 2 for reading
Reset Tcon.3                                                  'deleting the interrupt flag
K = K + 1
 
If T2con.7 = 1 Then                                           'overflow flag is 1, (f. e. because crankshaft halts)
Counter2 = 0
Reset T2con.7                                                 'overflow flag is deleted
Start Timer2
K = 0
E = 0
F = 0
Else
      Fh = Th2
      Fl = Tl2
      F = Makeint(fl , Fh)
      Counter2 = 0
      Start Timer2
End If
Return