' midiRec3v02.bas

' Ring buffer setup (4096 entries for bytes and timestamps)
Dim rb_byte%(4095)
Dim rb_time%(4095)
Dim rb_head% = 0
Dim rb_tail% = 0

' Open the serial interface using a 1-byte interrupt trigger!
SetPin GP4, GP5, COM2
Open "COM2:31250, 4096, midiin, 1" As #2
Open "temp.bin" For RANDOM As #3  

' Flash-Init dummy start
Dim dummy%(7)
For i% = 0 To 7: dummy%(i%) = 0: Next i%
Memory PRINT #3, 8, dummy%()

' OPTIMISATION: Micro-burst buffer (only 32 events = 256 bytes)
Dim buffer%(31)
Dim idx% = 0

Dim st% = 0, rs% = 0
Dim dat1% = 0, exp% = 0
Dim t_evt% = 0
Dim run_flag% = 0

' Variables for loop reception
Dim b% = 0
Dim t_incoming% = 0

Print Chr$(27)+"[2J"+Chr$(27)+"[H"
CLS
Print "midiRec3v02 Ready (Micro-Burst Mode)..."
Timer = 0

Do
 If LCASE$(Inkey$) = "s" Then Exit Do

' Check whether the ring buffer contains any new data'
 If rb_head% = rb_tail% Then Continue Do

' Retrieve a byte and a precise timestamp from the ring buffer
 b% = rb_byte%(rb_tail%)
 t_incoming% = rb_time%(rb_tail%)
 rb_tail% = (rb_tail% + 1) Mod 4096

 If b% >= &HF8 Then Continue Do

 If b% >= &HF0 And b% <= &HF7 Then
   rs% = 0
   If b% = &HF0 Then st% = 3
   If b% = &HF7 Then st% = 0
   Continue Do
 EndIf
 If st% = 3 And b% < &H80 Then Continue Do

 ' Status-Byte
 If b% >= &H80 Then
   rs% = b%
   st% = 1
   run_flag% = 0
   t_evt% = t_incoming%
   
   Select Case (b% And &HF0)
     Case &HC0, &HD0: exp% = 1
     Case Else :      exp% = 2
   End Select
   Continue Do
 EndIf

 If rs% = 0 Then Continue Do

 If st% = 1 Then
   If run_flag% = 1 Then
     t_evt% = t_incoming%
     run_flag% = 0
   EndIf
   
   dat1% = b%
   
   If exp% = 1 Then
     buffer%(idx%) = t_evt% Or (rs% << 32) Or (dat1% << 40)
     idx% = idx% + 1
     st% = 1
     run_flag% = 1
   Else
     st% = 2
   EndIf

 ElseIf st% = 2 Then
   buffer%(idx%) = t_evt% Or (rs% << 32) Or (dat1% << 40) Or (b% << 48)
   idx% = idx% + 1
   st% = 1
   run_flag% = 1
 EndIf

' MICRO-BURST WRITE: Write as few as 32 events (256 bytes)!
 If idx% = 32 Then
   Memory PRINT #3, 256, buffer%()
   idx% = 0
 EndIf
Loop

Close #2

' Run the remaining data in the ring buffer through the state machine in its entirety'
Do While rb_head% <> rb_tail%
 b% = rb_byte%(rb_tail%)
 t_incoming% = rb_time%(rb_tail%)
 rb_tail% = (rb_tail% + 1) Mod 4096
 
 If b% >= &HF8 Then Continue Do
 If b% >= &HF0 And b% <= &HF7 Then
   rs% = 0
   If b% = &HF0 Then st% = 3
   If b% = &HF7 Then st% = 0
   Continue Do
 EndIf
 If st% = 3 And b% < &H80 Then Continue Do

 If b% >= &H80 Then
   rs% = b%
   st% = 1
   run_flag% = 0
   t_evt% = t_incoming%
   Select Case (b% And &HF0)
     Case &HC0, &HD0: exp% = 1
     Case Else :      exp% = 2
   End Select
   Continue Do
 EndIf

 If rs% = 0 Then Continue Do

 If st% = 1 Then
   If run_flag% = 1 Then
     t_evt% = t_incoming%
     run_flag% = 0
   EndIf
   dat1% = b%
   If exp% = 1 Then
     buffer%(idx%) = t_evt% Or (rs% << 32) Or (dat1% << 40)
     idx% = idx% + 1
     st% = 1
     run_flag% = 1
   Else
     st% = 2
   EndIf
 ElseIf st% = 2 Then
   buffer%(idx%) = t_evt% Or (rs% << 32) Or (dat1% << 40) Or (b% << 48)
   idx% = idx% + 1
   st% = 1
   run_flag% = 1
 EndIf
 
 If idx% = 32 Then
   Memory PRINT #3, 256, buffer%()
   idx% = 0
 EndIf
Loop

' Write the remaining events to the event buffer
If idx% > 0 Then
 Memory PRINT #3, idx% * 8, buffer%()
EndIf

Close #3
Print "Saved temp.bin"
End

SUB midiin
 Local t%
 Local b_in%
 Local next_head%
 
 Do While Loc(#2) > 0
   t% = Fix(Timer) And &HFFFFFFFF
   b_in% = Asc(Input$(1, #2))
   next_head% = (rb_head% + 1) Mod 4096
   
   If next_head% <> rb_tail% Then
     rb_byte%(rb_head%) = b_in%
     rb_time%(rb_head%) = t%
     rb_head% = next_head%
   EndIf
 Loop
END SUB