From: robertapengelly@gmail.com   
      
   On Monday, 13 November 2023 at 09:01:29 UTC, wolfgang kern wrote:   
   > On 13/11/2023 09:49, Robert Pengelly wrote:   
   > > On Monday, 13 November 2023 at 08:37:18 UTC, wolfgang kern wrote:   
   > ...   
   > >> I found my hand written notes from 1980 on Serial Mice now,   
   > >> two button standard:   
   > >> 1200 baud, No Parity, 7(or8)bit, 1 stop bit   
   > >> 1st byte   
   > >> 7 * don't care   
   > >> 6 == 1 sync bit   
   > >> 5 Right Button Down   
   > >> 4 Left Button Down   
   > >> 3 b7 Y   
   > >> 2 b6 Y   
   > >> 1 b7 X   
   > >> 0 b6 X   
   > >> 2nd byte   
   > >> 7 *   
   > >> 6 == 0   
   > >> 5..0 b5..0 X   
   > >> 3rd byte   
   > >> 7 *   
   > >> 6 ==0   
   > >> 5..0 b5..0 Y   
   > >> assume BX points to buffer yet   
   > >>>>> mov cl, [bx + 2]   
   > >> AND CL, 0x7f ;can't be sure for b7==0   
   > >> ;missed to sign extend AX,AL   
   > >> CBW makes AX sign extended from AL   
   > >> or ax, cx OK insert low 6 bits   
   > >>   
   > >> ADD [mouse_y],AX it does a SUB if AX is negativ   
   > >> mov cl, [bx + 1]   
   > >> AND CX,0x7f   
   > >> MOV AL,DL   
   > >> CBW   
   > >> OR AX,CX   
   > >> ADD [mouse_x],AX   
   > >> DONE:   
   > ...   
   > > Just as I was going to reply you sent that last message. Anyways this   
   seems to work:   
   > >   
   > > xor ax, ax   
   > > xor dx, dx   
   > > xor cx, cx   
   > > mov bx, offset buffer   
   > >   
   > > mov al, [bx]   
   > > and al, HEX (0C)   
   > >   
   > > mov cl, 4   
   > > shl ax, cl   
   > >   
   > > cbw   
   > >   
   > > mov cl, [bx + 2]   
   > > or ax, cx   
   > > add [mouse_y], ax   
   > >   
   > > mov al, [bx]   
   > > and al, HEX (03)   
   > >   
   > > mov cl, 6   
   > > shl ax, cl   
   > >   
   > > cbw   
   > >   
   > > mov cl, [bx + 1]   
   > > or ax, cx   
   > > add [mouse_x], ax   
   > >   
   > > but not sure if it's right or not. You did just have "CBW makes AX sign   
   extended from AL" so maybe the code is right.   
   > Fine so far, you rely on b7=0 in first byte which may cause errors.   
   > you could check of the first byte got a sync bit to avoid jumping mice.   
   > __   
   > wolfgang   
   I'm a little confused by :   
      
   you rely on b7=0 in first byte which may cause errors.   
   you could check of the first byte got a sync bit to avoid jumping mice.   
      
   You had:   
      
   1st byte   
   7 * don't care   
   6 == 1 sync bit   
   5 Right Button Down   
   4 Left Button Down   
   3 b7 Y   
   2 b6 Y   
   1 b7 X   
   0 b6 X   
      
   in your previous message, do you mean bit 6 (i.e. the sync bit).  If you do   
   should I do something like:   
      
   test al, 0x40   
   jnz .done   
      
   before the updating code   
      
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