Serial mouse data manipulation

[kevin5059]

Hi, I'm doing a project with using a serial mouse to control the frequency and volume of the sound that emit from the speaker. However, I faced with a hard problem with my C programming sicne I'm new in this field. I got some data format about the serial mouse from this website:

http://www.cs.net/lucid/mouse.htm

For your information, I'm using the serial mouse that work at 1200 baud with 1 stop bit and no parity. At the end, I try to developed my own C codes to read the data from the mouse and display it to the screen. However, the data are not as what I expected.

Here are my C code:

[green]
#include <dos.h>
#include <stdio.h>
#include <string.h>
#include <beck.h>[/green]
[blue]/*beck.h is self-created header file*/[/blue]
[green]
#define  Byte1_Mask     0x40
#define  Left_Mask      0x20
#define  Right_Mask     0x10

#define  Waiting_For_Byte1     0     /*0100 0000*/
#define  Waiting_For_Byte2     1     /*0010 0000*/
#define  Waiting_For_Byte3     2     /*0001 0000*/

#define  Mou_Write_Latch        0x202
#define  Mou_Read_Latch         0x201
#define  Mou_Control_Latch      0x200
#define  Speaker                0x308

#define   Status_Register       1
#define   Data_Register         2
#define   Mouse_IRQ             3
#define   Delay                 50      	
[/green]
int x=0;
int y=0;
char Byte1,Byte2,Byte3;
signed char dx,dy;
int Mouse_State=Waiting_For_Byte1;
int Ready=0;
int s=0;
int Left_Button=0;
int Right_Button=0;

[blue]/*interrupt service routine- get the 3 bytes from the mouse and manipulate into Byte1, Byte2 and Byte3*/[/blue]
void interrupt Mouse_Interrupt(void)
{
      char ch;
      ch=Mouse_Read(Data_Register);
      [blue]/*Mouse_Read is a service funtion in beck.h*/
      /*It is used to read the 8 bits data from the serial mouse*/[/blue]

   switch(Mouse_State)
   {
   	case Waiting_For_Byte1:
      	if(ch & Byte1_Mask)
         [blue]/*check for the first byte*/[/blue]
         {
         	Byte1=ch;
            Left_Button = ((ch & Left_Mask)>>5);
            Right_Button= ((ch & Right_Mask)>>4);
            Mouse_State=Waiting_For_Byte2;
         }
         break;
      case Waiting_For_Byte2:
      	Byte2=ch;
         Mouse_State= Waiting_For_Byte3;
         break;
      case Waiting_For_Byte3:
      	Byte3=ch;
         dx = (signed char)(((Byte1 & 0x03)<<6) |(Byte2 & 0x3F));
         dy = (signed char)(((Byte1 & 0x0C)<<4) |(Byte3 & 0x3F));
         Mouse_State=Waiting_For_Byte1;
         Ready=1;
         break;
    }
}

[blue]/*setup the hardware interrupt*/[/blue]
void Mouse_On(void)
{
	Enable_int(Mouse_IRQ);
   [blue]/*Enable the interrupt at Line 3 or Mouse_IRQ*/[/blue]
   Install_ISR(Mouse_IRQ,1,Mouse_Interrupt);
   [blue]/*assign the Mouse_Interrupt function as the interrupt service routine*/[/blue]
   Mouse_Write(Status_Register, 0x30);
   [blue]/*set bit 4 and bit 5 of status register*/[\blue]
}

[blue]/*remove the hardware interrupt*/[/blue]
void Mouse_Off(void)
{
	Remove_ISR(Mouse_IRQ);
   [blue]/*disable the interrupt at line 3*/[/blue]
}

int main(void)
{
   unsigned int Frequency =1000;
   unsigned int Volume=1000;

   Mouse_On();
   [blue]/*setup hardware interrupt*/[/blue]

   do
   {
   	if(Ready==1)
      {
      	Ready=0;
         Frequency=Frequency+dx;
         Volume= Volume+dy;

         printf("dx=%d\n",dx);
         printf("dy=%d\n",dy);
         printf("Left Button=%d\n",Left_Button);
         printf("Right Button=%d\n",Right_Button);

         printf("Frequency=%d\n",Frequency);
         printf("Volume=%d\n",Volume);
         printf("\n");
       }
   }while(!Key_Pressed());

   Mouse_Off();
   [blue]/*remove hardware interrupt*/[/blue]
   Set_Stdio_Focus(SHELL_FOCUS);
   return 0;
}
[blue]/*End of main program*/[/blue]

The values of dx and dy should become positive when the mouse is moving rightward and upward, but this program keep on sending me a negative value and cause my Frequency and Volume down to negative value. I'm very new in C language, someone who know it please give me your hand. Thank you!!!

 

[xwb]

A mouse range of +/- 128 seems rather small. Are you sure about the dx/dy computation? Try changing them to short or int in the declaration.

 

[kevin5059]

Yes xwb, the mouse range is from +127 to -128, that why I declared my dx/dy as char(8 bits). For the dx/dy computation, I think that should be no problem since I got this manipulation code from the web and just made some modification. A question is, why do I need to change my declaration to short or int?? short (16 bits) and int ( 32 bits ) which is not relevant to my purpose rite??? Anyway, i'm not very sure about this. Please give me some guide.Thank.