[Altor Audio]

как-то так:

Код:

#define IN_1 TRISB1
#define IN_2 TRISB2
#define IN_3 TRISB3
#define IN_4 TRISB4
#define INP_1 RB1
#define INP_2 RB2
#define INP_3 RB3
#define INP_4 RB4
//----------------------------------------------
#define SEL_STATE (PORTB | (~0x1E)) // set all unused bits to 1
//----------------------------------------------

static void SetTris(u8 key){
  switch (key){
     case 0: IN_1=1;IN_2=1; IN_3=1;IN_4=1; break;
     case 1: IN_1=0;IN_2=1; IN_3=1;IN_4=1; break;
     case 2: IN_1=1;IN_2=0; IN_3=1;IN_4=1; break;
     case 3: IN_1=1;IN_2=1; IN_3=0;IN_4=1; break;
     case 4: IN_1=1;IN_2=1; IN_3=1;IN_4=0; break;
  }
}

//----------------------------------------------------------------
void sel_init(void){  // call once at the program start
   INP_1 =0; INP_2 =0; INP_3 =0; INP_4 =0;   // set port bits to 0 forever
//
   sel=1;                           // set input 1 at the start
   // sel=ReadEE(LastInputAddress); //  or read the last value from EEPROM
//
   S_data_send(sel-1); // установка мультиплексора
   SetTris(sel); // set dedicated pin as output=0;
}
//----------------------------------------------------------------
void selector(void){   // call periodically (from timer interrupt or main loop)
static unsigned char selstate;
unsigned char currentstate, newsel=0;


SetTris(0); // set all pins as inputs
currentstate=SEL_STATE;

if(currentstate!=0xFF){
     if (selstate != currentstate)) {
            selstate = currentstate;
            
            if(!INP_1) newsel++; else
            if(!INP_2) newsel++; else
            if(!INP_3) newsel++; else
            if(!INP_4) newsel++;
            
            if(newsel &&(newsel!=sel)){
               sel=newsel;    // sel and newsel = 1,2,3,4
               S_data_send(sel-1); // установка мультиплексора
            }
     }
}
SetTris(sel); // set dedicated pin as output=0;
}