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Accessing individual PORT bits in AVR with avrgcc (winAVR)

In some compilers like codevisonAVR you can access individual bits using PINA.0 or PORTA.2, to do a similar thing with avrgcc you can use


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// structure to allow bit field operations, name conversions: PORTA.0 -> PORT_A.b0  PORTB.7 -> PORT_B.b7
typedef struct{ uint8_t b0:1;
                uint8_t b1:1;
                uint8_t b2:1;
                uint8_t b3:1;
                uint8_t b4:1;
                uint8_t b5:1;
                uint8_t b6:1;
                uint8_t b7:1; } bits;
 
// define all the ports of your microcontroller, add more ports depending on the available mcu ports
#define PORT_A (* (volatile bits *) &PORTA)
#define PIN_A (* (volatile bits *) &PINA)
#define DDR_A (* (volatile bits *) &DDRA)
 
#define PORT_B (* (volatile bits *) &PORTB)
#define PIN_B (* (volatile bits *) &PINB)
#define DDR_B (* (volatile bits *) &DDRB)
 
// then you can use specific bits like this to write or read specific bits
PORT_A.b0=1;   // write value to PORTA bit 0
PIN_B.b4=0;   // write value to PINB bit 4



A better way and faster is to use these macro

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// add this defines
#define SETBIT(ADDRESS,BIT) (ADDRESS |= (1<<BIT)) 
#define CLEARBIT(ADDRESS,BIT) (ADDRESS &= ~(1<<BIT)) 
#define FLIPBIT(ADDRESS,BIT) (ADDRESS ^= (1<<BIT)) 
#define CHECKBIT(ADDRESS,BIT) (ADDRESS & (1<<BIT)) 
#define WRITEBIT(RADDRESS,RBIT,WADDRESS,WBIT) (CHECKBIT(RADDRESS,RBIT) ? SETBIT(WADDRESS,WBIT) : CLEARBIT(WADDRESS,WBIT))
 
// and then you can use
SETBIT(PORTX,2);  // set bit2 of portx (set to 1)
SETBIT(PORTY,0);  // set bit0 of porty
 
CLEARBIT(PORTX,5); // clear bit5 of portx (set to 0)
 
FLIPBIT(PORTX,2);  // invert bit2 of portX, if it was 1 it becomes 0, and if 0 becomes 1
                    // example for portx 0x10101010 the result is 0x10101110
                    
if (CHECKBIT(PORTX,4)) {} else {} // result is true if bit4 of portx is 1, false if it is 0
if (!CHECKBIT(PORTX,4)) {} else {} // result is true if bit4 of portx is 0, false if it is 1
 
 
WRITEBIT(PORTX,0,PORTY,2);   // copy the bit0 of portx to bit2 of porty



And the third way are these two macros defined in sfr_defs.h

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if(bit_is_set(PINC,0))   //this can check if a bit is 1
if(bit_is_clear(PINC,0))  // this can check if a bit is 0



Alex

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