avr_common_macros.h

/*
 * Common bit handling macros for AVR (avr-gcc)
 *
 * Examples:
 *
 * #define LED_DIR BITP(DDRB, PB4) // LED_DIR is "variable" pointing to single bit (PB4) in DDRB
 * #define LED_STATE BITP(PORTB, PB4) // LED_STATE points to single bit (PB4) in PORTB
 * LED_DIR = DIR_OUT; // Set pin as output
 * LED_STATE = LEVEL_HIGH; // Switch LED on
 * 
 * BITS_SET(DDRB, PB3, PB5, PB7); // Set bits PB3, PB5 and PB7 in DDRB, leave other bits untouched.
 * BITS_SET_EX(DDRB, PB7); // Sets only PB7 in DDRB, other bits are zeroed (set exclusive).
 * BITS_CLEAR(PORTB, PB4); // Clear bit PB4 in PORTB, leave other bits untouched.
 * BITS_FLIP(PORTB, PB2, PB3, PB7); // Flip bits PB2, PB3 and PB7 in PORTB, leave other bits untouched.
 */

/*
 * Struct to handle bits in registers
 */
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;
} bitmask_s;

/*
 * Helper macros for bit pointer macro
 */
#define BNAME(x) BSTR(x)
#define BSTR(x) b##x

/*
 * Bit pointer macro which can be used to make individual
 * bit variables
 */
#define BITP(var, bit) ((volatile bitmask_s*)&var)->BNAME(bit)

/*
 * Bit-Shift-Or macros for 1-8 parameters 
 */
#define BSO_(a,b,c,d,e,f,g,h,...) (0xFF & (1<<(a) | 1<<(b) | 1<<(c) | 1<<(d) | 1<<(e) | 1<<(f) | 1<<(g) | 1<<(h)))
#define BSO(...) BSO_(__VA_ARGS__,8,8,8,8,8,8,8,8)

/* 
 * Macros to set, clear and flip multiple bits in registers
 */
#define BITS_SET(x, ...) x |= BSO(__VA_ARGS__)
#define BITS_CLEAR(x, ...) x &= ~BSO(__VA_ARGS__)
#define BITS_SET_EX(x, ...) x = BSO(__VA_ARGS__)
#define BITS_FLIP(x, ...) x ^= BSO(__VA_ARGS__)

/*
 * Common defines
 */
#define DIR_OUT 1
#define DIR_IN 0
#define LEVEL_HIGH 1
#define LEVEL_LOW 0