Started following some tutorial on att85 usi. Downloaded example code from make avr book.

Make AVR Examples/setupProject/macros.h

@@ -0,0 +1,26 @@
+
+/* Standard Macros */
+/* You can totally get by without these, but why? */
+
+/* Make sure we've already got io / sfr / pindefs loaded */
+#ifndef   _AVR_IO_H_
+#include  <avr/io.h>
+#endif
+
+/* Reminder: the following useful bit-twiddling macros are
+   always included in avr/sfr_defs.h, which is called from
+   avr/io.h 
+
+ bit_is_set(sfr, bit)
+ bit_is_clear(sfr, bit)
+ loop_until_bit_is_set(sfr, bit)
+ loop_until_bit_is_clear(sfr, bit)
+
+*/
+
+/* Define up the full complement of bit-twiddling macros */
+#define BV(bit)               (1 << bit)
+#define set_bit(sfr, bit)     (_SFR_BYTE(sfr) |= BV(bit))  // old sbi()
+#define clear_bit(sfr, bit)   (_SFR_BYTE(sfr) &= ~BV(bit)) // old cbi()
+#define toggle_bit(sfr, bit)  (_SFR_BYTE(sfr) ^= BV(bit))  
+