AVR Programming 2

AVR Programming 2 Robotix, IIT Kharagpur

C Programming : Macros ● #define <identifier> <replacement token list> ● Replaces identifier with replacement token ● Example: #define Var_X 100 would replace Var_X anywhere in the programme with the value 100 ● #define RADTODEG(x) ((x) * 57.29578) : Converts radians to degrees. If there is RADTODEG(20) anywhere in the prgramme it will be replaced by 20 * 57.29578

Checkbit ● A bit can be either 0 or 1

● We check whether the bit is 0 or not. ● var X=PINB; var Y=X & (1<<BIT) //Value of bit is in Y ● Checking the 4rd Bit. The And function returns an non zero binary number. Thus if a bit is 0 it returns 0.

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● Checking the 3rd Bit. The And function returns 0. Thus if a bit is 0 it returns 0. ● #define CHECK_BIT(var,pos) ((var) & (1<<(pos)))

Clearbit ● Clears the bit or sets it to 0. ● var X=PINB; var X=X & ~(1<<BIT); ● #define CLEAR_BIT(var,pos) ((var) & ~(1<<(pos))) ● Following changes 4th bit to 0. Rest remaining same.

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Setbit ● Sets the bit or sets it to 1. ● var X=PINB; var X=X | (1<<BIT); ● #define SET_BIT(var, pos) ((var) | (1<<(pos))) ● Following changes 4th bit to 1. Rest remaining same.

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Toggle Bit ● Uses XOR Operator ● XOR returns one only when only 1 of the two inputs is 1. ● Thus if a bit is 0 it becomes 1 and if its one it becomes 0. XOR with 0 ● var X=PINB; var X=X ^ (1<<BIT); 0 1 0 0 0 1 1 0 XOR 0

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