Embedded Programming Tips and Tricks

Fast Division

On microcontrollers without a divide instruction very fast division can be done by bit shifting a variable right. Each shift does a divide by two.

For example Y = Y >> 1 Will result in a divide by 2 or X = X >> 4 Will result in a divide by 16

By adding a multiplication you can achieve other, more complex, divisions.

For example Z = Z * 3; Z = Z >> 4; (div 16)

Will result in a division of 5.33 (16/3 = 5.33)

Be sure to do the multiply first, otherwise bits will be lost. Also be sure the variable size is large enough to store the multiplied value.