PIC Microcontroller Basic Math Square Root Methods

• 32 bit integer by Andy David and Scott Dattalo Calculates the square root of a thirty-two bit number using the binary restoring method. Takes between 392 and 439 cycles (incl. call and return). for the 17c43. (only uses rotates, subtracts, and compares -- no multiplies or divides).
• 24 bit floating point by Nikolai Golovchenko . See also IEEE to/from Microchip format conversion
• 24 bit integer by Andy David and Scott Dattalo
• 16 bit successive approximation by Andy David, for the 17c43
• 16 bit integer for the 18Cxxx by Scott Dattalo( 108 cycles max )
• 16 bit integer for dsPIC/PIC24 by Isaac Marino Bavaresco
• 12 bit by Nikolai Golovchenko
• 8 bit by Nikolai Golovchenko
• 8 bit fast by Nikolai Golovchenko
• 8 bit small and fast by Nikolai Golovchenko idea from Scott Dattalo tweak by Dmitry Kiryashov

see also:

• http://www.dattalo.com/technical/software/pic/picsqrt.html
• http://www.dattalo.com/technical/theory/sqrt.html
• Microchip forum: "faster sqrt()" with assembly source code for the PIC 18f452 that implements "digit by digit calculation" (which only uses rotates, subtracts, and compares -- no multiplies or divides).
• "Microchip app note TB040: Fast Integer Square Root" by Ross M. Fosler gives code for a sqrt() routine for the PIC18Cxx2. (Uses the hardware multiplier in the PIC18Cxx2). This sqrt() routine returns the 16 bit result for a 32 bit integer X in 1002 cycles (max). If the top 2 bytes are zero (it's a 16 bit integer X), this sqrt() returns the byte result in 149 cycles (max). After this was written, the above much faster routines were developed.

See also:

• /techref/method/math/sqrt.htm square root theory and algorithms

Just for once, i'd like to take the square root of a negative number and have it turn out to be okay.

Questions:

• jnandakumar at TakeThisOuTidlind.com asks: " I am looking for a square root routine for 16F series. 24bit & above. Can any body help me please" +

Archive:

• PICList post "square roots for the 18F" +

32-bit signed integer math routines. add, subtract, multiply, divide, round, sqrt, bin2dec, dec2bin. By Peter Hemsley. +

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