PIC Microcontoller DSP Math Methods

• 24bit 256 step IIR filter by Tony Kübek
• FFT
• Averageing 16 by Andrew Warren
• Averageing 16 by Dmitry
• Averageing 256 by Andrew Warren
• Median Filter and Sort by Mehmet Çetin
• uLaw to 16bit linear
• Scott Dattalo Tweaking a PIC for twist
• Novel method of generating a sinewave without a lookup table. Code is in the old Parallax/SX menomics, but those are easily translated to MPASM. +

see also:

• PIC Microcontoller Audio Input / Output
• Piclist post 2000/11/10/132825a "Fourier calc for tone detection" by Scott Dattalo
• http://www.edtn.com/embapps/emba057.htm Digital Frequency Synthesis
• For C code out put see Tony Fishers digital filter code generator

Archive:

• PICList post "FIR code" 16bit Averaging by 16 +
• PICList post "Challenge: FIR Filter on an 18f series device" +
• PICList post "What is IIR filter(long)" Tutorial on DSP
• PICList post "Averaging Algorithm" Nice overview of IIR and FIR
• PICList post "Digital filtering on PIC's ?" Compairison of FIR and IIR filters
• PICList post "Audio Spectrum Analizer" Using IIR and FIR in place of FFT
• PICList post "Sine table" Using FIR filters as DFT
• PICList post "Don't use Microchip's FFT" (see Robert Lacostes' PICSPECT instead)
• PICList post "help ... running average in pic asm/ 16 bit numbers?"
• PICList post "Median and Mean filtering"
• PICList post "Sort algorithm ?" Median Filtering
• PICList post "Choosing the IIR coefficients. was PIC (dF/dt Gradient slew)"
• PICList post "Choosing the IIR coefficients. was PIC (dF/dt Gradient slew)"
• PICList post "What is IIR filter?"
• PICList post "standard algorithm?" Low pass filtering

See also:

• Good book on the subject: Advanced Digital Signal Processing
• Design Idea: "8-bit microcontroller implements digital lowpass filter" by Abel Raynus (in HTML) (in pdf format) is a relatively gentle introduction to the "simple averaging" filters. (Dmitry and Andrew Warren have built super-optimized PIC assembly versions of this filter, linked to elsewhere on this page).

  Raynus starts with the deceptively simple formula Y[n] = X[n]*a + Y[n-1]*b and eventually translates it to the equivalent Y[n] = Y[n-1] + (X[n]-Y[n-1])/F which an assembly-language programmer can make super-fast when F is a power of 2, X is one byte, and Y is 2 bytes (as Dmitry and Warren's code shows).

  (Raynus uses a Freescale processor, but points out that the principles work for just about every kind of microcontroller -- since this page is for PIC-specific filters, is there some other page that would be more appropriate for filters in general?).

Questions:

• TakeThisOuTtonino_compasSPAM at @spam@hotmail.com asks: " Does anyone have a good PID code (assembly, not C) for 8-bit PIC (eg PIC16F877 or PIC16F616)?" +
• TakeThisOuTdoyinjinSPAM at @spam@yahoo.com asks:

  pls how can i use a pic 16f876 to receive and store at least 16 voice prints based on isolated word recognition(open,close) to a 24lc04 eeprom ; then receive other voice inputs, compare them with the stored voice prints.On recognition of any of these voice prints, the PIC sends a signal and controls a dc servomotor either in the forward or reverse direction.

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