The FFT Library is a computational library for Renesas MCUs.

FFT (Fast Fourier Transform) is a fast algorithm for implementing discrete Fourier transform. This FFT library also uses assembler tuning to realize highly efficient processing for Renesas MCUs.

The FFT enables the user to measure the frequency characteristics of the input data. For example, by executing the FFT on voice data, you can measure the amplitude (volume) of each frequency that comprises the sound.

Release Information


Latest Ver.: V.1.00 Release 01

Released: May 20, 2014

Details of upgrade (See Tool News)

Operating Environment

How to Obtain

Provide Conditions

Application Examples

power spectrum analysis, sensor data analysis, noise analysis


  • High-speed processing with assembler tuning
  • Memory savings
  • Simple APIs
  • Excellent development efficiency when paired with Renesas tools


The following list shows the functions supported by the FFT library and processing times when operating an RX600 Series MCU at 100MHz.

Function Processing Time
Function Name Actual number / Complex number No. of points No. of cycles (cycles) Actual time (µsec)
R_cfft16 Complex number 16 994 9.94
R_cfft32 Complex number 32 3597 35.97
R_cfft64 Complex number 64 6928 69.28
R_rfft128 Actual number 128 12695 126.95
R_rfft256 Actual number 256 28826 288.26
R_rfft512 Actual number 512 63588 635.88
R_rfft1024 Actual number 1024 141038 1410.38


  • FFT Library
  • Sample Program
  • User's Manual

Operating Environment

Renesas offers the following evaluation environments to ensure immediate use of the FFT library.

Target MCU Evaluation Environment Debugger
RL78 Family Integrated development environment CS+ Simulator for CS+ of RL78 Family, 78K0R and 78K0
IAR Embedded Workbench for Renesas RL78 Note1 IAR C-SPY Debugger for RL78


  1. by IAR Systems

How to Obtain


Provide Conditions

Evaluation Version
We provide the evaluation version as a sample code for customers adopting Renesas microcontrollers. You can download the sample code from here. In addition, we do not offer any technical supports for the evaluation version. Please use it with reference to the attached user's manual to the sample code.
Commercial version
This item is not available in the Commercial version.

Target Devices

RL78 Family Note1


  1. Only the evaluation versions available.

The DSP Library includes a function of FFT Library for RX600 Series. The evaluation version of FFT Library for RL78 Family can be downloaded from here.

Development Tools Support

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