lut-generator

This repo contains a multipurpose Look Up Table generator. It is oriented to microcontrollers world where runtime computation is something you may want to avoid when generating signal samples. This tool generates the sampled signal in the form of an array which can be copy-pasted directly in the microcontroller script. There is also a gnuplot-based display functionality

A number of built-in wave forms are avalaible:

• straight line
• sine
• cosine
• square
• triangle
• amplitude modulation

Requirements

• A C++11 compatible compiler
• GNU make
• Gnuplot (only for the graphic part)

Installation

To install type make all from within the project folder. The code has been tested successfully with GCC 4.8.4 under Ubuntu 14.04 but, due to the use of the functions std::stof and std::stoi which are bugged in MinGW, it will throw compilation errors if compiled in Windows enviroment. A VS version will come, sooner o later...

Usage

When executed the program reads the parameters from the configuration file config.conf, e.g.

signal_amplitude = 5
signal_samples = 500
signal_type = sine
dac_bit_size = 12

where

• signal_amplitude is the maximum amplitude of the wave form, which ranges from 0 to this value. Default is 1.
• signal_samples the number of samplings of the LUT. Default is 100.
• signal_type selects the wave form, pick one from line sine cosine square triangle am. Default is line.
• dac_bit_size is the number of bits used by the Digital To Analog converter to store the amplitude range.

Output

A number of files are generated:

• lut.scale displays the amplitude bin in terms of the DAC bit representation.
• lut.dat contains the sampled signal in amplitude scale and DAC scale, used by gnuplot script.
• lut.gp contains the auto-generated gnuplot script to create the plot.
• lut.out contains a report of the parameters used and also the LUT in decimal, hex and binary format.
• lut.png image with the plots of the signal contained in lut.dat.

Mathematical Note

The code is open source so feel free to modify it according to your needs. If you want to add your own wave form remind that the logic of the program requires that you use a mathematical representation of it which ranges from 0 to 1 and is periodic with period 1.

Programming Note

For what concern the amplitude modulation wave form the default parameters are

• omega = 25 the carrier period
• modulation = 0.5 the modulation parameter

These values are hard-coded, as preprocessor definitions, into the program so you need to modify them inside lutg.cpp.