PWL of PWM Pulses

pwmcalc.cpp

#include <iostream>
#include <iomanip>
#include <string>
#include <fstream>

#define RISE_FALL_TIME 1e-9
#define LOW 0.0
#define HIGH 3.3

#define MAX(a,b) ((a) > (b)) ? (a) : (b)

const unsigned int BITS_MAX_VAL[] = {0, 2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048, 4096, 8192, 16384, 32768, 65536};

using namespace std;

double produce_pwl_single(const double period, const int resolution, const unsigned int value, double offset, ostream &out = cout){
	// Writes a single 'pulse' to the output stream
	// returns the end time of the pulse
	double now = offset;

	out << setprecision(10) << now << "\t" << setprecision(5) <<  LOW << endl;
	
	if(value > 0){
		
		double duration_of_on_pulse = ((double) value / BITS_MAX_VAL[resolution]) * period;

		if(duration_of_on_pulse > (2 * RISE_FALL_TIME)){
			now += RISE_FALL_TIME;
			out << setprecision(10) << now << "\t" << setprecision(5) << HIGH  << endl;

			now += duration_of_on_pulse;
			out << setprecision(10) << now << "\t" << setprecision(5) << HIGH  << endl;
			
			// LOW
			now += RISE_FALL_TIME;
			out << setprecision(10) << now << "\t" << setprecision(5) << LOW  << endl;
		}
	}
	return MAX(now, (offset + period));
}


float pwl_from_lut(fstream &in, const float frequency, const int resolution, const string file_path, const int update_period, ostream &out = cout){
	string line;
	float period_start_time = 0.f;
	double period = 1.0 / frequency;
	while(getline(in, line)){
		
		// Don't use atoi here - actually catch and handle exceptions!
		try{
			const unsigned int value = static_cast<unsigned int>(stoi(line));
			if(value < 0 || value > BITS_MAX_VAL[resolution]){
				cerr << "Invalid value in LUT: " << line << endl;
				return -1.f;
			}
			for(int i = 0; i < update_period; i++){
				period_start_time = produce_pwl_single(period, resolution, value, period_start_time, out);
			}
		}
		catch(const invalid_argument& arg_ex){
			cerr << "Invalid value in LUT: " << line << endl;
			return -1.f;
		}
	}
	return period_start_time;
}

int main(int argc, char** argv){

	// frequency, resolution (bits), value or LUT, update period
	if(argc < 4){
		cerr << "Usage:\n" 
			<< argv[0] << " FREQUENCY RESOLUTION VALUE/ LUT [UPDATE PERIOD]\n\n"
			<< "FREQUENCY\t\t\t PWM Frequency in Hz\n"
			<< "RESOLUTION\t\t\t PWM Resolution in bits\n"
			<< "VALUE / LUT\t\t\t PWM Value (int) or path to a LUT of values\n"
			<< "UPDATE PERIOD (Only for LUT)\t If using a LUT, number of PWM pulses before updating the value" << endl;

	return 1;
	}

	const float pwm_freq = atof(argv[1]);
	if(pwm_freq <= 0){ 
		cerr << "Invalid value for frequency: " << argv[1] << endl;
		return 1;
	}

	const int pwm_res = atoi(argv[2]);
	if(pwm_res <= 0){ 
		cerr << "Invalid value for resolution: " << argv[1] << endl;
		return 1;
	}

	const string file_path_or_value(argv[3]);
	try{
		const unsigned int value = static_cast<unsigned int>(stoi(file_path_or_value));
		double period = 1.0 / pwm_freq;
		auto success = produce_pwl_single(period, pwm_res, 0.0, value);
		if(success <= 0){
			return 1;
		}
		return 0;

	}
	catch(const invalid_argument& arg_ex){

		fstream file_in(file_path_or_value);
		if(!file_in.is_open()){
			cerr << "Could not open: " << file_path_or_value << endl;
			return -1.f;
		}

		if(argc < 5){
			cerr << "No update period supplied for use with LUT file" << endl;
			return 1;
		}

		int update_period = atoi(argv[4]);
		if(update_period <= 0){
			cerr << "Invalid update period: " << argv[4] << endl;
			return 1;
		}

		auto success = pwl_from_lut(file_in, pwm_freq, pwm_res, file_path_or_value, update_period);
		if(success <= 0){
			return 1;
		}
		return 0;
	}
	return 1;
}