/* Reflow Oven Controller
*
* Copyright (C) 2021  Mario Hüttel <mario.huettel@gmx.net>
*
* This file is part of the Reflow Oven Controller Project.
*
* The reflow oven controller is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License version 2 as
* published by the Free Software Foundation.
*
* The Reflow Oven Control Firmware is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with the reflow oven controller project.
* If not, see <http://www.gnu.org/licenses/>.
*/

#include <reflow-controller/fir-filter.h>

void fir_filter_init_null(struct fir_filter_fixed *filter)
{
	uint32_t idx;

	if (!filter)
		return;
	filter->put_idx = 0U;
	for (idx = 0; idx < filter->tap_count; idx++)
		filter->data = 0;
}


int32_t fir_filter_process_sample(struct fir_filter_fixed *filter, int32_t sample)
{
	uint32_t tap_idx;
	uint32_t coeff_idx;
	int32_t output = 0;

	if (!filter)
		return 0;

	/* Store the new data point */
	filter->data[filter->put_idx] = sample;

	coeff_idx = filter->put_idx;

	/* Apply fir taps on data */
	for (tap_idx = 0; tap_idx < filter->tap_count; tap_idx++) {
		output += filter->data[tap_idx] * filter->coefficients[coeff_idx];

		if (coeff_idx)
			coeff_idx--;
		else
			coeff_idx = filter->tap_count-1;
	}

	filter->put_idx++;
	if (filter->put_idx >= filter->tap_count)
		filter->put_idx = 0;

	return output;
}