PX4-Autopilot/src/drivers/distance_sensor/tfmini/tfmini_parser.cpp

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/**
 * @file modified from sf0x_parser.cpp
 * @author Lorenz Meier <lm@inf.ethz.ch>
 * @author Chuong Nguyen <chnguye7@asu.edu>
 * @author Ayush Gaud <ayush.gaud@gmail.com>
 *
 * Declarations of parser for the Benewake TFmini laser rangefinder series
 */

#include "tfmini_parser.h"
#include <string.h>
#include <stdlib.h>

// #define TFMINI_DEBUG

#ifdef TFMINI_DEBUG
#include <stdio.h>

const char *parser_state[] = {
	"0_UNSYNC",
	"1_SYNC_1",
	"2_SYNC_2",
	"3_GOT_DIST_L",
	"4_GOT_DIST_H",
	"5_GOT_STRENGTH_L",
	"6_GOT_STRENGTH_H",
	"7_GOT_PRESERVED",
	"8_GOT_QUALITY",
	"9_GOT_CHECKSUM"
};
#endif

int tfmini_parse(char c, char *parserbuf, unsigned *parserbuf_index, TFMINI_PARSE_STATE *state, float *dist)
{
	int ret = -1;
	//char *end;

	switch (*state) {
	case TFMINI_PARSE_STATE::STATE6_GOT_CHECKSUM:
		if (c == 'Y') {
			*state = TFMINI_PARSE_STATE::STATE1_SYNC_1;
			parserbuf[*parserbuf_index] = c;
			(*parserbuf_index)++;

		} else {
			*state = TFMINI_PARSE_STATE::STATE0_UNSYNC;
		}

		break;

	case TFMINI_PARSE_STATE::STATE0_UNSYNC:
		if (c == 'Y') {
			*state = TFMINI_PARSE_STATE::STATE1_SYNC_1;
			parserbuf[*parserbuf_index] = c;
			(*parserbuf_index)++;
		}

		break;

	case TFMINI_PARSE_STATE::STATE1_SYNC_1:
		if (c == 'Y') {
			*state = TFMINI_PARSE_STATE::STATE1_SYNC_2;
			parserbuf[*parserbuf_index] = c;
			(*parserbuf_index)++;

		} else {
			*state = TFMINI_PARSE_STATE::STATE0_UNSYNC;
			*parserbuf_index = 0;
		}

		break;

	case TFMINI_PARSE_STATE::STATE1_SYNC_2:
		*state = TFMINI_PARSE_STATE::STATE2_GOT_DIST_L;
		parserbuf[*parserbuf_index] = c;
		(*parserbuf_index)++;

		break;

	case TFMINI_PARSE_STATE::STATE2_GOT_DIST_L:
		*state = TFMINI_PARSE_STATE::STATE2_GOT_DIST_H;
		parserbuf[*parserbuf_index] = c;
		(*parserbuf_index)++;

		break;

	case TFMINI_PARSE_STATE::STATE2_GOT_DIST_H:
		*state = TFMINI_PARSE_STATE::STATE3_GOT_STRENGTH_L;
		parserbuf[*parserbuf_index] = c;
		(*parserbuf_index)++;

		break;

	case TFMINI_PARSE_STATE::STATE3_GOT_STRENGTH_L:
		*state = TFMINI_PARSE_STATE::STATE3_GOT_STRENGTH_H;
		parserbuf[*parserbuf_index] = c;
		(*parserbuf_index)++;

		break;

	case TFMINI_PARSE_STATE::STATE3_GOT_STRENGTH_H:
		*state = TFMINI_PARSE_STATE::STATE4_GOT_RESERVED;
		parserbuf[*parserbuf_index] = c;
		(*parserbuf_index)++;

		break;

	case TFMINI_PARSE_STATE::STATE4_GOT_RESERVED:
		*state = TFMINI_PARSE_STATE::STATE5_GOT_QUALITY;
		parserbuf[*parserbuf_index] = c;
		(*parserbuf_index)++;

		break;

	case TFMINI_PARSE_STATE::STATE5_GOT_QUALITY:
		// Find the checksum
		unsigned char cksm = 0;

		for (int i = 0; i < 8; i++) {
			cksm += parserbuf[i];
		}

		if (c == cksm) {
			parserbuf[*parserbuf_index] = '\0';
			unsigned int t1 = parserbuf[2];
			unsigned int t2 = parserbuf[3];
			t2 <<= 8;
			t2 += t1;

			if (t2 < 0xFFFFu) {
				*dist = ((float)t2) / 100;
			}

			*state = TFMINI_PARSE_STATE::STATE6_GOT_CHECKSUM;
			*parserbuf_index = 0;
			ret = 0;

		} else {
			*state = TFMINI_PARSE_STATE::STATE0_UNSYNC;
			*parserbuf_index = 0;
		}

		break;
	}

#ifdef TFMINI_DEBUG
	printf("state: TFMINI_PARSE_STATE%s\n", parser_state[*state]);
#endif

	return ret;
}