libsigrok/hardware/common/dmm/rs9lcd.c

/*
 * This file is part of the libsigrok project.
 *
 * Copyright (C) 2012 Alexandru Gagniuc <mr.nuke.me@gmail.com>
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/*
 * RadioShack 22-812 protocol parser.
 *
 * This protocol is currently encountered on the RadioShack 22-812 DMM.
 * It is a 9-byte packet representing a 1:1 mapping of the LCD segments, hence
 * the name rs9lcd.
 *
 * The chip is a bare die covered by a plastic blob. It is unclear if this chip
 * and protocol is used on any other device.
 */

#include <string.h>
#include <ctype.h>
#include <math.h>
#include <glib.h>
#include "libsigrok.h"
#include "libsigrok-internal.h"

#define LOG_PREFIX "rs9lcd"

/* Byte 1 of the packet, and the modes it represents */
#define IND1_HZ		(1 << 7)
#define IND1_OHM	(1 << 6)
#define IND1_KILO	(1 << 5)
#define IND1_MEGA	(1 << 4)
#define IND1_FARAD	(1 << 3)
#define IND1_AMP	(1 << 2)
#define IND1_VOLT	(1 << 1)
#define IND1_MILI	(1 << 0)
/* Byte 2 of the packet, and the modes it represents */
#define IND2_MICRO	(1 << 7)
#define IND2_NANO	(1 << 6)
#define IND2_DBM	(1 << 5)
#define IND2_SEC	(1 << 4)
#define IND2_DUTY	(1 << 3)
#define IND2_HFE	(1 << 2)
#define IND2_REL	(1 << 1)
#define IND2_MIN	(1 << 0)
/* Byte 7 of the packet, and the modes it represents */
#define INFO_BEEP	(1 << 7)
#define INFO_DIODE	(1 << 6)
#define INFO_BAT	(1 << 5)
#define INFO_HOLD	(1 << 4)
#define INFO_NEG	(1 << 3)
#define INFO_AC		(1 << 2)
#define INFO_RS232	(1 << 1)
#define INFO_AUTO	(1 << 0)
/* Instead of a decimal point, digit 4 carries the MAX flag */
#define DIG4_MAX	(1 << 3)
/* Mask to remove the decimal point from a digit */
#define DP_MASK		(1 << 3)

/* What the LCD values represent */
#define LCD_0		0xd7
#define LCD_1		0x50
#define LCD_2		0xb5
#define LCD_3		0xf1
#define LCD_4		0x72
#define LCD_5		0xe3
#define LCD_6		0xe7
#define LCD_7		0x51
#define LCD_8		0xf7
#define LCD_9		0xf3

#define LCD_C		0x87
#define LCD_E
#define LCD_F
#define LCD_h		0x66
#define LCD_H		0x76
#define LCD_I
#define LCD_n
#define LCD_P		0x37
#define LCD_r

enum {
	MODE_DC_V	= 0,
	MODE_AC_V	= 1,
	MODE_DC_UA	= 2,
	MODE_DC_MA	= 3,
	MODE_DC_A 	= 4,
	MODE_AC_UA	= 5,
	MODE_AC_MA	= 6,
	MODE_AC_A	= 7,
	MODE_OHM	= 8,
	MODE_FARAD	= 9,
	MODE_HZ		= 10,
	MODE_VOLT_HZ	= 11,	/* Dial set to V, Hz selected by Hz button */
	MODE_AMP_HZ	= 12,	/* Dial set to A, Hz selected by Hz button */
	MODE_DUTY	= 13,
	MODE_VOLT_DUTY	= 14,	/* Dial set to V, duty cycle selected */
	MODE_AMP_DUTY	= 15,	/* Dial set to A, duty cycle selected */
	MODE_WIDTH	= 16,
	MODE_VOLT_WIDTH	= 17,	/* Dial set to V, pulse width selected */
	MODE_AMP_WIDTH	= 18,	/* Dial set to A, pulse width selected */
	MODE_DIODE	= 19,
	MODE_CONT	= 20,
	MODE_HFE	= 21,
	MODE_LOGIC	= 22,
	MODE_DBM	= 23,
	/* MODE_EF	= 24, */ /* Not encountered on any DMM */
	MODE_TEMP	= 25,
	MODE_INVALID	= 26,
};

enum {
	READ_ALL,
	READ_TEMP,
};

struct rs9lcd_packet {
	uint8_t mode;
	uint8_t indicatrix1;
	uint8_t indicatrix2;
	uint8_t digit4;
	uint8_t digit3;
	uint8_t digit2;
	uint8_t digit1;
	uint8_t info;
	uint8_t checksum;
};

static gboolean checksum_valid(const struct rs9lcd_packet *rs_packet)
{
	uint8_t *raw;
	uint8_t sum = 0;
	int i;

	raw = (void *)rs_packet;

	for (i = 0; i < RS9LCD_PACKET_SIZE - 1; i++)
		sum += raw[i];

	/* This is just a funky constant added to the checksum. */
	sum += 57;
	sum -= rs_packet->checksum;
	return (sum == 0);
}

static gboolean selection_good(const struct rs9lcd_packet *rs_packet)
{
	int count;

	/* Does the packet have more than one multiplier? */
	count = 0;
	count += (rs_packet->indicatrix1 & IND1_KILO)  ? 1 : 0;
	count += (rs_packet->indicatrix1 & IND1_MEGA)  ? 1 : 0;
	count += (rs_packet->indicatrix1 & IND1_MILI)  ? 1 : 0;
	count += (rs_packet->indicatrix2 & IND2_MICRO) ? 1 : 0;
	count += (rs_packet->indicatrix2 & IND2_NANO)  ? 1 : 0;
	if (count > 1) {
		sr_dbg("More than one multiplier detected in packet.");
		return FALSE;
	}

	/* Does the packet "measure" more than one type of value? */
	count = 0;
	count += (rs_packet->indicatrix1 & IND1_HZ)    ? 1 : 0;
	count += (rs_packet->indicatrix1 & IND1_OHM)   ? 1 : 0;
	count += (rs_packet->indicatrix1 & IND1_FARAD) ? 1 : 0;
	count += (rs_packet->indicatrix1 & IND1_AMP)   ? 1 : 0;
	count += (rs_packet->indicatrix1 & IND1_VOLT)  ? 1 : 0;
	count += (rs_packet->indicatrix2 & IND2_DBM)   ? 1 : 0;
	count += (rs_packet->indicatrix2 & IND2_SEC)   ? 1 : 0;
	count += (rs_packet->indicatrix2 & IND2_DUTY)  ? 1 : 0;
	count += (rs_packet->indicatrix2 & IND2_HFE)   ? 1 : 0;
	if (count > 1) {
		sr_dbg("More than one measurement type detected in packet.");
		return FALSE;
	}

	return TRUE;
}

/*
 * Since the 22-812 does not identify itself in any way, shape, or form,
 * we really don't know for sure who is sending the data. We must use every
 * possible check to filter out bad packets, especially since detection of the
 * 22-812 depends on how well we can filter the packets.
 */
SR_PRIV gboolean sr_rs9lcd_packet_valid(const uint8_t *buf)
{
	const struct rs9lcd_packet *rs_packet = (void *)buf;

	/*
	 * Check for valid mode first, before calculating the checksum. No
	 * point calculating the checksum, if we know we'll reject the packet.
	 */
	if (!(rs_packet->mode < MODE_INVALID))
		return FALSE;

	if (!checksum_valid(rs_packet)) {
		sr_spew("Packet with invalid checksum. Discarding.");
		return FALSE;
	}

	if (!selection_good(rs_packet)) {
		sr_spew("Packet with invalid selection bits. Discarding.");
		return FALSE;
	}

	return TRUE;
}

static uint8_t decode_digit(uint8_t raw_digit)
{
	/* Take out the decimal point, so we can use a simple switch(). */
	raw_digit &= ~DP_MASK;

	switch (raw_digit) {
	case 0x00:
	case LCD_0:
		return 0;
	case LCD_1:
		return 1;
	case LCD_2:
		return 2;
	case LCD_3:
		return 3;
	case LCD_4:
		return 4;
	case LCD_5:
		return 5;
	case LCD_6:
		return 6;
	case LCD_7:
		return 7;
	case LCD_8:
		return 8;
	case LCD_9:
		return 9;
	default:
		sr_dbg("Invalid digit byte: 0x%02x.", raw_digit);
		return 0xff;
	}
}

static double lcd_to_double(const struct rs9lcd_packet *rs_packet, int type)
{
	double rawval = 0, multiplier = 1;
	uint8_t digit, raw_digit;
	gboolean dp_reached = FALSE;
	int i, end;

	/* end = 1: Don't parse last digit. end = 0: Parse all digits. */
	end = (type == READ_TEMP) ? 1 : 0;

	/* We have 4 digits, and we start from the most significant. */
	for (i = 3; i >= end; i--) {
		raw_digit = *(&(rs_packet->digit4) + i);
		digit = decode_digit(raw_digit);
		if (digit == 0xff) {
			rawval = NAN;
			break;
		}
		/*
		 * Digit 1 does not have a decimal point. Instead, the decimal
		 * point is used to indicate MAX, so we must avoid testing it.
		 */
		if ((i < 3) && (raw_digit & DP_MASK))
			dp_reached = TRUE;
		if (dp_reached)
			multiplier /= 10;
		rawval = rawval * 10 + digit;
	}
	rawval *= multiplier;
	if (rs_packet->info & INFO_NEG)
		rawval *= -1;

	/* See if we need to multiply our raw value by anything. */
	if (rs_packet->indicatrix1 & IND2_NANO)
		rawval *= 1E-9;
	else if (rs_packet->indicatrix2 & IND2_MICRO)
		rawval *= 1E-6;
	else if (rs_packet->indicatrix1 & IND1_MILI)
		rawval *= 1E-3;
	else if (rs_packet->indicatrix1 & IND1_KILO)
		rawval *= 1E3;
	else if (rs_packet->indicatrix1 & IND1_MEGA)
		rawval *= 1E6;

	return rawval;
}

static gboolean is_celsius(const struct rs9lcd_packet *rs_packet)
{
	return ((rs_packet->digit4 & ~DP_MASK) == LCD_C);
}

static gboolean is_shortcirc(const struct rs9lcd_packet *rs_packet)
{
	return ((rs_packet->digit2 & ~DP_MASK) == LCD_h);
}

static gboolean is_logic_high(const struct rs9lcd_packet *rs_packet)
{
	sr_spew("Digit 2: 0x%02x.", rs_packet->digit2 & ~DP_MASK);
	return ((rs_packet->digit2 & ~DP_MASK) == LCD_H);
}

SR_PRIV int sr_rs9lcd_parse(const uint8_t *buf, float *floatval,
			    struct sr_datafeed_analog *analog, void *info)
{
	const struct rs9lcd_packet *rs_packet = (void *)buf;
	double rawval;

	(void)info;

	rawval = lcd_to_double(rs_packet, READ_ALL);

	switch (rs_packet->mode) {
	case MODE_DC_V:
		analog->mq = SR_MQ_VOLTAGE;
		analog->unit = SR_UNIT_VOLT;
		analog->mqflags |= SR_MQFLAG_DC;
		break;
	case MODE_AC_V:
		analog->mq = SR_MQ_VOLTAGE;
		analog->unit = SR_UNIT_VOLT;
		analog->mqflags |= SR_MQFLAG_AC;
		break;
	case MODE_DC_UA:	/* Fall through */
	case MODE_DC_MA:	/* Fall through */
	case MODE_DC_A:
		analog->mq = SR_MQ_CURRENT;
		analog->unit = SR_UNIT_AMPERE;
		analog->mqflags |= SR_MQFLAG_DC;
		break;
	case MODE_AC_UA:	/* Fall through */
	case MODE_AC_MA:	/* Fall through */
	case MODE_AC_A:
		analog->mq = SR_MQ_CURRENT;
		analog->unit = SR_UNIT_AMPERE;
		analog->mqflags |= SR_MQFLAG_AC;
		break;
	case MODE_OHM:
		analog->mq = SR_MQ_RESISTANCE;
		analog->unit = SR_UNIT_OHM;
		break;
	case MODE_FARAD:
		analog->mq = SR_MQ_CAPACITANCE;
		analog->unit = SR_UNIT_FARAD;
		break;
	case MODE_CONT:
		analog->mq = SR_MQ_CONTINUITY;
		analog->unit = SR_UNIT_BOOLEAN;
		rawval = is_shortcirc(rs_packet);
		break;
	case MODE_DIODE:
		analog->mq = SR_MQ_VOLTAGE;
		analog->unit = SR_UNIT_VOLT;
		analog->mqflags |= SR_MQFLAG_DIODE | SR_MQFLAG_DC;
		break;
	case MODE_HZ:		/* Fall through */
	case MODE_VOLT_HZ:	/* Fall through */
	case MODE_AMP_HZ:
		analog->mq = SR_MQ_FREQUENCY;
		analog->unit = SR_UNIT_HERTZ;
		break;
	case MODE_LOGIC:
		/*
		 * No matter whether or not we have an actual voltage reading,
		 * we are measuring voltage, so we set our MQ as VOLTAGE.
		 */
		analog->mq = SR_MQ_VOLTAGE;
		if (!isnan(rawval)) {
			/* We have an actual voltage. */
			analog->unit = SR_UNIT_VOLT;
		} else {
			/* We have either HI or LOW. */
			analog->unit = SR_UNIT_BOOLEAN;
			rawval = is_logic_high(rs_packet);
		}
		break;
	case MODE_HFE:
		analog->mq = SR_MQ_GAIN;
		analog->unit = SR_UNIT_UNITLESS;
		break;
	case MODE_DUTY:		/* Fall through */
	case MODE_VOLT_DUTY:	/* Fall through */
	case MODE_AMP_DUTY:
		analog->mq = SR_MQ_DUTY_CYCLE;
		analog->unit = SR_UNIT_PERCENTAGE;
		break;
	case MODE_WIDTH:	/* Fall through */
	case MODE_VOLT_WIDTH:	/* Fall through */
	case MODE_AMP_WIDTH:
		analog->mq = SR_MQ_PULSE_WIDTH;
		analog->unit = SR_UNIT_SECOND;
		break;
	case MODE_TEMP:
		analog->mq = SR_MQ_TEMPERATURE;
		/* We need to reparse. */
		rawval = lcd_to_double(rs_packet, READ_TEMP);
		analog->unit = is_celsius(rs_packet) ?
				SR_UNIT_CELSIUS : SR_UNIT_FAHRENHEIT;
		break;
	case MODE_DBM:
		analog->mq = SR_MQ_POWER;
		analog->unit = SR_UNIT_DECIBEL_MW;
		analog->mqflags |= SR_MQFLAG_AC;
		break;
	default:
		sr_dbg("Unknown mode: %d.", rs_packet->mode);
		break;
	}

	if (rs_packet->info & INFO_HOLD)
		analog->mqflags |= SR_MQFLAG_HOLD;
	if (rs_packet->digit4 & DIG4_MAX)
		analog->mqflags |= SR_MQFLAG_MAX;
	if (rs_packet->indicatrix2 & IND2_MIN)
		analog->mqflags |= SR_MQFLAG_MIN;
	if (rs_packet->info & INFO_AUTO)
		analog->mqflags |= SR_MQFLAG_AUTORANGE;

	*floatval = rawval;
	return SR_OK;
}