WiFi_433_Transceiver/main/Sensors/esic.c

#include "esic.h"
#include <stdint.h>
#include <stdio.h>
#include "esp_log.h"
#include "../rxTimer.h"
#include "../led.h"

/**
**********************************************************************************
* TEMP 3
* ESIC WT450H

    +---+   +---+   +-------+       +  high
    |   |   |   |   |       |       |
    |   |   |   |   |       |       |
    +   +---+   +---+       +-------+  low
    
    ^       ^       ^       ^       ^  clock cycle
    |   1   |   1   |   0   |   0   |  translates as
    
    Each transmission is 36 bits long (i.e. 72 ms)

	.short_width = 976,  // half-bit width 976 us
    .long_width  = 1952, // bit width 1952 us
    
    Data is transmitted in pure binary values, NOT BCD-coded.
    
    Example transmission (House 1, Channel 1, RH 59 %, Temperature 23.5 �C)
    1100 00010011001110110100100110011000
    
    b00 - b03  (4 bits): Constant, 1100, probably preamble
    b04 - b07  (4 bits): House code (here: 0001 = HC 1)
    b08 - b09  (2 bits): Channel code - 1 (here 00 = CC 1)
    b10 - b12  (3 bits): Constant, 110
    b13 - b19  (7 bits): Relative humidity (here 0111011 = 59 %)
    b20 - b34 (15 bits): Temperature (see below)
    b35 - b35  (1 bit) : Parity (xor of all bits should give 0)
    
    The temperature is transmitted as (temp + 50.0) * 128,
    which equals (temp * 128) + 6400. Adding 50.0 �C makes
    all values positive, an unsigned 15 bit integer where the
    first 8 bits correspond to the whole part of the temperature
    (here 01001001, decimal 73, substract 50 = 23).
    Remaining 7 bits correspond to the fractional part.
    
    To avoid floating point calculations I store the raw temperature value
    as a signed integer in the variable esicTemp, then transform it to
    actual temperature * 10 using "esicTemp = (esicTemp - 6400) * 10 / 128",
    where 6400 is the added 50 times 128.
    When reporting the temperature I simply print "esicTemp / 10" (integer division,
    no fraction), followed by a decimal point and "esicTemp % 10" (remainder, which
    equals first fractional decimal digit).
      
    Summary of bit fields:
    1100 0001 00 110 0111011 010010011001100 0
     c1   hc  cc  c2    rh          t        p
     
    c1, c2 = constant field 1 and 2
    hc, cc = house code and channel code
    rh, t  = relative humidity, temperature
    p      = parity bit 1111111111111110


	This interpretation is from: https://github.com/merbanan/rtl_433/blob/master/src/devices/wt450.c

	   1100 0001 | 0011 0011 | 1000 0011 | 1011 0011 | 0001
	   xxxx ssss | ccxx bhhh | hhhh tttt | tttt tttt | sseo

	- x: constant
	- s: House code
	- c: Channel
	- b: battery low indicator (0=>OK, 1=>LOW)
	- h: Humidity
	- t: Temperature, 12 bit, offset 50, scale 16
	- s: sequence number of message repeat
	- e: parity of all even bits
	- o: parity of all odd bits

**********************************************************************************
*/



volatile unsigned long long temp3_x_data;


void ESIC_ResetDecoder() {
	temp3_x_data = 0;
}

#define NO_OF_PULSES 60
#define max(a,b) (((a)>(b))?(a):(b))
#define isShortPulse(width)  (((long_pulse/2)-maxDiff) <= width && width <= ((long_pulse/2)+maxDiff))
#define isLongPulse(width)  ((long_pulse-maxDiff) <= width && width <= (long_pulse+maxDiff))

unsigned int temp3_pulses[NO_OF_PULSES];


static int long_pulse = 1955;
static int maxDiff = 300;

static void storePulses(unsigned int inWidth) {

	int i;

	// Shift pulses down
	for(i=1;i<NO_OF_PULSES;i++) {
		temp3_pulses[i-1] = temp3_pulses[i];
	}

	temp3_pulses[NO_OF_PULSES-1] = inWidth;
}

static void sweepForNoise() {

	// If we have a short pulse in position 2
	// Then add together pos 1,2 and 3 if they are a valid pulse
	// This way we can handle one single noise pulse in a real pulse
	if( temp3_pulses[NO_OF_PULSES-2] < ((long_pulse/2)-maxDiff) ) {

		int totPulse = temp3_pulses[NO_OF_PULSES-1]+temp3_pulses[NO_OF_PULSES-2]+temp3_pulses[NO_OF_PULSES-3];
		
		if( isShortPulse(totPulse) || isLongPulse(totPulse) ) {
			
			// Store new pulse in last position
			temp3_pulses[NO_OF_PULSES-1] = totPulse;

			// Move everything up again
			for(int i=NO_OF_PULSES-2;i>1;i--) {
				temp3_pulses[i] = temp3_pulses[i-2];
			}
			temp3_pulses[0] = 0;
			temp3_pulses[1] = 0;
		}
	}
}


/*static void adjustTiming() {

	int p1 = temp3_pulses[NO_OF_PULSES-8];
	int p2 = temp3_pulses[NO_OF_PULSES-7];
	int p3 = temp3_pulses[NO_OF_PULSES-6];
	int p4 = temp3_pulses[NO_OF_PULSES-5];
	int p5 = temp3_pulses[NO_OF_PULSES-4];
	int p6 = temp3_pulses[NO_OF_PULSES-3];
	int p7 = temp3_pulses[NO_OF_PULSES-2];
	int p8 = temp3_pulses[NO_OF_PULSES-1];

	// Check max differance between the short pulses
	int sh_mean = (p1+p2+p3+p4) / 4;
	int sh_max_diff = max(max(abs(p1-sh_mean),abs(p2-sh_mean)),max(abs(p3-sh_mean),abs(p4-sh_mean)));

	// Check max differance between the long pulses
	int long_mean = (p5+p6+p7+p8) / 4;
	int long_max_diff = max(max(abs(p5-long_mean),abs(p6-long_mean)),max(abs(p7-long_mean),abs(p8-long_mean)));

	if( sh_max_diff < maxDiff && long_max_diff < maxDiff ) {

		int mean = (long_mean + sh_mean)/2;
		if( long_mean > (mean+maxDiff) && sh_mean < (mean-maxDiff) ) {
			if( abs(long_mean - (sh_mean*2)) < maxDiff ) {
				long_pulse = (long_mean + sh_mean*2)/2;
				maxDiff = long_mean / 15;
			}
		}
	}
}*/

// The latest/newest pulse is at the end of the array [59]
// This ([59]) is the latest bit in the bit-stream from the transmitter
// This is way we input the bits at a high position and shift them towards lower values
// So..start reading backwards and working towards the first/highest bits
static int checkPulsePattern() {

	int i = NO_OF_PULSES-1;	// Start reading from the last received (end of array)
	int b = 0;

	unsigned long long code = 0;

	while( i >= 0 ) {

		int combWidth = temp3_pulses[i] + temp3_pulses[i-1];

		if( isLongPulse(temp3_pulses[i]) ) {
			b++;
			i-=1;
			code = code >> 1;
		}
		else if( isShortPulse(temp3_pulses[i]) && isShortPulse(temp3_pulses[i-1]) ) {
			b++;
			i-=2;
			code = ((code >> 1) | 0x200000000);
		}
		else if( isLongPulse( combWidth ) ) {
			b++;
			i-=2;
			code = ((code >> 1) | 0x200000000);
		}
		else {
			return -1;
		}
		if( b == 34 ) {
/*
		0000 0001 00 110 0101000 010010110101000 1
AND:    0011 1111 00 111 0000000 000000000000000 0  = 001111110011100000000000000000000000 = 0x3F3800000
RES:    0000 0001 00 110 0000000 000000000000000 0  = 000000010011000000000000000000000000 = 0x013000000

		Summary of bit fields:
		1100 0001 00 110 0111011 010010011001100 0
		 c1   hc  cc  c2    rh          t        p
		 */
			if( (code & 0x3F3800000) == 0x013000000 ) {

				temp3_x_data = (code&0xFFFFFFFF);
				// Check parity
				int even=0;
				unsigned long long data = temp3_x_data;
				for(int i=0;i<32;i++) {
					if( data & 1 ) even++;
					data >>= 1;
				}
				if( even % 2 != 0 ) {
					return -1;
				}
				// A correct code has been received
				//printf("Code received: %llu on row:%d\n",(code&0xFFFFFFFF),row_no);
				temp3_x_data &= 0xFFFFFFF0;	// Remove sequence and parity bits in lowest nibble
				return 1;
				
			}
			else {
				return -1;
			}
		}
	}
	return 0;
}

static int temp3decode (unsigned int inWidth) {

	int width = inWidth; //preProcessPulses(inWidth);

	if( width == -1 ) return -1;
	if( width == 0 ) return 0;

	storePulses(inWidth);
	sweepForNoise();
	//adjustTiming();
	return checkPulsePattern();
}

int64_t nextPulseESICSensor(uint32_t width) {
  
  	static int64_t previous_data = 0;
	static uint32_t old_time=0;
	static uint32_t now;
	int64_t retVal = -1;
  
	if( width > 0 ) {
		if( temp3_x_data == 0 ) {
			temp3decode(width);
		}
	}
  
	if( temp3_x_data > 0 ) {
		now = millis();

		if( temp3_x_data != previous_data || (now > (old_time+1000)) ) {
            previous_data = temp3_x_data;
            retVal = temp3_x_data;
            blinkTheLED();
		}
		old_time = now;
		ESIC_ResetDecoder();
	}
	
	return retVal;
}