SC2262 / SC2272 Testing

SC2262 / SC2272 Emulation in Software Testing

A study for datalogging Harbor Freight PIR sensors

Once upon a time I had a need to decode a RF remote control for a project. The remote control used an encoding chip SC2262. A second source for the part is PT2262. The typical receiver for these signals use variations of a decoder chip SC2272 or PT2272.

A recent project needed to log activations from multiple PIR sensors. The particular PIR sensors are sold by Harbor Freight. The sensor uses the SC2262 encoder. Each PIR comes with a matching receiver that puts out an annoying double beep for every trigger of the PIR sensor. The receiver uses a decoder chip with proprietary markings. It may or may not be SC/PT2272 variant. It doesn't matter since Harbor Freight channel numbers are based on the address mode instead of using the data nibble. The typical SC/PT2272 chips don't provide the address as an output. They look for a specific address and signals you when that address is detected. This arrangement is not suitable for tracking multiple sensors.

What was needed is a receiver that can receive and decode broadcasts from multiple PIR sensors.

This Arduino code receives the raw data stream, isolates all 12 bits of address and data of the SC2262 protocol, making it available to the program for further processing. It took a little effort to figure it out, but not that hard given the spec sheet.

Part of the project needed some kind of relaying device to extend the range and/or change the data for some sensor locations. So the SC2262 encoding code was also ported to Arduino code.

The code presented here is definitely a hack. It does not show the whole project. Just the bits for testing the encoding and decoding of the protocol. It does not use any library features, but is easy to follow as to what is going on, I hope. It does work, but could use some clean up.

PT2272_SIM.ino PT2272_SIM.ino

// PT2272_SIM.ino
// SC2272/PT2272 Emulation Test
// By Thomas Olson
// Rev. teo20130130.02
// For Arduino

/*
Grab and measure widths of the next 120 pos/neg pulses.
Get timestamps and polarity of all pulse edges for SAMPLES.
Analyze the timestamps to obtain the four types of pulses...
shortlow, longlow, shorthigh, longhigh.
Analyze the combinations to determine 22x2 tristate values...
1, 0, or F, or S(ync)
First attempt assumes 4.7Mohm/820Kohm set
*/

/* TODO:
 - Determine osc times for other two popular resistor settings.
  1.2M/220K and 1.5M/270K
 - What other things are running at 433MHz with different protocols
  
*/

#define FoscCshort 500 // nominal short pulse uS 
#define FoscClong 1500 // nominal long pulse uS
#define FoscTol 200      // tolerance uS

#define SHORTMAX FoscCshort + FoscTol
#define SHORTMIN FoscCshort - FoscTol
#define LONGMAX  FoscClong + FoscTol
#define LONGMIN  FoscClong - FoscTol

// Pin 13 has an LED connected on most Arduino boards.
// give it a name:
int led = 13;
long starttime, stoptime;
int rfdata_in = 3; //PD3 (INT1)

#define SAMPLES 120
unsigned long edges[SAMPLES]; // store time in microseconds
unsigned long pulses[SAMPLES]; // store pulses in microseconds <65535uS
unsigned char polarity[SAMPLES];
char pulsePair[SAMPLES];
char addressData[SAMPLES];

void setup() {                

  pinMode(led, OUTPUT);     
  Serial.begin(115200);
  pinMode(rfdata_in,INPUT);
  while(!Serial){;}

}

void loop() {
  
  for(int x;x<SAMPLES;x++) pulsePair[x]='0';
  for(int x;x<SAMPLES;x++) addressData[x]='\0';

  for(int x=0; x<SAMPLES; x+=2){
 
    while(!(PIND & (1<<rfdata_in)));  //Serial.println("LOW->HIGH");
    // low to high edge detected
    edges[x] = micros();
    polarity[x] = 1;
//    Serial.println("0>1 ");
    while((PIND & (1<<rfdata_in)));  //Serial.println("HIGH->LOW");
    // high to low edge detected
    edges[x+1] = micros();
    polarity[x+1] = 0;
//   Serial.println("1>0 ");
  }

  digitalWrite(led, HIGH); // LED ON after edges samples detected
 
  for(int x=1; x<SAMPLES; x++){
    pulses[x-1] = edges[x] - edges[x-1]; // pulse widths
  }
  
  //NOTE: array position 0 should be a high polarity pulse
  //So assuming so, then all odd values are low.
  for(int x=0; x<SAMPLES; x+=2){ 
      //Assuming nominal short pulse are 500uS and long are 1500uS
      if(pulses[x] > pulses[x+1]){ // Hi longer Lo might be ONE
        if(pulses[x]>LONGMIN && pulses[x]<LONGMAX) //LongHigh valid
          if(pulses[x+1]>SHORTMIN && pulses[x+1]<SHORTMAX) //ShortLow valid
            //valid interim digit 1
            pulsePair[x/2]='1';
            
      }else if(pulses[x] < pulses[x+1]){ // Hi shorter than Lo- ZERO? or SYNC?
        if(pulses[x]>SHORTMIN && pulses[x]<SHORTMAX) //ShortHigh valid
          if(pulses[x+1]>LONGMIN && pulses[x+1]<LONGMAX){ //LongLo valid
            //valid interim digit 0
             pulsePair[x/2]='0';
          }else if(pulses[x+1]>14400 && pulses[x+1]<<17600){  //Sync valid
            // valid interim digit S(ync)
            pulsePair[x/2]='S';
          }
      }
  }

  // Analyse to get actual security CODES
  int x=0;
  int y=0;

// Find the first S
  while(pulsePair[x] != 'S' && x<SAMPLES/2) x++;


//Found S so start converting until next S
  x++;
  
  while(pulsePair[x] != 'S' && x<SAMPLES/2){  
  if(pulsePair[x]=='0' && pulsePair[x+1]=='0'){
//    Serial.print('0'); //ZERO LO (00)
    addressData[y]='0';
  }else if(pulsePair[x]=='1' && pulsePair[x+1]=='1'){
//    Serial.print('1'); // ONE HI (11)
    addressData[y]='1';
  }else if(pulsePair[x]=='0' && pulsePair[x+1]=='1'){
//    Serial.print('F'); // Float TriState (01)
    addressData[y]='F';
  }else{
//    Serial.print('U'); // Undefined (10)
    addressData[y]='U';
  }
  x+=2;
  y++;
  }
  
  if(pulsePair[x] == 'S'){
    
    addressData[y]='\0'; // NULL ends string

    Serial.print(addressData); //Print if not empty
    if(!strcmp(addressData,"00F0FF00FFFF")){
    //  Serial.print(addressData);
      Serial.println(" CH 15 - Family Room Alert");
    }else
    if(!strcmp(addressData,"F000FF00FFFF")){
    //  Serial.print(addressData);
      Serial.println(" CH 13 - Garage Alert");
    }else
      Serial.println(" - Unknown Device");
    
    clearAddressData;
    delay(1500);  
  } // test for S
  
  
  digitalWrite(led, LOW); // LED off after edge samples detected
  

//  delay(400);
}

void clearAddressData(void){
  for(int x;x<SAMPLES/2;x++) addressData[x] = '\0';
}

PT2262_SIM.ino PT2262_SIM.ino

// PT2262_SIM.ino
// SC2262/PT2262 Emulation Test
// By Thomas Olson
// Rev. teo20130130.02
// For Arduino


int xmtrPin = 8; // To transmitter device.

// The data rate is determined by Resistor on [SC|PT]2262
// Typical 4.7Mohm, 1.5Mohm, 1.2Mohm
#define ROHM R4M7

#if ROHM == R4M7
  #define PULSESHORT 500  // confirmed
  #define PULSELONG  1500
  #define PULSESYNC  16000 // Aproximately 10.67 times PULSELONG
#elif ROHM == R1M5
  #define PULSESHORT 160  // assumed
  #define PULSELONG 500
  #define PULSESYNC 5333
#elif ROHM == R1M2
  #define PULSESHORT 128  // Not sure about these values
  #define PULSELONG 400
  #define PULSESYNC 4267
#endif

void setup() {
    pinMode(xmtrPin, OUTPUT);
    digitalWrite(xmtrPin,LOW); // Make sure tx pin is LOW
    Serial.begin(115200);
    delay(1000);
}

static void ookPulse(int on, int off) {
  digitalWrite(xmtrPin, HIGH);
  delayMicroseconds(on);
  digitalWrite(xmtrPin, LOW);
  delayMicroseconds(off);
}

// pt2262 requires 12 bits or '0','1','F' followed by a 'S(ync)'
// need to send the 12 bit and sync packet at least 4 times in a row.
// NOTE: When the last four bits are meant to be data the recognized
// bits for official [SC|PT2272] chips are '0' or '1'. I.E. the 'F' state
// is for addresses only.
// In my private network, I allow 'F' as well as 'U'.

// This version doesn't have any validation on the 12 bits of the packet.
// Or verifies that there are 12 bits to transmit. So make sure the
// transmit string has 12 members.
static void pt2262Send(char packet[12]) {
//  Serial.println(packet);
  for(int repeat=0; repeat<4; repeat++){

    for(int x=0;x<12;x++){
    
      switch (packet[x]) {
    
        case '0':  // 00
          ookPulse(PULSESHORT,PULSELONG);
          ookPulse(PULSESHORT,PULSELONG);
          break;
      
        case '1':  // 11
          ookPulse(PULSELONG,PULSESHORT);
          ookPulse(PULSELONG,PULSESHORT);
          break;
    
        case 'F':  // 01
        case 'f':
          ookPulse(PULSESHORT,PULSELONG);
          ookPulse(PULSELONG,PULSESHORT);
          break;
    
        case 'U':  // 10 (Technicaly undefined, but ;)
        case 'u':
        default:
          ookPulse(PULSELONG,PULSESHORT);
          ookPulse(PULSESHORT,PULSELONG);
          break;
      } // switch
    } // for loop
    ookPulse(PULSESHORT,PULSESYNC); // S(ync)
  } // repeat
}


void loop() {

    pt2262Send("00F0FF00FFFF");  // CH 15

    delay(3000);
    
    pt2262Send("F000FF00FFFF");  // CH 13
  
    delay(3000);

}

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