That's true but i need to shift bit by bit until i find a match so skipping a clock might not be best method as the data might be the particular preamble first bit(the preamble can be anywhere i don't where it starts so shift bit by bit 1st until match found).

No it is working fine and there no necessity for me make it 8 bit but for just better understanding that if the state machine works for 4 bit then if we do slight modification on the state machine it should work for 8 bit. So i modified the state machine as well as getNibble() function but it does not read any data so i came to forum for possible solution(I am work alone so i have no other alternative).

Just for curiosity i tried to read byte by byte rather than nibble by nibble but it does not read the data at all. Can anybody indicate where i am doing wrong.

Code:

const int CLOCK_PIN     =     2;
const int DATA_PIN      =     4;
const int PACKET_BITS   =     1024;
const int PREAMBLE_LEN  =     3;
const int DATA_LEN      =     ((PACKET_BITS / 8) - PREAMBLE_LEN);

enum {
    PRE_0,    PRE_1,    PRE_2,    PRE_3,    PRE_4,    PRE_5,    DATA
} states;   

byte     preamble [] = {0xCA,0xAC,0x1F};
char     hexAsciiVals[] = "0123456789ABCDEF0123456789ABCDEF";
byte     state = PRE_0;
byte     nibble;
int      nibble_count = 0;
byte     firstval;
//const char  header = "CAAC1F";

void setup() {
  pinMode(CLOCK_PIN, INPUT);
  pinMode(DATA_PIN, INPUT);
  Serial.begin(57600);
}

void loop() {

    nibble = getNibble();
    //nibble_count++;
   
   
    switch (state) {   
        case PRE_0:
//            if (nibble_count > PREAMBLE_LEN + DATA_LEN) {
//                // we've read 32 bytes and still not found a match
//                // for the preamble so skip a clock pulse
//                while (digitalRead(CLOCK_PIN) == LOW);
//                while (digitalRead(CLOCK_PIN) == HIGH);
//                nibble_count = 0;
//            } else
//            {
//                firstval = 12;
//                Serial.write(hexAsciiVals[firstval]);
               
                state = (nibble == preamble[0]) ? PRE_1 : PRE_0;
              //  Serial.write(hexAsciiVals[nibble]);
//            }
            break;
       
        case PRE_1:
           
           // Serial.write (hexAsciiVals[firstval]);
           // Serial.print(hexAsciiVals[12]);
           // Serial.print(hexAsciiVals[nibble]);
            state = (nibble == preamble[1]) ? PRE_2 : PRE_0;   
            //Serial.write (hexAsciiVals[nibble]);
            break;
           
        case PRE_2:
          //  Serial.print(hexAsciiVals[nibble]);
            state = (nibble == preamble[2]) ? DATA : PRE_0;
            //Serial.write (hexAsciiVals[nibble]);
            break;

//        case PRE_3:
//          //  Serial.print(hexAsciiVals[nibble]);
//            state = (nibble == preamble[3]) ? PRE_4 : PRE_0;
//        //    Serial.write (hexAsciiVals[nibble]);
//            break;
//
//        case PRE_4:
//           // Serial.print(hexAsciiVals[nibble]);
//            state = (nibble == preamble[4]) ? PRE_5 : PRE_0;
//           // Serial.write (hexAsciiVals[nibble]);
//            break;
//       
//        case PRE_5:
//           // Serial.print(hexAsciiVals[nibble]);
//    //        Serial.print(202, HEX);
//  //          Serial.print(172, HEX);
//        //    Serial.println();
//            state = (nibble == preamble[5]) ? DATA : PRE_0;
//            Serial.print("$");
//            //   nibble_count = 0;
//            break;
           
        case DATA:
           //   Serial.print("CAAC1F");
            Serial.print(nibble, HEX);
            if (nibble_count == DATA_LEN) {
                // all done, start again
                state = PRE_0;
                nibble_count = 0;
             //   Serial.print("\n");
           //     Serial.print(hexAsciiVals[12]);
               
            }
           
            nibble_count++;
            //Serial.println();
            break;
    }
   
  //  delay(10);
}

byte getNibble() {

    byte val = 0;
   
    for (byte bit_count = 0; bit_count < 8; bit_count++) {
        while (digitalRead(CLOCK_PIN) == HIGH);
        while (digitalRead(CLOCK_PIN) == LOW);
        val <<= 1;
        val |= digitalRead(DATA_PIN);
    }
    return (val &= 0xFF);
}

Ok Mr. PaulS I will make the packet in a way you have describe(because i am also the sender).

Hey sorry for the last one. Here the compile code.

Code:

char serial_data[100];
int index = 0;
char data;
void setup()
{
  Serial.begin(9600);
 
}

void loop()
{
  if(Serial.available()>0)
  {
   data = Serial.read();
//    if(ch[0] == "A" )
//    {
   serial_data[index++] = data;
          
//      char frstchar = buff[0];
     if(serial_data[0] == 'A')
//    for(int i = 0; i<=20; i++)
    {

     Serial.print(1, DEC);
//     delay(500);
    }
   else
          Serial.print(0, DEC);
  }
  delay(500);
}

I followed the procedure what Mr. PaulS suggested yet still not able to detect the character "A".

Code:

char serial_data[100];
int index = 0;

void setup()
{
  Serial.begin(9600);
 
}

void loop()
{
  if(Serial.available()>0)
  {
    for(int index = 0; index <=20; index++)
     char data = Serial.read();

//    if(ch[0] == "A" )
//    {
 
      serial_data[index] = data;
     
  }
           
//      char frstchar = buff[0];
     if(serial_data[0] == 'A')
//    for(int i = 0; i<=20; i++)
    {

     Serial.print(1, DEC);
//     delay(500);
    }
   else
          Serial.print(0, DEC);
  }
  delay(500);
} 

The generally accepted ratio of answers to questions is 1.0 or higher. Your ratio is a lot lower than that.

Sorry I did not get you.

Thanks & Reagrds

Niladri

Yeah that i have it in my mind but the data i read from serial read is one byte i cannot store in a array or if i store it a char then the entire data is one character that i don't no any traversal technique of find a character in a one "big character"???

Thanks & Regards

Niladri

Not exactly. I found the substring example sketch so i tried to use that but if i don't use typecasting it says " Invalid conversion from int to const char*". My main requirement is i will have set of data preceding with A B C etc so that it will be my indicator that i have to read next 4 character do engineering conversion to make floating data if you better solution/idea please post it.

Thanks & Regards

Niladri   

Sorry...

Code:

void setup()
{
  Serial.begin(9600);
 
}

void loop()
{
  if(Serial.available()>0)
  {
 
     String data = (String)Serial.read();
//     char* serial_data[20]={data};
//   char *ch= serial_data;
   
//    if(ch[0] == "A" )
//    {
     if(data.substring(0,4) == "A1234")
//    for(int i = 0; i<=20; i++)
    {

     Serial.print(1);
//     delay(500);
    }
   else
          Serial.print(0);
  }
  delay(500);
}

Hi guys i am reading some string("A1234B1234C1234" test data)at arduino via Serial.read() now i want to identify the Character "B" and read next 4 data. I tried using substring but it is not getting detected. Any idea??

Thanks & Regards

Niladri

OK i will try that but what the port response?
Still i need to program it every time to make it transmit just powering it up does not make it transmit(Tx LED is not glowing)

Hi guys I should not start this new thread but problem is different
In my previous post i asked about reading data at 10 khz and with everybody help(especially Mr. Graynomad hats off to you!) we are able to solve it
But in the code we are using state machine to check the header("CAAC1F") but if i put any serial print inside those state it does not respond it keep on stuck on first state and also when we put some special character the behavior of the port changes(some time the port transmits and some times it does not arbitrarily )  

Code:

const int CLOCK_PIN     =     2;
const int DATA_PIN      =     4;
const int PACKET_BITS   =     1024;
const int PREAMBLE_LEN  =     6;
const int DATA_LEN      =     ((PACKET_BITS / 4) - PREAMBLE_LEN);

enum {
    PRE_0,    PRE_1,    PRE_2,    PRE_3,    PRE_4,    PRE_5,    DATA
} states;    

byte     preamble [] = {0x0C,0x0A,0x0A,0x0C,0x01,0x0F};
char     hexAsciiVals[] = "0123456789ABCDEF";
byte     state = PRE_0;
byte     nibble;
int      nibble_count = 0;
byte     firstval;
//const char  header = "CAAC1F";

void setup() {
  pinMode(CLOCK_PIN, INPUT);
  pinMode(DATA_PIN, INPUT);
  Serial.begin(57600);
}

void loop() {

    nibble = getNibble();
    //nibble_count++;
    
    
    switch (state) {    
        case PRE_0:
//            if (nibble_count > PREAMBLE_LEN + DATA_LEN) {
//                // we've read 32 bytes and still not found a match
//                // for the preamble so skip a clock pulse
//                while (digitalRead(CLOCK_PIN) == LOW);
//                while (digitalRead(CLOCK_PIN) == HIGH);
//                nibble_count = 0;
//            } else
//            {
//                firstval = 12;
//                Serial.write(hexAsciiVals[firstval]);
                
                state = (nibble == preamble[0]) ? PRE_1 : PRE_0;
              //  Serial.write(hexAsciiVals[nibble]);
//            }
            break;
        
        case PRE_1:
            
           // Serial.write (hexAsciiVals[firstval]);
           // Serial.print(hexAsciiVals[12]);
           // Serial.print(hexAsciiVals[nibble]);
            state = (nibble == preamble[1]) ? PRE_2 : PRE_0;    
            //Serial.write (hexAsciiVals[nibble]);
            break;
            
        case PRE_2:
          //  Serial.print(hexAsciiVals[nibble]);
            state = (nibble == preamble[2]) ? PRE_3 : PRE_0;
            //Serial.write (hexAsciiVals[nibble]);
            break;

        case PRE_3:
          //  Serial.print(hexAsciiVals[nibble]);
            state = (nibble == preamble[3]) ? PRE_4 : PRE_0;
        //    Serial.write (hexAsciiVals[nibble]);
            break;

        case PRE_4:
           // Serial.print(hexAsciiVals[nibble]);
            state = (nibble == preamble[4]) ? PRE_5 : PRE_0;
           // Serial.write (hexAsciiVals[nibble]);
            break;
        
        case PRE_5:
           // Serial.print(hexAsciiVals[nibble]);
    //        Serial.print(202, HEX);
  //          Serial.print(172, HEX);
        //    Serial.println();
            state = (nibble == preamble[5]) ? DATA : PRE_0;
            Serial.print("$");
            //   nibble_count = 0;
            break;
            
        case DATA:
           //   Serial.print("CAAC1F");
            Serial.write(hexAsciiVals[nibble]);
            if (nibble_count == DATA_LEN) {
                // all done, start again
                state = PRE_0;
                nibble_count = 0;
             //   Serial.print("\n");
           //     Serial.print(hexAsciiVals[12]);
                
            }
            
            nibble_count++;
            //Serial.println();
            break;
    }
    
  //  delay(10);
}

byte getNibble() {

    byte val = 0;
    
    for (byte bit_count = 0; bit_count < 4; bit_count++) {
        while (digitalRead(CLOCK_PIN) == HIGH);
        while (digitalRead(CLOCK_PIN) == LOW);
        val <<= 1;
        val |= digitalRead(DATA_PIN);
    }
    return (val &= 0x0F);
}

Any idea???

Finally it's working thanks everyone for their help and support without your help it would not been possible and i am posting the working code if in case anyone wants to refer it for their future use....
Thanks...

Code:

const int CLOCK_PIN     =     2;
const int DATA_PIN      =     4;
const int PACKET_BITS   =     256;
const int PREAMBLE_LEN  =     6;
const int DATA_LEN      =     ((PACKET_BITS / 4) - PREAMBLE_LEN);

enum {
    PRE_0,    PRE_1,    PRE_2,    PRE_3,    PRE_4,    PRE_5,    DATA
} states;   

byte     preamble [] = {0x0C,0x0A,0x0A,0x0C,0x01,0x0F};
char     hexAsciiVals[] = "0123456789ABCDEF";
byte     state = PRE_0;
byte     nibble;
int      nibble_count = 0;
byte     firstval;

void setup() {
  pinMode(CLOCK_PIN, INPUT);
  pinMode(DATA_PIN, INPUT);
  Serial.begin(9600);
}

void loop() {

    nibble = getNibble();
    //nibble_count++;
   
   
    switch (state) {   
        case PRE_0:
//            if (nibble_count > PREAMBLE_LEN + DATA_LEN) {
//                // we've read 32 bytes and still not found a match
//                // for the preamble so skip a clock pulse
//                while (digitalRead(CLOCK_PIN) == LOW);
//                while (digitalRead(CLOCK_PIN) == HIGH);
//                nibble_count = 0;
//            } else
//            {
//                firstval = 12;
//                Serial.write(hexAsciiVals[firstval]);
               
                state = (nibble == preamble[0]) ? PRE_1 : PRE_0;
              //  Serial.write(hexAsciiVals[nibble]);
//            }
            break;
       
        case PRE_1:
           
           // Serial.write (hexAsciiVals[firstval]);
           // Serial.print(hexAsciiVals[12]);
            Serial.print(hexAsciiVals[nibble]);
            state = (nibble == preamble[1]) ? PRE_2 : PRE_0;   
            //Serial.write (hexAsciiVals[nibble]);
            break;
           
        case PRE_2:
            Serial.print(hexAsciiVals[nibble]);
            state = (nibble == preamble[2]) ? PRE_3 : PRE_0;
            //Serial.write (hexAsciiVals[nibble]);
            break;

        case PRE_3:
            Serial.print(hexAsciiVals[nibble]);
            state = (nibble == preamble[3]) ? PRE_4 : PRE_0;
            //Serial.write (hexAsciiVals[nibble]);
            break;

        case PRE_4:
            Serial.print(hexAsciiVals[nibble]);
            state = (nibble == preamble[4]) ? PRE_5 : PRE_0;
            //Serial.write (hexAsciiVals[nibble]);
            break;
       
        case PRE_5:
            Serial.print(hexAsciiVals[nibble]);
            state = (nibble == preamble[5]) ? DATA : PRE_0;
            //Serial.write (hexAsciiVals[nibble]);
            //   nibble_count = 0;
            break;
           
        case DATA:
           
            Serial.print(hexAsciiVals[nibble]);
            if (nibble_count == DATA_LEN) {
                // all done, start again
                state = PRE_0;
                nibble_count = 0;
                Serial.println(' ');
                Serial.print(hexAsciiVals[12]);
               
            }
           
            nibble_count++;
            //Serial.println();
            break;
    }
   
  //  delay(10);
}

byte getNibble() {

    byte val = 0;
   
    for (byte bit_count = 0; bit_count < 4; bit_count++) {
        while (digitalRead(CLOCK_PIN) == HIGH);
        while (digitalRead(CLOCK_PIN) == LOW);
        val <<= 1;
        val |= digitalRead(DATA_PIN);
    }
    return (val &= 0x0F);
}

Sorry this is the present code

Code:

const int CLOCK_PIN     =    2;
const int DATA_PIN      =    4;
const int PACKET_BITS   =    128;
const int PREAMBLE_LEN  =    6;
const int DATA_LEN      =    26;

enum {
    PRE_0,    PRE_1,    PRE_2,    PRE_3,    PRE_4,    PRE_5,    DATA
} states;    

byte     preamble [] = {0x0C,0x0A,0x0A,0x0C,0x01,0x0F};
char     hexAsciiVals[] = "0123456789ABCDEF";
byte     state = PRE_0;
byte     nibble;
int        nibble_count = 0;

void setup() {
  pinMode(CLOCK_PIN, INPUT);
  pinMode(DATA_PIN, INPUT);
  Serial.begin(115200);
}

void loop() {

    nibble = getNibble();
    nibble_count++;
    
//    Serial.print(digitalRead(CLOCK_PIN));
    
    switch (state) {    
        case PRE_0:
            if (nibble_count > 32) {
                // we've read 32 bytes and still not found a match
                // for the preamble so skip a clock pulse
                while (digitalRead(CLOCK_PIN) == LOW);
                while (digitalRead(CLOCK_PIN) == HIGH);
                nibble_count = 0;
            }
            else
            {
                if(nibble == preamble[0])
                      state = PRE_1;
                else
                      state = PRE_0;
            }
            break;
            
        case PRE_1:
            if(nibble == preamble[1])
                 state = PRE_2;
            else
                 state = PRE_0;    
            break;
            
        case PRE_2:
            if(nibble == preamble[2])
                state = PRE_3;
            else
                state = PRE_0;
            break;
            
        case PRE_3:
            if(nibble == preamble[3])
               state = PRE_4;
            else
               state = PRE_0;
            break;
            
        case PRE_4:
            if(nibble == preamble[4])
              state = PRE_5;
            else
              state = PRE_0;
            break;
            
        case PRE_5:
            if(nibble == preamble[5])
             state = DATA;
            else
             state = PRE_0;
            break;
            
        case DATA:
            Serial.print (hexAsciiVals[nibble]);
            if (nibble_count == DATA_LEN) {
                // all done, start again
                state = PRE_0;
                nibble_count = 0;
                Serial.println();
            }
            break;
    }
}

byte getNibble() {

    byte val = 0;
    
    for (byte bit_count = 0; bit_count < 4; bit_count++) {
        while (digitalRead(CLOCK_PIN) == HIGH);
        
          while (digitalRead(CLOCK_PIN) == LOW);
          val <<= 1;
          val |= digitalRead(DATA_PIN);
        }
    return (val &= 0x0F);
}