Detect pattern in incoming byte stream - arduino

Question

I would like to detect a certain byte pattern in an incoming byte stream at the UART. I am using Arduino. Currently, the code detects a single \r character. On this character is detected, the byte stream before this character gets stored into a buffer. This is easy. This is my code;
int incomingByte = 0; // for incoming serial data
void setup() {
Serial.begin(9600); // opens serial port, sets data rate to 9600 bps
}
void loop() {
// send data only when you receive data:
if (Serial.available() > 0 ) {
// read the incoming byte:
incomingByte = Serial.read();
if (incomingByte != '\r') {
buffer_incoming_data[index_buffer]=incomingByte;
index_buffer++;
} else {
index_buffer = 0;
}
}
}
Here is my problem. Instead of a single character \r, I would like to detect a byte pattern that looks like this 0xAA 0xBB 0xCC. When this byte pattern is detected, the byte stream before byte pattern gets stored into a buffer.

Answer 1

Guess you invoke loop() method inside real loop operator. I can suggest next way:
int incomingByte = 0; // for incoming serial data
int pattern [] = {0xAA, 0xBB, 0xCC};
int patternIndex = 0;
int patternSize = sizeof(pattern)/sizeof(pattern[0]);
void loop() {
// send data only when you receive data:
if (Serial.available() > 0 ) {
// read the incoming byte:
incomingByte = Serial.read();
if(pattern[patternIndex] != incomingByte){
// if we found begin of pattern but didn't reach the end of it
if(patternIndex>0){
for(int i=0; i<=patternIndex-1; i++){
buffer_incoming_data[index_buffer]=pattern[i];
index_buffer++;
}
}
patternIndex = 0;
}
if(pattern[patternIndex] == incomingByte){
patternIndex++;
}else{
buffer_incoming_data[index_buffer]=incomingByte;
index_buffer++;
}
//if we reached the end of pattern
if(patternIndex==patternSize){
//do something with buffer
patternIndex = 0;
index_buffer = 0;
}
}
}
As you can see, I didn't check index_buffer for "index out of range" exception, but you should. Hope I helped you.