Serial buffer or faster processing?

Projects Programming
20

Fa77:
I know, and that's also the reason why at the beginning I lost many hours trying to understand what was wrong.

Nice!

The code example below might save you a little time. I would have posted it yesterday but needed to hack the snippet out of a larger sketch, which I wrote to de-serialise .conf files.

/* MattS-UK Arduino example code
    Extract key value pairs from serial stream
*/  

//if you don't want to use the Streaming library
//  you need to change  the Serial << output statements
//  to use .print, .println methods
#include <Streaming.h>

void setup()
{
	Serial.begin(9600);
	Serial << "Extract key=value pairs from serial stream...\r\n";
}

#define MAX_BUFFER_LENGTH 64
#define MAX_KEY_LENGTH 32
#define MAX_VALUE_LENGTH 32

char messageBuffer[MAX_BUFFER_LENGTH +1] = {0};
char key[MAX_KEY_LENGTH +1] = {0};
char value[MAX_VALUE_LENGTH +1] ={0};
uint16_t bufferHead = 0;

void loop()
{
	bool pairAvailable = false;
	uint16_t bytesAvailable = Serial.available();

	//buffer overrun check
	while (bytesAvailable > MAX_BUFFER_LENGTH) {
		Serial.read();
	}
	
	//sanity check
	if (bufferHead > MAX_BUFFER_LENGTH) {
		//reset the buffer
		messageBuffer[0] = 0;
		bufferHead = 0;
		return;
	}

	//read incoming
	if(bytesAvailable) {
		for(uint8_t i = 0; i < bytesAvailable; i++) {
			char inChar = Serial.read();
			if (inChar != ':') {
				messageBuffer[bufferHead++] = inChar;
			}
			else {
				//end of message.
				//Terminate the buffer and extract pair.
				messageBuffer[bufferHead] = 0;
				if(messageToPair(messageBuffer, key, value)) {
					pairAvailable = true;
				}
				else {
					Serial << "malformed message\r\n";
				}
				//reset the buffer
				messageBuffer[0] = 0;
				bufferHead = 0;
			}
		}
	}

	//process new pair
	if(pairAvailable) {
		processPair(key, value);
	}
}

//extract key = value pair from message buffer
bool messageToPair(char* message, char* key, char* value) {
	uint8_t messageLength = strlen(message);
	uint8_t valueHead = 0;
	bool keyFound = false;

	//sanity check
	if (!messageLength) {
		//failed
		key[0] = 0;
		value[0] = 0;
		return false;
	}

	//split key = value pair
	for (uint8_t i = 0; i < messageLength; i++){
		if ((!keyFound) && (i < MAX_KEY_LENGTH)) {
			key[i] = message[i];
			if(message[i] == '='){
				keyFound = true;
				key[i] = 0;
			}
		}
		else {
			value[valueHead++] = message[i];
		}
	}
	value[valueHead] = 0;

	//sanity check
	if((!keyFound) || (strlen(value) > MAX_VALUE_LENGTH)) {
		//fail
		key[0] = 0;
		value[0] = 0;
		return false;
	}
	return true;
}

//example pair processing rule
void processPair(char* key, char* value) {
	Serial << "Key=" << key << "\tValue=" << value << "\r\n";

	if(key[0] = 'L') {
		//device is an LED
		uint8_t ledID = atoi(&key[1]);
		bool ledState = (bool) atoi(value);
		Serial << " ledID = " << ledID  << "\tstate = " << ledState << "\r\n";
		return;
	}
}