Increasing data sampling rate

Projects Programming
1

HI Guys,
I am working on a simple datalogger which includes 4 different sensors and SD card.
Everything is working fine but I would like to increase the sampling rate.
Currently I am getting approximately each reading every ~800ms.
Please suggest how to optimize the code for higher sampling rate.

Thanks in advance.

2

Things to look at:

Serial.begin(9600); // could be faster
delay(50); // etc. directly or indirectly in the loop clearly slows things.
sensors.requestTemperatures(); // maybe check how fast this is
c = thermocouple.readCelsius(); // maybe check how fast this is
lcd.print("No T/C"); // etc. LCD operations are not fast. Do you need to do these every loop iteration ?

Maybe use a buffer here and consolidate to 1 write per target stream:

    logfile.print(m);           // milliseconds since start
    logfile.print(", ");
    logfile.print(c);
    logfile.print(", ");
    logfile.print(tempC);
    logfile.print(", ");
    logfile.print(P1,3);
    logfile.print(", ");
    logfile.print(P2,3);
    logfile.println();
#if ECHO_TO_SERIAL
    Serial.print(m);         // milliseconds since start
    Serial.print(", ");
    Serial.print(c);
    Serial.print(", ");
    Serial.print(tempC);
    Serial.print(", ");
    Serial.print(P1,3);
    Serial.print(", ");
    Serial.print(P2,3);
    Serial.println();
#endif //ECHO_TO_SERIAL
3

6v6gt:
Things to look at:

Serial.begin(9600); // could be faster
delay(50); // etc. directly or indirectly in the loop clearly slows things.
sensors.requestTemperatures(); // maybe check how fast this is
c = thermocouple.readCelsius(); // maybe check how fast this is

I just noticed that max6675 requires at least 200ms every cycle.
My intensional delay of 50ms adds up to 250ms (roughly).
I am still losing 550ms.

6v6gt:
Maybe use a buffer here and consolidate to 1 write per target stream:

Do you mean to write on serial and SD as a string?

Thanks.

4

Maybe look at sprintf() to format the output and pack it into a buffer for printing/storing to the SDcard.
With the 2 floats, you may have to play a trick like treating the whole number part and the decimal part as separate integers with a '.' in between. Depending on which Arduino you are using, floats may not be directly compatible with sprintf().

5

I used floattostring.h for something similar quite a long ago.

I will give it a try.
Thanks again.