Reading a Serial Port - Ignore portion of data written to serial port for certain time

Posted by farmerjoe on Stack Overflow See other posts from Stack Overflow or by farmerjoe
Published on 2013-11-09T09:54:53Z Indexed on 2013/11/09 15:54 UTC
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I would like to read data coming and Arduino on a serial port on intervals. So essentially something like

  1. Take a reading
  2. Wait
  3. Take a reading
  4. Wait
  5. Take ...

etc.

The problem I am facing is that the port will buffer its information so as soon as I call a wait function the data on the serial port will start buffering. Once the wait function finishes I try and read the data again but I am reading from the beginning of the buffer and the data is not current anymore, but instead is the reading taken at roughly the time the wait function began.

My question is whether there is a way that I am unaware of to ignore the portion of data read in during that wait period and only read what is currently being delivered on the serial port?

I have this something analogous to this so far:

import serial

s = serial.Serial(path_to_my_serial_port,9600)

while True:
    print s.readline()
    time.sleep(.5)

For explanation purposes I have the Arduino outputting the time since it began its loop. By the python code, the time of each call should be a half second apart. By the serial output the time is incrementing in less than a millisecond. These values do not change regardless of the sleep timing.

Sample output:

504

504

504

504

505

505

505

...

As an idea of my end goal, I would like to measure the value of the port, wait a time delay, see what the value is then, wait again, see what the value is then, wait again.

I am currently using Python for this but am open to other languages.

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