Real-Time Plotting with GNU Plot
Data Acquisition Units (DAQs) are expensive, and, in many simple cases, overkill for plotting data in real-time to see changes. For simple plotting (i.e less than 30[hz]), an Arduino with a serial connection can do the same trick. Of course, for many situations, a DAQ really is the best bet, but this plotting trick (made possible by the folks at lysium.de) is handy nevertheless. You’ll need their perl script (and a Perl installation) to make this trick work.
To stream data from the Arduino to the terminal, simply output the data via serial connection in the following format as chars:
<stream number>:<value>
Streaming one value over would be received as input looking like:
0:10
0:10
0:10
0:11
0:12
0:12
0:12
A plugged-in Arduino appears in the Linux file system in the /dev directory as /ttyUSBx or /ttyACMx where x is a positive integer.
This data can be received and redirected directly to the Perl script like so:
cat screen /dev/ttyACM0 115200 | ./driveGnuPlotStreams.pl 1 1 200 0 100
200x200+0+0 "phototransistor" 0
Note: to open a connection, I sometimes need to first run the screen command, kill the screen command, and then run the command above.