Hello! I am using libserialport to connect to an Arduino Uno which
controls a motor and returns some sensor data. On Linux everything
works fine. On Windows the program stutters and freezes when sending
and receiving data. The connection is running at 9600 baud.
I am using sp_blocking_write to send data, and a loop like below to
receive data:
while ( sp_input_waiting(m_connectedPort) ) {
int read = sp_blocking_read_next(m_connectedPort, buf, 256, 2);
...
}
The 'loop' is done with a QTimer triggering at 16ms or approximately
60 frames per second. I am also drawing a graph in an OpenGL view in
this 'loop' but commenting that out makes no difference.
I built the Windows libserialport with msys2 following the
instructions on the sigrok wiki, using a git clone (Mon 5 Sep 2016)
and the Linux version was built from a git clone around April 2016.
All hardware is exactly the same in both cases (I'm dual booting
between Linux and Windows on the same computer).
You can get a full description of this setup here:
https://www.youtube.com/watch?v=V3kxl4dHAwE
For the most part the receiving of data seems to be ok. When
connected, the arduino is sending sensor data non-stop and pretty much
saturates the connection. Looking at the graph as it's being drawn,
there could be some very small stutters, but this is not such a big
issue for now because...
The worst problem is when sending from the computer to the arduino,
the whole program can freeze for anywhere from half a second or so, up
to 8-10 seconds and can even show "not responding" in the window title
bar.
The sent data is very small, it's just a few bytes (usually a 7 byte
packet) to set the motor speed, and is sent a few times per second if
being controlled manually, or at most 60 times a second when the
computer is automatically controlling the motor speed.
I also tried sp_nonblocking_write. The freezing and stuttering was
cured, but the data was not sent correctly. When I look at the
transmission line with an oscilloscope, I see only a single pulse,
instead of doing the full 7 byte transmission (photo attached).
Any ideas about other things I could try?
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