I should mention I am using:
- Windows 10
- Drivers from about 2 weeks ago
- A beaglebone image from about 2 weeks ago
On Friday, April 21, 2017 at 5:18:37 PM UTC+1, David Howlett wrote:
>
> I have spent about two days tracking down an issue in one of my machines.
> I am streaming pressure readings from an i2c pressure sensor to a PC at
> high speed. I have reduced the problem to a small test case. To replicate
> the fault I connect the beaglebone black to a PC, connect to it with serial
> over the micro USB port, login and launch a command that streams data fast.
> On the PC run a program that collects the streamed data more slowly than it
> is being created.
>
> import serial
>
> x = serial.Serial('COM15')
> to_send = b'\x03yes HelloWorld\n'
> x.write(to_send)
> while True:
> received = x.readline()
> if received != b'HelloWorld\r\n':
> print(received)
>
>
> The python program above prints lines like:
>
> b'ld\r\n'
> b'HelloWoroWorld\r\n'
> b'HelloWorldorld\r\n'
> b'HelloWorldorld\r\n'
> b'ld\r\n'
> b'ld\r\n'
> b'ld\r\n'
> b'ld\r\n'
> b'ld\r\n'
> b'ld\r\n'
> b'HelloWoroWorld\r\n'
> b'ld\r\n'
> b'HelloWlloWorld\r\n'
> b'ld\r\n'
> b'HelloWorldorld\r\n'
>
> At about 4 lines per second. If I set the program on the beagle bone to
> stream slowly then this issue goes away. It appears to be an issue with a
> buffer filling up somewhere between the output of the yes command and
> reading bytes from the windows API. The correct behaviour is that the yes
> command should be stopped when the buffer is full to prevent the loss of
> data, then allowed to continue when there is space in the buffer again. I
> observe that the streaming command (in this case yes) is stopped but there
> is still data loss happening somewhere.
>
> I wrote this in python because it is the language I am most comfortable in
> but if you needed me to I could rewrite the example in some other language.
> To run the program shown above you will need pyserial and you will need to
> change 'COM15' to be whatever the port is called on your computer.
>
>
>
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