How to handle data transfer from pyboard to PC

[pythoncoder]

It turns out that my boot.py had all lines commented out. With the following it works over 1K iterations.

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import pyb
pyb.usb_mode('CDC')

The distro on this laptop is Mint, which auto-mounts drives. So the SD card was mounted, but the mountpoint was unused.

So many problems seem be down to this issue.

[pythoncoder]

@Chemist You might be interested in a generalisation of this approach, which allows the program running on the Pyboard to return an arbitrary Python object which is reconstituted on the PC. This uses code from the pickle module in the Micropython library.
pb_get_object.py:

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def get_data():
    data= [i for i in range(10)]
    data.append({1:'rats', 2:'aardvark'}) # just to show we can
    return data
print(repr(get_data()))

print_object.py:

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import pyboard

def execfile(filename, device):
    pyb = pyboard.Pyboard(device)
    pyb.enter_raw_repl()
    output = pyb.execfile(filename)
    pyb.exit_raw_repl()
    pyb.close()
    return output

def loads(s):
    d = {}
    exec("v=" + s, d)
    return d["v"]

def getobject(filename, device='/dev/ttyACM0'):
    b = execfile(filename, device)
    s = b.decode('utf-8')
    return loads(s)

print(getobject('pb_get_object.py'))

Outcome:

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[adminpete@axolotl]: ~
$ python3
Python 3.4.3 (default, Oct 14 2015, 20:28:29) 
[GCC 4.8.4] on linux
Type "help", "copyright", "credits" or "license" for more information.
>>> import print_object
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, {1: 'rats', 2: 'aardvark'}]
>>> 

The ease of object serialisation in Python is one of its more endearing features

[Chemist]

I also sometimes get this error:

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OSError: [Errno 16] Device or resource busy: '/dev/pyboard'

I don't know why I get it, maybe as mentioned dhylands, this happens because I access the pyboard from two terminals for plotting data via matplotlib and bokeh(my custom web interface). In most cases it works well - ran more that 600 times with my sensor without any problems. I also uncommented this line: pyb.usb_mode('CDC') in the boot.py and will monitor its behaviour.
@Pythoncoder, I really like your generalization approach, it makes the data transfer much easier to handle.

Thanks,
Vitali

[pythoncoder]

The "Device or resource busy" message is a nuisance: in my experience it goes away if you wait a while. The device seems to start up in a busy state after the Pyboard is plugged in. The time for it to go away seems dependant on the USB port on the host machine. On my desktop boxes the device is usable after about 2 seconds. On my (fast) laptop it takes ten seconds before I can get a REPL.

It does seem an inordinately long time given that the Pyboard boots in a fraction of a second.

[dhylands]

Opening the same serial port in 2 different programs at the same time is basically asking for trouble.

Both processes will have reads pending, but a given byte of input will only go to one process or the other, and never both. Which process gets the data is "essentially random".

There is a locking protocol which is used by all of the serial terminal programs, and its on my todo list to add that to pyboard.py (at least for linux).

[tcnaks5]

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import pyboard

def execfile(filename, device='/dev/ttyACM0'):
    pyb = pyboard.Pyboard(device)
    pyb.enter_raw_repl()
    output = pyb.execfile(filename)
    pyb.exit_raw_repl()
    pyb.close()
    return output

I was able to get this working but I was wondering if there was a way to give data to the file youre running in the REPL? I have a list I want to give to the script that I want to run on the device, but it doesnt seem that I can just add it as another paramter.

Thanks for the help