While True loop Stopping

[darkglove]

My While True loop runs once and then keeps stopping at

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data = stdin.buffer.read(1)

until it receives something else

I did try

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if stdin.buffer.read(1) != "": data = stdin.buffer.read(1)

but that doesn't help

If there is a problem with

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data = stdin.buffer.read(1)

then shouldn't it thow an exception? It doesn't...

I need it to keep looping so that is will run

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if received_msg:

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while True:
    try:
        print("Here 1")
        data = stdin.buffer.read(1)
        print("Here 2")
        gatheredData.extend(data)
        if str(data.decode()) == "\r":
            xbee.transmit(addr16 if addr16 else addr64, gatheredData)
            gatheredData = bytearray(b'')
        received_msg = xbee.receive()
        if received_msg:
            payload = received_msg['payload']
            print("%s" % (payload.decode()))
    except Exception as e:
        print("Nope")

[dhylands]

stdin doesn't have an any() method, so you can either use the USB_VCP device or UART device depending on which microprocessor you're using.

http://docs.micropython.org/en/latest/l ... SB_VCP.any
http://docs.micropython.org/en/latest/l ... e.UART.any

I normally wrap these accesses up in my own class, along these lines:
https://github.com/dhylands/json-ipc/bl ... sb_port.py

Test code for host side
https://github.com/dhylands/json-ipc/bl ... al_port.py

You might also be able to use uasyncio (unfortunately I haven't played with this much so I'm not sure if it works with stdin or not).

[pythoncoder]

...
You might also be able to use uasyncio (unfortunately I haven't played with this much so I'm not sure if it works with stdin or not).

As a cooperative scheduler uasyncio won't rescue you from a blocking method like stdin.buffer.read(1). Its stream I/O mechanism works well with UARTs. Doubtless it will work with the VCP interface but I haven't tried it.

The other option is to use threading but that is a last resort in my opinion.

[darkglove]

Thank you both for your replies.

I'm newbing my way through this and still not sure which way to go

This code is running on an XBee3

The documentation says for UART to use stdin.

I can't use UART as it doesn't exist if I try to import it, these are in a 232 shield so that would mean the USB_VCP is out, right?

[dhylands]

That same documentation also tells you how to do a non-blocking read.

[darkglove]

Of course it does.

So I now know what blocking means!

Thankyou

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data = stdin.buffer.read(-1)
if str(data) != "None":
    etc

Working

[dhylands]

It would be more efficient to just use:

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  if data:

rather than converting data to a string, or perhaps using

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if data is not None:

Be aware that read may return more than 1 byte, so be prepared for that scenario.

[darkglove]

I did actually try

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 if data:

but it didn't work, though this might have been for another problem and I fixed the wrong thing...

I also thought about the

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if data is not None:

but stopped when it was working!

Will have a play to make more efficient.

Also, yes, I immediately noticed that I received multiple bytes which works better for me anyway.

Thanks