8

Assume you want to offer an interface for other programmers, that enables them to write code like that:

# connect to remote Linux device
>>> conn = myClass('/dev/ttyUSB0', 115200, '8N1')
>>> conn.login('myname', 'mypass')
>>> output = conn.command('ls -al')
>>> print output
total 3
drwxr-xr-x 49 myname  myname   4096 Jun 21 15:13 .
drwxr-xr-x  4 root    root     4096 Mar 20 14:43 ..
drwxr-xr-x 49 myname  myname   1005 Jun 14 11:23 .vimrc
>>> output2 = conn.command('cd ..')
>>> print output2

>>>

How would you go about implementing it?

Current Status

I first thought about pyserial, but it seems to treat the serial connection simply as a file like object, not like a terminal. I found from it's source code that pyserial itself uses termios, which at least seems to enable some terminal like configuration options. But which framework enables terminal-like IO? I'm just a beginner in this whole embedded system world in general, but until now it seems to me as if terminal IO via serial connection should be a common daily problem in this environment and there should be already a framework doing the "hard work". But till now I failed to find it.

Background

At the moment most people in my company test their embedded system development topics manually. But we want to switch to a more automatic scenario with a lot of unittest like scripting. Because we already have a terminal like interface per UART on our embedded systems I'd like to give the authors of those test scripts the opportunity to write code more intuitively as they would have interacted with the devices via minicom or screen anyway.

erikbstack
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    A terminal is rightly treated like a file. You write to it, you read from it; you have little else to do with it. I suppose you're not interested in handling hardware flow control from within your app. On this foundation it is relatively easy to create what you wanted: write until EOL, read until EOF, rinse, repeat. – 9000 Jun 21 '13 at 14:48

2 Answers2

2

I would strongly consider looking into Twisted and the projects using Twisted for Python projects talking to terminals. I have seen a terminal screen scraper written on Twisted, and at least one public telnet client on GitHub - https://github.com/fjogstad/twisted-telnet-client.

I'm not sure which terminal interface you are trying to talk to, but here at least is an example of a terminal emulator in Twisted: https://launchpad.net/python-tvi955.

A nice thing about using an asynchronous framework like Twisted would be that you could have one test server driving testing on several virtual machines or physical machines in parallel.

pcurry
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  • *edit*: my question was the following but I guess I can google that myself. "Well, how would I find out which terminal interface the device speaks?" – erikbstack Jun 21 '13 at 15:11
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    I don't know, my work in and around Twisted is primarily in asynchronous HTTP interactions, rather than writing TTY interface code. Twisted's API documentation is here - http://twistedmatrix.com/documents/current/api/twisted.html - and it looks like [conch](http://twistedmatrix.com/documents/current/api/twisted.conch.html) is their shell emulator of choice, working over SSH. – pcurry Jun 21 '13 at 15:24
-2

DOESN'T ADDRESS THE SPECIFIC QUESTION, but most likely you google it to get the following:

If you want to actually interact with serial i/f consider to use: pyserial (pip install pyserial):

here is an example:

import serial

ser = serial.Serial(
    port='/dev/ttyUSB1',
    baudrate=9600,
    parity=serial.PARITY_ODD,
    stopbits=serial.STOPBITS_TWO,
    bytesize=serial.SEVENBITS
)

ser.open()


ser.write("bla bla" + '\r')
0x90
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