utils.py

# -*- coding: utf-8 -*-
#!/usr/bin/env python
"""
    Utility Functions.
    
    @author g4b
"""
import sys



if sys.version_info[0] == 2:
    def is_stringlike(v):
        return isinstance(v, basestring)

    def ensure_bytes(v):
        if isinstance(v, unicode):
            return str(v)
        if isinstance(v, list):
            return bytearray(v)
        return v
else:
    def is_stringlike(v):
        return isinstance(v, str) or isinstance(v, bytes)

    def ensure_bytes(v):
        if isinstance(v, str):
            return bytearray(ord(c) for c in v)
        if isinstance(v, list):
            return bytearray(v)
        return v



def detect_pt(device='/dev/ttyUSB0', timeout=2, silent=True,
              ecr=None):
    """ connects to given serial port and tests if a PT is present.
        if present: tries to return version number or True
        returns False otherwise.
        
        @param timeout: set the timeout to have a faster response time.
        @param silent: if False, exceptions won't be caught, default: True.
        @param ecr: give a working ecr to perform this task. note: you have to
            reconnect the transport since the timeout is changed.
    """
    from ecrterm.ecr import ECR  # avoid circular import
    from ecrterm import packets

    def __detect_pt(port, timeout, ecr):
        e = ecr or ECR(port)
        # reconnect to have lower timeout
        e.transport.close()
        e.transport.connect(timeout=timeout)
        errors = e.transmit(packets.StatusEnquiry())
        try:
            if not errors:
                if isinstance(e.last.completion, packets.Completion):
                    return e.last.completion.fixed_values.get('sw-version', True) or True
                return True
            return False
        finally:
            # Reset timeout
            e.transport.close()
            e.transport.connect()
    if silent:
        try:
            return __detect_pt(device, timeout, ecr)
        except:
            return False
    else:
        return __detect_pt(device, timeout, ecr)

if __name__ == '__main__':
    if detect_pt():
        print("PT is online at ttyUSB0")
    else:
        print("PT cant be found at ttyUSB0")