currentvolt.py

from pymodbus.constants import Endian
from struct import pack, unpack
from pymodbus.constants import Endian
from pymodbus.utilities import pack_bitstring
from pymodbus.utilities import unpack_bitstring
from pymodbus.exceptions import ParameterException
from pymodbus.client.sync import ModbusSerialClient as ModbusClient
from pymodbus.transaction import ModbusSocketFramer as ModbusFramer
import datetime
import time
import sys
import os
import logging
import logging.handlers
from os.path import join

ID_VENDOR = '0403'
ID_PRODUCT = '6001'


class BinaryPayloadDecoder(object):

    '''  A utility that helps decode payload messages from a modbus
    reponse message.  It really is just a simple wrapper around
    the struct module, however it saves time looking up the format
    strings. What follows is a simple example::

        decoder = BinaryPayloadDecoder(payload)
        first   = decoder.decode_8bit_uint()
        second  = decoder.decode_16bit_uint()
    '''

    def __init__(self, payload, endian=Endian.Little):
        ''' Initialize a new payload decoder

        :param payload: The payload to decode with
        :param endian: The endianess of the payload
        '''
        self._payload = payload
        self._pointer = 0x00
        self._endian = endian

    @classmethod
    def fromRegisters(klass, registers, endian=Endian.Little):
        ''' Initialize a payload decoder with the result of
        reading a collection of registers from a modbus device.

        The registers are treated as a list of 2 byte values.
        We have to do this because of how the data has already
        been decoded by the rest of the library.

        :param registers: The register results to initialize with
        :param endian: The endianess of the payload
        :returns: An initialized PayloadDecoder
        '''
        if isinstance(registers, list):  # repack into flat binary
            payload = ' '.join(pack('>H', x) for x in registers)
            return klass(payload, endian)
        raise ParameterException('Invalid collection of registers supplied')

    @classmethod
    def fromCoils(klass, coils, endian=Endian.Little):
        ''' Initialize a payload decoder with the result of
            reading a collection of coils from a modbus device.

        The coils are treated as a list of bit(boolean) values.

        :param coils: The coil results to initialize with
        :param endian: The endianess of the payload
        :returns: An initialized PayloadDecoder
        '''
        if isinstance(coils, list):
            payload = pack_bitstring(coils)
            return klass(payload, endian)
        raise ParameterException('Invalid collection of coils supplied')

    def reset(self):
        ''' Reset the decoder pointer back to the start
        '''
        self._pointer = 0x00

    def decode_8bit_uint(self):
        ''' Decodes a 8 bit unsigned int from the buffer
        '''
        self._pointer += 1
        fstring = self._endian + 'B'
        handle = self._payload[self._pointer - 1:self._pointer]
        return unpack(fstring, handle)[0]

    def decode_bits(self):
        ''' Decodes a byte worth of bits from the buffer
        '''
        self._pointer += 1
        fstring = self._endian + 'B'
        handle = self._payload[self._pointer - 1:self._pointer]
        return unpack_bitstring(handle)

    def decode_16bit_uint(self):
        ''' Decodes a 16 bit unsigned int from the buffer
        '''
        self._pointer += 2
        fstring = self._endian + 'H'
        handle = self._payload[self._pointer - 2:self._pointer]
        return unpack(fstring, handle)[0]

    def decode_32bit_uint(self):
        ''' Decodes a 32 bit unsigned int from the buffer
        '''
        self._pointer += 4
        fstring = self._endian + 'I'
        handle = self._payload[self._pointer - 4:self._pointer]
        return unpack(fstring, handle)[0]

    def decode_64bit_uint(self):
        ''' Decodes a 64 bit unsigned int from the buffer
        '''
        self._pointer += 8
        fstring = self._endian + 'Q'
        handle = self._payload[self._pointer - 8:self._pointer]
        return unpack(fstring, handle)[0]

    def decode_8bit_int(self):
        ''' Decodes a 8 bit signed int from the buffer
        '''
        self._pointer += 1
        fstring = self._endian + 'b'
        handle = self._payload[self._pointer - 1:self._pointer]
        return unpack(fstring, handle)[0]

    def decode_16bit_int(self):
        ''' Decodes a 16 bit signed int from the buffer
        '''
        self._pointer += 2
        fstring = self._endian + 'h'
        handle = self._payload[self._pointer - 2:self._pointer]
        return unpack(fstring, handle)[0]

    def decode_32bit_int(self):
        ''' Decodes a 32 bit signed int from the buffer
        '''
        self._pointer += 4
        fstring = self._endian + 'i'
        handle = self._payload[self._pointer - 4:self._pointer]
        return unpack(fstring, handle)[0]

    def decode_64bit_int(self):
        ''' Decodes a 64 bit signed int from the buffer
        '''
        self._pointer += 8
        fstring = self._endian + 'q'
        handle = self._payload[self._pointer - 8:self._pointer]
        return unpack(fstring, handle)[0]

    def decode_32bit_float(self):
        ''' Decodes a 32 bit float from the buffer
        '''
        self._pointer += 4
        fstring = self._endian + 'f'
        handle = self._payload[self._pointer - 4:self._pointer]
        return unpack(fstring, handle)[0]

    def decode_64bit_float(self):
        ''' Decodes a 64 bit float(double) from the buffer
        '''
        self._pointer += 8
        fstring = self._endian + 'd'
        handle = self._payload[self._pointer - 8:self._pointer]
        return unpack(fstring, handle)[0]

    def decode_string(self, size=1):
        ''' Decodes a string from the buffer

        :param size: The size of the string to decode
        '''
        self._pointer += size
        return self._payload[self._pointer - size:self._pointer]


def find_tty_usb(idVendor, idProduct):
    """find_tty_usb('067b', '2302') -> '/dev/ttyUSB0'"""
    # Note: if searching for a lot of pairs, it would be much faster to search
    # for the enitre lot at once instead of going over all the usb devices
    # each time.
    for dnbase in os.listdir('/sys/bus/usb/devices'):
        dn = join('/sys/bus/usb/devices', dnbase)
        if not os.path.exists(join(dn, 'idVendor')):
            continue
        idv = open(join(dn, 'idVendor')).read().strip()
        if idv != idVendor:
            continue
        idp = open(join(dn, 'idProduct')).read().strip()
        if idp != idProduct:
            continue
        for subdir in os.listdir(dn):
            if subdir.startswith(dnbase + ':'):
                for subsubdir in os.listdir(join(dn, subdir)):
                    if subsubdir.startswith('ttyUSB'):
                        return join('/dev', subsubdir)


def read_current_register(client, address, count=1, unit=146):
    """Reads the current register

    Parameters
    ----------

    address : Address of the register
    count: Number of registers to read 
    unit: Unit of hardware

    Returns
    -------
    current: float 
    """
    regObject = client.read_holding_registers(
        address=address, count=count, unit=unit)
    decoder = BinaryPayloadDecoder.fromRegisters(
        regObject.registers, endian=Endian.Big)
    after_decimal = decoder.decode_16bit_uint()
    decoder = BinaryPayloadDecoder.fromRegisters(
        regObject.registers, endian=Endian.Big)
    before_decimal = decoder.decode_8bit_int()
    if (after_decimal % 1000) > 500:
        before_decimal -= 1
    current = before_decimal + (after_decimal % 1000) / 1000.0
    return current


def main():
    METER_PORT = "/dev/ttyUSB0"
    # print METER_PORT#reading to which port rs485(client) is connected
    client = ModbusClient(method='rtu', port=METER_PORT, baudrate=9600,
                          stopbits=1, parity='E', timeout=0.3, bytesize=8)
    client.connect()
    f = open("abc.csv", "w")

    while True:
        try:
            row = str(datetime.datetime.now())
            for register in range(10, 23):
                current = read_current_register(client, register)
                row += "," + str(current)
            row += ",\n"
            f.write(row)

        except Exception as e:
            print "Internal Exception: Meter: " + '\n' + e.__str__()

            client = None


if __name__ == "__main__":
    main()