from pymodbus.client.sync import ModbusSerialClient
from pymodbus.pdu import ExceptionResponse
from pymodbus.exceptions import ModbusIOException
import RS485Ext
import struct
import time

def registersToIeeeFloat(i):
  return struct.unpack('f', bytes(
                                   [((x & 0xff00) >> 8) if y else (x & 0x00ff) 
                                     for x in i[::-1] 
                                     for y in [False, True]
                                   ]
                                 )
                      )[0]

def registersToIeeeFloatReverse(i):
  return struct.unpack('f', bytes(
                                   [((x & 0xff00) >> 8) if y else (x & 0x00ff) 
                                     for x in i 
                                     for y in [False, True]
                                   ]
                                 )
                      )[0]

def dataConverter(t, d):
  if t == 'F':
    return registersToIeeeFloat(d)
  elif t == 'RF':
    return registersToIeeeFloatReverse(d)
  else:
    raise Exception("Converter '{0}' is not supported".format(t))


class ModbusException(Exception):
  def __init__(self, resp):
    self.msg = str(result)

  def __str__(self):
    return self.msg

class ModbusRequestDefinition(object):
  def __init__(self, unit, address, count, converter, label):
    self.unit = unit
    self.address = address
    self.count = count
    self.converter = converter
    self.label = label
  
reqs = [
  ModbusRequestDefinition(4, 0x2000, 2, 'F', '(ERR) Unavailable device'),
  ModbusRequestDefinition(1, 0x2000, 4, 'F', '(ERR) Wrong register size'),
  ModbusRequestDefinition(1, 0x2000, 2, 'F', 'Voltage'),
  ModbusRequestDefinition(1, 0x2020, 2, 'F', 'Frequency'),
  ModbusRequestDefinition(1, 0x2060, 2, 'F', 'Current'),
  ModbusRequestDefinition(3, 0x0004, 2, 'RF', 'Resistance Channel 1'),
  ModbusRequestDefinition(3, 0x000C, 2, 'RF', 'Temperature Channel 1'),
  ModbusRequestDefinition(3, 0x0014, 2, 'RF', 'Resistance Channel 2'),
  ModbusRequestDefinition(3, 0x001C, 2, 'RF', 'Temperature Channel 2'),
]


def getSerial():
  return RS485Ext.RS485Ext(port='/dev/ttyAMA0', baudrate=1200, stopbits=1,
                           timeout=1)

client = ModbusSerialClient(method='rtu')
client.socket = getSerial()
client.connect()

delay = 0.05

while True:
  for req in reqs:
    try:
      time.sleep(delay)
      # print("Trying to read: {0} {1} {2}".format(req.address, req.count, req.unit))
      result = client.read_holding_registers(address=req.address, 
                                             count=req.count, 
                                             unit=req.unit)
      if type(result) in [ExceptionResponse, ModbusIOException]:
        raise ModbusException(result)
      print("{0}: {1:.2f}".format(req.label, 
                                  dataConverter(req.converter, 
                                                result.registers)))
    except ModbusException as e:
      print("ERROR when querying '{0}': {1!s}".format(req.label, e))
      if client.socket is None:
        print("renew socket")
        client.socket = getSerial()

  print("-------------")
  time.sleep(10)


client.close()