Der IskraEmeco MT171 kann auch nach EN 62056-21 über die IR-Schnittstelle ausgelesen werden.

Man benötigt den IR-Schreib-Lese-Kopf, da der Zähler erst angesprochen werden muss, bevor er sendet.

Hier ist die typische IR-Schnittstelle zu sehen.
Unter der markierten(⇒) Öffnung befindet sich der Empfänger.
Darüber muß also die IR-LED des Opto-Kopfes positioniert werden.

Die S0-Schnittstelle (blinkende rote LED auf der Frontseite) wurde bisher nicht getestet.
Da hier vermutlich automatisch eine Summenbildung zwischen bezogener Energie und eingespeister Energie stattfindet, finde ich das erstmal weniger interessant.

es soll zwei interne S0 Schnittstellen geben. Bisher ist mir nicht bekannt, ob hier dann zwischen Einspeisung und Bezug unterschieden wird.
Diese Schnittstellen liegen hinter der Verplombung und sind mir nicht zugänglich.

Das Auslesen der Daten über die IR-Schnittstelle wird wie hier beschrieben eingeleitet.
Der Zähler antwortet mit

/ISk5MT171-0222

Der am Ende zurückgelieferte Datensatz

0-0:C.1.0*255(4744xxxx)
1-0:0.0.0*255(458xxxx)
1-0:0.2.0*255(V1.0)
1-0:1.8.0*255(007206.0 kWh)
1-0:2.8.0*255(005313.4 kWh)
0-0:F.F.0*255(00000000)
!

Leider keine Momentanwerte oder zusätzliche Infos.
Ob und wie man an zusätzliche Messwerte gelangt, ist mir bisher nicht bekannt.

See here python code that reads the meter data about every 5 seconds and writes a line to file is the meter data has changed. It uses py-serial.

from __future__ import print_function 
import serial
import time

def send(port, bytes, tr):
  """ sends an command to serial and reads and checks the echo
      port  - the open serial port
      bytes - the string to be send
      tr    - the responce time
  """
  #print("start send")  
  port.write(bytes)
  time.sleep(tr)
  echo = port.read(len(bytes))
  if (echo != bytes):
    print("echo is not same as send:", bytes, " vs ", echo)
  #print("end send")

def read_datablock():
  ACK = '\x06'
  STX = '\x02'
  ETX = '\x03'
  tr = 0.2
  """ does all that's needed to get meter data from the meter device """ 
  try:
    IskraMT171=serial.Serial(port='/dev/ttyUSB0', baudrate=300, bytesize=7, parity='E', stopbits=1, timeout=1.5); # open port at specified speed
    # 1 ->
    time.sleep(tr)
    Request_message='/?!\r\n' # IEC 62056-21:2002(E) 6.3.1
    send(IskraMT171, Request_message, tr)
    # 2 <-
    time.sleep(tr)
    Identification_message=IskraMT171.readline() # IEC 62056-21:2002(E) 6.3.2
    if (Identification_message[0] != '/'):
      print("no Identification message")
      IskraMT171.close()
      return ""
    if (len(Identification_message) < 7):
      print("Identification message to short")
      IskraMT171.close()
      return ""
    if (Identification_message[4].islower()):
      tr = 0.02
    manufacturers_ID = Identification_message[1:4]
    if (Identification_message[5] == '\\'):
      identification = Identification_message[7:-2]
    else:
      identification = Identification_message[5:-2]
    speed = Identification_message[4]
    #print("speed = ", speed)
    if (speed == "1"): new_baud_rate = 600
    elif (speed == "2"): new_baud_rate = 1200
    elif (speed == "3"): new_baud_rate = 2400
    elif (speed == "4"): new_baud_rate = 4800
    elif (speed == "5"): new_baud_rate = 9600
    elif (speed == "6"): new_baud_rate = 19200
    else:
      new_baud_rate = 300
      speed = "0"
    #print(manufacturers_ID, " ", identification, " speed=", speed)
    # 3 ->
    Acknowledgement_message=ACK + '0' + speed + '0\r\n' # IEC 62056-21:2002(E) 6.3.3
    send(IskraMT171, Acknowledgement_message, tr)
    IskraMT171.baudrate=new_baud_rate
    time.sleep(tr)
    # 4 <-
    datablock = ""
    if (IskraMT171.read() == STX):
      x = IskraMT171.read()
      BCC = 0
      while (x  != '!'):
        BCC = BCC ^ ord(x)
        datablock = datablock + x
        x = IskraMT171.read()
      while (x  != ETX):
        BCC = BCC ^ ord(x) # ETX itself is part of block check
        x = IskraMT171.read()
      BCC = BCC ^ ord(x)
      x = IskraMT171.read() # x is now the Block Check Character
      # last character is read, could close connection here
      if (BCC != ord(x)): # received correctly?
        datablock = ""
        print("Result not OK, try again")
    else:
      print("No STX found, not handled.")
    IskraMT171.close()
    return datablock
  except:
    print("Some error reading data")
    if (IskraMT171.isOpen()):
      IskraMT171.close()
    return ""

def meter_data(datablock, map, header):
  """ takes a datablock as received from the meter and returns a list with requested meter data as set in map
      if header != 0 a list with data type and units is returned """
  line = []
  ## initialise line
  for l in range(len(map)):
    if (header == 1):
      line.append(map[l][1])
    elif (map[l][0] == "time"):
      line.append(time.strftime("%Y-%m-%d %H:%M:%S"))
    else:
      line.append("")
  datasets = datablock.split('\n')
  for dataset in datasets:
    if (dataset != ""):
      x = dataset.split('(')
      address = x[0]
      x = x[1][:-2].split(' ') # the standard seems to have a '*' instead of ' ' here
      value = x[0]
      try:
        unit = '['+x[1]+']'
      except:
        unit = ""
      for l in range(len(map)):
        if (map[l][0] == address):
          if (header == 0):
            line[l] = value
          else:
            line[l] = map[l][1] + unit
          break;
  return line

def output(filename, line):
  f = open(filename, "a")
  print(line, file=f)
  f.close()

map = [
  # The structure of the meter_data() output can be set with this variable 
  # first string on each line is the cosim adress of the data you want to safe or "time" to insert the time
  # the second string on each line is a description of the type of data belonging to the cosim address
  # the order of the lines sets the order of the meter_data() output
  # example
  # header: ['meter ID', 'datum & tijd', 'verbruik totaal[kWh]', 'verbruik tarief1[kWh]', 'verbruik tarief2[kWh]', 'terug totaal[kWh]', 'terug tarief1[kWh]', 'terug tarief2[kWh]']
  # data: ['12345678', '2013-02-08 10:08:41', '0054321', '0000000', '0054321', '0000000', '0000000', '0000000']
  ["1-0:0.0.0*255", "meter ID"],
  ["time", "datum & tijd"],
  ["1-0:1.8.0*255", "verbruik totaal"],
  ["1-0:1.8.1*255", "verbruik tarief1"],
  ["1-0:1.8.2*255", "verbruik tarief2"],
  ["1-0:2.8.0*255", "terug totaal"],
  ["1-0:2.8.1*255", "terug tarief1"],
  ["1-0:2.8.2*255", "terug tarief2"]
]

example_datablock = """0-0:C.1.0*255(12345678)
1-0:0.0.0*255(12345678)
1-0:0.2.0*255(V1.0)
1-0:1.8.0*255(0054321 kWh)
1-0:1.8.1*255(0000000 kWh)
1-0:1.8.2*255(0054321 kWh)
1-0:2.8.0*255(0000000 kWh)
1-0:2.8.1*255(0000000 kWh)
1-0:2.8.2*255(0000000 kWh)
FF(00000000)
"""

#print(meter_data(example_datablock , map, 1))
#print(meter_data(example_datablock , map, 0))

file = "meterdata.txt"
previous_data = ""
data = read_datablock()

output(file, meter_data(data , map, 1)) # header
while (1):
  if (data == ""):
    print(time.strftime("%Y-%m-%d %H:%M:%S"), "No data received")
  elif (previous_data != data):
    output(file, meter_data(data , map, 0))
    previous_data = data
  time.sleep(3) # minimum waiting time is 3 seconds, less and the meter doesn't return data 
  data = read_datablock()

Example output is:

['meter ID', 'datum & tijd', 'verbruik totaal[kWh]', 'verbruik tarief1[kWh]', 'verbruik tarief2[kWh]', 'terug totaal[kWh]', 'terug tarief1[kWh]', 'terug tarief2[kWh]']
['12345678', '2013-02-09 12:49:14', '0011540', '0000000', '0011540', '0000000', '0000000', '0000000']
['12345678', '2013-02-09 13:00:45', '0011541', '0000000', '0011541', '0000000', '0000000', '0000000']
['12345678', '2013-02-09 13:18:06', '0011542', '0000000', '0011542', '0000000', '0000000', '0000000']
['12345678', '2013-02-09 13:40:14', '0011543', '0000000', '0011543', '0000000', '0000000', '0000000']
['12345678', '2013-02-09 13:57:53', '0011544', '0000000', '0011544', '0000000', '0000000', '0000000']
['12345678', '2013-02-09 14:15:16', '0011545', '0000000', '0011545', '0000000', '0000000', '0000000']
['12345678', '2013-02-09 14:53:29', '0011546', '0000000', '0011546', '0000000', '0000000', '0000000']

Only change

map

in order to change header names, to add or remove what data is saved or to change the order.

[1] MT171
[2] Elster AS1440