Raspberry Pi - Python Snap7 - Mapping and Reading Datablocks

import snap7.client
from snap7.snap7types import *
from snap7.util import *


class DBObject(object):
    pass


offsets = { "Bool":2,"Int": 2,"Real":4,"DInt":6,"String":256}

db=\
"""
Temperature Real 0.0
Cold Bool 4.0
RPis_to_Buy Int 6.0
Db_test_String String 8.0
"""

def DBRead(plc,db_num,length,dbitems):
    data = plc.read_area(areas['DB'],db_num,0,length)
    obj = DBObject()
    for item in dbitems:
        value = None
        offset = int(item['bytebit'].split('.')[0])

        if item['datatype']=='Real':
            value = get_real(data,offset)

        if item['datatype']=='Bool':
            bit =int(item['bytebit'].split('.')[1])
            value = get_bool(data,offset,bit)

        if item['datatype']=='Int':
            value = get_int(data, offset)

        if item['datatype']=='String':
            value = get_string(data, offset)

        obj.__setattr__(item['name'], value)

    return obj

def get_db_size(array,bytekey,datatypekey):
    seq,length = [x[bytekey] for x in array],[x[datatypekey] for x in array]
    idx = seq.index(max(seq))
    lastByte = int(max(seq).split('.')[0])+(offsets[length[idx]])
    return lastByte


if __name__ == "__main__":
    plc = snap7.client.Client()
    plc.connect('10.10.55.109',0,0)
    itemlist = filter(lambda a: a!='',db.split('\n'))
    deliminator='\t'
    items = [
        {
            "name":x.split(deliminator)[0],
            "datatype":x.split(deliminator)[1],
            "bytebit":x.split(deliminator)[2]
         } for x in itemlist
    ]
    #get length of datablock
    length = get_db_size(items,'bytebit','datatype')
    meh = DBRead(plc,10,length,items)
    print """
    Cold:\t\t\t{}
    Tempeature:\t\t{}
    RPis_to_Buy:\t{}
    Db_test_String:\t{}
    """.format(meh.Cold,meh.Temperature,meh.RPis_to_Buy,meh.Db_test_String)
    plc.disconnect();

Python Snap7 S7-1200 Simple Reading/Writing Memory Example

import snap7.client as c
from snap7.util import *
from snap7.snap7types import *

def ReadMemory(plc,byte,bit,datatype):
    result = plc.read_area(areas['MK'],0,byte,datatype)
    if datatype==S7WLBit:
        return get_bool(result,0,bit)
    elif datatype==S7WLByte or datatype==S7WLWord:
        return get_int(result,0)
    elif datatype==S7WLReal:
        return get_real(result,0)
    elif datatype==S7WLDWord:
        return get_dword(result,0)
    else:
        return None

def WriteMemory(plc,byte,bit,datatype,value):
    result = plc.read_area(areas['MK'],0,byte,datatype)
    if datatype==S7WLBit:
        set_bool(result,0,bit,value)
    elif datatype==S7WLByte or datatype==S7WLWord:
        set_int(result,0,value)
    elif datatype==S7WLReal:
        set_real(result,0,value)
    elif datatype==S7WLDWord:
        set_dword(result,0,value)
    plc.write_area(areas["MK"],0,byte,result)

if __name__=="__main__":
    plc = c.Client()
    plc.connect('10.10.54.2',0,1)
    print ReadMemory(plc,420,0,S7WLReal)
    WriteMemory(plc,420,0,S7WLReal,3.141592)
    print ReadMemory(plc,420,0,S7WLReal)

    #DONE!!

25+ Raspberry Compatible 1-Wire Host Boards/Hats

(sortable)

Image	Name / Link	Channels (Buses)	Extras	Price	Price per channel
	1-Wire Driver DS2482-800	8 ch.	---	£21.05	£2.63 / ch
	1-Wire Interface  Module	1 ch.	---	£5.93	£5.93 / ch
	R-Pi i2c 1-Wire OWFS Expansion Module	1 ch.	---	£17.99	£17.99 / ch
	I2C counter / 1-wire board	8 ch.	6x 16 bit Counter inputs	£69.99	£8.75 / ch
	Com Pi	1 ch.	RS232 Port	£12.99	£12.99 / ch
	1 Wire Pi Plus	1 ch.	---	£12	£12 / ch
	RP1 1-Wire GPIO Host Adapter	1 ch.	---	£7.95	£7.95 / ch
	RPI2 1-Wire Host Adapter	1 ch.	---	£14	£13.95 / ch
	RPI3 v1 1-Wire Host Adapter	8 ch.	RTC	£33	£4.12 / ch
	RPI3 v2 1-Wire Host Adapter	8 ch.	RTC	£33	£4.12 / ch
	AbioWire+	17 ch.	---	£42	£5.25 / ch
	1-Wire Mini Host	8 ch.	---	£15.26	£1.90 / ch
	1-Wire Automation System	8 ch.	expansion slot	£114	£14.25 / ch
	Raspberry Pi -9 Channel 1-Wire Board	9 ch.	RTC	£33	£3.66 / ch
	IoT-1Wire-1 module Board	8 ch.	---	£34	£4.25 / ch
	IoT-1Wire-1 module Board	1 ch. (5 ports)	---	£24	£24 / ch
	4 USB Hub & I2C AD/DA - 1-Wire   Board	1 ch.	RTC, 10bit ADC, 8bit DAC, 4 USB Hub	£52	£52 / ch
	7 USB Hub & I2C AD/DA - 1-Wire   Board	1 ch.	10bit ADC / 8bit DAC, 7 USB Hub	£58	£58 / ch
	Step Motor & I2C 1-Wire Board	1 ch.	8 ch output / step motor output	£21	£21 / ch
	One-Wire 17 Channels	17 ch.	---	£46.99	£2.76 / ch
	USB to One Wire converter	1 ch.	---	$24.60	$24.60 / ch
	S4: USB / 1-Wire Interface Card	1 ch.	---	€39	€39 / ch
	USB to 1-Wire RJ11	1 ch.	---	£26	£26 / ch
	I2C 1 Wire Click	8 ch.	---	£19.45	£2.43 / ch
	UART to 1 Wire Adapter (Retired)	1 ch.	---	---	---
	UniPi Expansion Board	1 ch.	Relays, Inputs, Outputs, Analog In/Out 0-10v	$134	$134 / ch
	PIGATOR Onewire	1 ch.	RTC, uplink header for expansion	£60	£60 / ch