https://automatizace.hw.cz/mbus-meterbus-zakladni-popis-komunikacniho-modelu

http://elektro.tzb-info.cz/merici-a-regulacni-technika/9539-instalace-komunikacni-sbernice-m-bus-1-cast

https://domat-int.com/wp-content/uploads/2012_12_IDB_SK_Instalace_M-Bus.pdf

http://www.m-bus.com/

http://www.m-bus.com/mbusdoc/md4.php


https://www.promotic.eu/cz/pmdoc/Subsystems/Comm/Protocol/MBUS.htm



Ale to nahote je m-BUS !!!!   mozna neco jineho nez modbus  - dole 


http://home.zcu.cz/~ronesova/bastl/files/modbus.pdf


http://www.modbus.org/

http://www.simplymodbus.ca/FAQ.htm

https://www.rtaautomation.com/technologies/modbus-rtu/

https://www.promotic.eu/cz/pmdoc/Subsystems/Comm/PmDrivers/kModbusMr.htm?gclid=CjwKCAiA24PVBRBvEiwAyBxf-TOKYO9-FAza8ynE2njCLMuFIh-EFDNBPpnRvzVx8L_2P6feNEe-wxoCQGkQAvD_BwE

https://automatizace.hw.cz/clanek/2004082301

https://cs.wikipedia.org/wiki/Modbus#P%C5%99enosov%C3%A1_media,_verze_protokolu

http://www.modbus.org/docs/Modbus_over_serial_line_V1.pdf

specifikace modbusu 
http://www.modbus.org/specs.php

http://www.modbus.org/docs/Modbus_over_serial_line_V1_02.pdf





3.4.4 Grounding Arrangements
The « Common » circuit ( Signal and optional Power Supply Common ) must be connected directly to protective ground, preferably at
one point only for the entire bus. Generally this point is to choose on the master device or on its Tap.

TAkže u naší kotelnz jsme v háji !  má plovoucí zem 


Line termination may be a 150 ohms value ( 0.5 W ) resistor.

If one or several devices need polarization, one pair of resistors must be connected on the RS-485 balanced pair :
- a Pull-Up Resistor to a 5V Voltage on D1 circuit,
- a Pull-Down Resistor to the common circuit on D0 circuit.
The value of those resistors must be between 450 Ohms and 650 Ohms. 650 Ohms resistors value may allow a higher number of
devices on the serial line bus.



3.6 Cables
A MODBUS over Serial Line Cable must be shielded. At one end of each cable its shield must be connected to protective ground. If
a connector is used at this end, the shell of the connector is connected to the shield of the cable.
An RS485-MODBUS must use a balanced pair (for D0-D1) and a third wire (for the Common).

Heyký, že musí být stíněn, ale kde je na to pin ? 
barvy drátů strana 32 

D1-TXD1 yellow
D0-TXD0 brown
Common grey



LED strana 32 
žlutá  komunikuje se
červená  error


strana 35  
6.1 Appendix A - Management of Serial Line Diagnostic Counters





knihovna pro Linux
http://libmodbus.org/


to má být pro mikrokontrolery   
https://sourceforge.net/projects/freemodbus.berlios/



hodíš do Googu
MODBUS Microchip

a vzleze asi tak 1000 odkazů 


tohle  ještě chce spoustu dalšího  
http://www.microchip.com/wwwAppNotes/AppNotes.aspx?appnote=en566544

https://www.microchip.com/SWLibraryWeb/product.aspx?product=TCPIPSTACK

a tohle jim nefunguje 
http://www.microchip.com/SWLibraryWeb/product.aspx?product=TCPIPSTACK





možná ? 
http://www.embeddedcodesource.com/search?searchterm=modbus&type=all

tady se zobrazí tuna odkazů 
http://www.microchip.com/wwwAppNotes/AppNotes.aspx?appnote=en573940






https://www.freemodbus.org/

a tadz se to dá kopuit 
https://www.embedded-solutions.at/products-services/modbus



------------------------------------

Protokol 
http://www.modbus.org/docs/Modbus_Application_Protocol_V1_1b3.pdf

The  Internet  community  can  access  MODBUS  at    a  reserved 
system port 502 on the TCP/IP stack.  



http://www.microchip.com/forums/m346219.aspx



tohle vypadá dost dobře 
http://www.simplymodbus.ca/TCP.htm


popis protokolu 
https://www.rtaautomation.com/technologies/modbus-tcpip/


tady by se asi neco dalo najit 
https://www.ccsinfo.com/forum/viewtopic.php?p=180169


https://www.codebus.net/d-bMXI.html
asi jo, chtějí sign in  


https://github.com/Kliemann-Service-GmbH/CO-NO2-Kombisensor-Mod/find/master





modbus_phy_layer_ascii.c
modbus_phy_layer_rtu.c
modbus_phy_layer_tcpip.c
modbus_phy_layer_tcpip.h
modbus.c
modbus.h
modbus_app_layer.c
modbus_app_layer.h
modbus_app_layer_tcpip.c
modbus_app_layer_tcpip.h
modbus_phy_layer.h
    

a našel jsem to také tady      
https://github.com/Kliemann-Service-GmbH/CO-NO2-Kombisensor-Mod/find/master




a nějaké softwarové udělátko na MODBUS ovet serial 
http://www.simplymodbus.ca/RTUmaster.htm
    
    
https://www.modbustools.com/


https://sourceforge.net/projects/qmodmaster/

Možná tohle ???   
https://automationforum.in/t/modbus-test-utility-free-alternative-to-modscan-modbus-poll-simply-modbus/2828